A Review of Drive Techniques for Multiphase Machines
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paper_title: Multilevel Converter/Inverter Topologies and Applications

paper_content:

This chapter is dedicated to explaining the basic concept of multilevel converter/inverters, introducing the three typical topologies, i.e., diode clamped multilevel inverter, flying capacitor multilevel inverter, and cascade multilevel inverter (CMI), and describing their pros and cons regarding their most suitable applications. A generalized multilevel inverter topology unifies the three typical multilevel inverters and has the ability to generate other multilevel topologies, such as modular multilevel converter (M2C), magnetic‐less multilevel DC‐DC converters, and stacked multicell converters, etc. As application examples, Y‐connection, Δ‐connection, and face‐to‐face‐connected CMIs are applied to static var generation (SVG), static synchronous compensator (STATCOM), and flexible AC transmission system (FACTS) devices. The Y‐connection CMI is the most promising topology in application to adjustable speed drives and photovoltaic (PV) power systems. Magnetic‐less multilevel DC‐DC converters are another emerging applications of the multilevel concept, which can achieve a high voltage boost factor with compact size, high efficiency, and suitable for high temperature application. Multilevel converters involve a high fault possibility owing to the large number of components. This chapter also analyzes the fault tolerance and reliability of multilevel converters.
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paper_title: Dual-Multiphase Motor Drives for Fault-Tolerant Applications: Power Electronic Structures and Control Strategies

paper_content:

This paper analyzes two fault-tolerant dual-multiphase motor drives, a series-connected topology, and a standard H-bridge topology. Previous studies have shown that the series connected topology is appropriate to an aerospace application and has lower peak current in degraded mode in comparison with the H-bridge topology, which may consequently diminish the system's weight and cost. This paper extends the study to compare different control strategies of these structures under two fault conditions: short-circuit of an inverter's switch and an open-phase of the machine. The control strategies analyzed in this paper do not impact the fundamental current or the torque generation, but the amplitudes of some harmonics in degraded mode are expected to be narrowed down in order to reduce the inverter's size. Some analyses of maximum voltage and peak current in degraded mode have been used for inverter dimensioning. Experimental results are shown and compared to the simulated ones to confirm the validity of this study.
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paper_title: Vector control of fixed joint double fifteen-phase induction motors system with propeller load

paper_content:

Two fifteen-phase induction motors fixed on a single shaft is used in a ship propulsion system, and drive system of fixed joint motors with propeller load is studied in this paper. Fifteen-phase induction motor and propeller load are analyzed and modeled. Vector control system is designed, which can regulate the power allocation between two motors. Two working conditions of the ship are studied, and simulation results demonstrate that the two motors can work at equal or proportioned power respectively in four quadrants.
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paper_title: Integration of Six-Phase EV Drivetrains Into Battery Charging Process With Direct Grid Connection

paper_content:

The paper proposes two novel topologies for integrated battery charging of electric vehicles. The integration is functional and manifests through re-utilization of existing propulsion drivetrain components, primarily a six-phase inverter and a six-phase machine, to serve as components of a fast (three-phase) charging system. An important feature of the proposed charging systems is that they are with direct grid connection, thus nonisolated from the mains. Torque is not produced in machines during the charging process. The paper provides a comprehensive evaluation of the novel systems, together with an existing topology. Various aspects of the considered chargers are detailed and elaborated, including current balancing, interleaving modulation strategy, and influence of rotor field pulsation on control and overall performance. A control strategy is proposed and the theory and control scheme are verified by experiments.
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paper_title: Overview of Electric Motor Technologies Used for More Electric Aircraft (MEA)

paper_content:

This paper presents an overview of motor drive technologies used for safety-critical aerospace applications, with a particular focus placed on the choice of candidate machines and their drive topologies. Aircraft applications demand high reliability, high availability, and high power density while aiming to reduce weight, complexity, fuel consumption, operational costs, and environmental impact. New electric driven systems can meet these requirements and also provide significant technical and economic improvements over conventional mechanical, hydraulic, or pneumatic systems. Fault-tolerant motor drives can be achieved by partitioning and redundancy through the use of multichannel three-phase systems or multiple single-phase modules. Analytical methods are adopted to compare caged induction, reluctance, and PM motor technologies and their relative merits. The analysis suggests that the dual (or triple) three-phase PMAC motor drive may be a favored choice for general aerospace applications, striking a balance between necessary redundancy and undue complexity, while maintaining a balanced operation following a failure. The modular single-phase approach offers a good compromise between size and complexity but suffers from high total harmonic distortion of the supply and high torque ripple when faulted. For each specific aircraft application, a parametrical optimization of the suitable motor configuration is needed through a coupled electromagnetic and thermal analysis, and should be verified by finite-element analysis.
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paper_title: A Nine-Phase Permanent-Magnet Motor Drive System for an Ultrahigh-Speed Elevator

paper_content:

This paper presents a nine-phase permanent-magnet synchronous motor (PMSM) drive system based on multiple three-phase voltage source inverters. The nine-phase PMSM was developed as a traction motor for an ultrahigh-speed elevator. The mathematical model of the motor was simplified through symmetry of the system. Using the simplified model, the drive system can be controlled by the well-known d-q control theory. The feasibility and validity of the drive system were experimentally demonstrated at the world's tallest elevator test tower. Moreover, an additional experiment was performed to ensure the fault-tolerance capability of the system.
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paper_title: Series-Connected HV-IGBTs Using Active Voltage Balancing Control With Status Feedback Circuit

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Transient voltage unbalance is the major problem that limits the application of series-connected IGBTs in high-voltage and high-power converters. Asynchronous gate delay causes series-connected IGBTs not to turn-on and turn-off at the same time resulting in severely unbalanced voltage sharing. An active voltage balancing control technique is proposed in this paper to solve the asynchronous gate delay problem. By sampling the feedback signal caused by unbalanced voltage sharing, the microcontroller generates a time delay for the gate driver to compensate the asynchronous gate delay. The most vital part of active voltage balancing control, the status feedback circuit, is also discussed in detail in this paper. The function of the status feedback circuit and the effect of active voltage balancing control are verified in a two series-connected HV-IGBTs platform in rated operation (5 kV bus voltage and 600 A load current).
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paper_title: Multiphase Electric Machines for Variable-Speed Applications

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Although the concept of variable-speed drives, based on utilization of multiphase machines, dates back to the late 1960s, it was not until the mid- to late 1990s that multiphase drives became serious contenders for various applications. These include electric ship propulsion, locomotive traction, electric and hybrid electric vehicles, ldquomore-electricrdquo aircraft, and high-power industrial applications. As a consequence, there has been a substantial increase in the interest for such drive systems worldwide, resulting in a huge volume of work published during the last ten years. An attempt is made in this paper to provide a brief review of the current state of the art in the area. After addressing the reasons for potential use of multiphase rather than three-phase drives and the available approaches to multiphase machine designs, various control schemes are surveyed. This is followed by a discussion of the multiphase voltage source inverter control. Various possibilities for the use of additional degrees of freedom that exist in multiphase machines are further elaborated. Finally, multiphase machine applications in electric energy generation are addressed.
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paper_title: Mathematical Modeling of a 12-Phase Flux-Switching Permanent-Magnet Machine for Wind Power Generation

paper_content:

In this paper, a mathematical model of a 12-phase flux-switching permanent magnet (FSPM) machine designed for high-power wind power generation is established and investigated. First, the winding inductances in both the stator reference frame and the $dq$ -axes reference frame are analyzed. It should be noted that the characteristics of the 12-phase winding inductances are different from those of its three-phase counterpart. The largest mutual inductance is much smaller than half of the self-inductance, and most mutual inductances are negligible, which brings the benefit of improved magnetic isolation between phases and causes the 12th-order inductance matrix to be sparse. Thereafter, an accurate inductance model is established, taking account of the magnetic coupling between adjacent three-phase winding sets. Finally, a flux-linkage equation, a voltage equation, a power equation, and a torque equation are derived in sequence. The effectiveness of the proposed mathematical model is verified by comparing the theoretical results with 2-D finite-element-analysis-based predictions. The work in this paper lays an important foundation for the control strategy of the 12-phase FSPM machine.
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paper_title: Fault-Tolerant Operation of an Open-End Winding Five-Phase PMSM Drive With Short-Circuit Inverter Fault

paper_content:

Multiphase machines are well known for their fault-tolerant capability. Star-connected multiphase machines have fault tolerance in an open circuit. For an inverter switch short-circuit fault, it is possible to keep a smooth torque of a permanent magnet synchronous machine if the currents of the faulty phases are determined and their values are acceptable. This paper investigates fault-tolerant operations of an open-end five-phase drive, i.e., a multiphase machine fed with a dual-inverter supply. Inverter switch short-circuit fault is considered and handled with a simple solution. Original theoretical developments are presented. Simulation and experimental results validate the proposed strategy.
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paper_title: IGBT-Gating Failure Effect on a Fault-Tolerant Predictive Current-Controlled Five-Phase Induction Motor Drive

paper_content:

Multiphase machine drives are gaining importance in high-reliability applications due to their fault-tolerance capability and their ability to cope with the postfault operation without any extra electronic components. Predictive current controllers have been recently proposed for managing postfault operation of these drives when an open-phase fault is considered. However, the faulty situation assumes zero stator current while freewheeling diodes can continue conducting in a noncontrolled mode. This work analyzes the postfault operation of the five-phase drive when the freewheeling diodes of the faulty phase are still conducting. Experimental results are provided using a conventional insulated-gate bipolar transistor (IGBT)-based multiphase power converter to quantify the effect of the freewheeling diodes, when an IGBT-gating fault occurs, on the model-based predictive current-controlled drive.
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paper_title: Space vector PWM control of dual three phase induction machine using vector space decomposition

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The technique of vector space decomposition control of voltage source inverter fed dual three phase induction machines is presented in this paper. By vector space decomposition, the analysis and control of the machine are accomplished in three two-dimensional orthogonal subspaces and the dynamics of the electromechanical and nonelectromechanical energy conversion related machine variables are thereby totally decoupled. A space vector PWM technique is also developed based on the vector space decomposition to limit the fifth, and seventh harmonic currents which in such a system would be otherwise difficult to control. The techniques developed in this paper can be generalized for the control of an induction machine with an arbitrary number of phases.<<ETX>>
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paper_title: A Space Vector PWM With Common-Mode Voltage Elimination for Open-End Winding Five-Phase Drives With a Single DC Supply

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Open-end winding three-phase drive topologies have been extensively investigated in the last two decades. In the majority of cases supply of the inverters at the two sides of the winding is provided from isolated dc sources. Recently, studies related to multiphase open-end winding drives have also been conducted, using isolated dc sources at the two winding sides. This paper investigates for the first time a five-phase open-end winding configuration, which is obtained by connecting a two-level five-phase inverter at each side of the stator winding, with both inverters supplied from a common dc source. In such a configuration it is essential to eliminate the common-mode voltage (CMV) that is inevitably created by usual PWM techniques. Based on the vector space decomposition (VSD), the switching states that create zero CMV are identified and plotted. A space vector pattern with large redundancy of switching states is obtained. Suitable space vectors are then selected to realize the required voltage reference at the machine terminals with zero CMV. The large number of redundant states enables some freedom in the choice of switching states to impress these space vectors. Out of numerous possibilities, two particular switching sequences are chosen for further investigation. Both are implemented in an experimental setup, and the results are presented and discussed.
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paper_title: STUDY ON MATHEMATICAL MODEL OF 3-&12-PHASE SYNCHRONOUS GENERATORS WITH AC AND BRIDGE RECTIFIED DC OUTPUT

paper_content:

The structural characteristics of a 3-12-phase synchronous generator with simultaneous AC and bridge recti-fied DC output (the double winding synchronous generator) are introduced. With some approximate assumptions, the twelve-phase four Y-connected stator windings displaced by 15(DC windings) are replaced by a equivalent three-phase Y-connected winding; then by dealing with the electromagnetic coupling between two sets of windings, the parameter relations associated with the coupling are obtained. According to the results gotten above, the concise flux-linkage and voltage equations of a 3-12-phase double winding synchronous generator are acquired, then its d- and q-axis equivalent circuits are derived ,which provide a sound theoretical basis for the research on this kind of synchronous generators.
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paper_title: PWM Strategy With Minimum Harmonic Distortion for Dual Three-Phase Permanent-Magnet Synchronous Motor Drives Operating in the Overmodulation Region

paper_content:

This study presents a novel overmodulation strategy for a six-phase voltage source inverter (VSI)-fed dual three-phase permanent-magnet synchronous motor. The proposed strategy can achieve minimum harmonic injection in the overmodulation region. Four-vector space vector pulse width modulation (SVPWM) renders mathematic foundations for this given method. However, the classical four-vector SVPWM used in six-phase VSI has asymmetrical pulse width modulation waveform, which makes it difficult for hardware implementation. In this paper, the modulation algorithms in both linear and overmodulation regions have been unified and implemented with the double zero-sequence injection PWM strategy. This strategy is able to overcome the inherent shortcomings of the four-vector SVPWM, and it achieves smooth transitions from linear to overmodulation region. Simulation analysis and experimental results demonstrate the effectiveness and feasibility of the proposed strategy.
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paper_title: Resilient current control of five-phase induction motor under asymmetrical fault conditions

paper_content:

This paper presents the resilient current control of a five-phase induction motor under asymmetrical fault conditions. This kind of control scheme ensures that the five-phase induction motor operates continuously and steadily without additional hardware connections in case of loss of up to two phases, which is of importance to some specific applications where fault tolerance and high reliability are required. The five-phase induction motor proposed adopts the concentrated winding structure and makes use of the third harmonic currents to generate the nearly rectangular flux distribution in the air gap resulting in improvement of flux density and increase of output torque. Under asymmetrical fault conditions, the proper third harmonic currents are still superimposed on the fundamental currents of the five-phase induction motor with the remaining phases so as to maintain a nearly rectangular air-gap flux similar to the symmetrical conditions. Consequently, the five-phase induction motor can still produce improved flux density and increased output torque. Simulation analysis and experimental verifications on the resilient current control of the five-phase induction motor under the symmetrical and asymmetrical conditions are included in this paper.
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paper_title: Vector control of fixed joint double fifteen-phase induction motors system with propeller load

paper_content:

Two fifteen-phase induction motors fixed on a single shaft is used in a ship propulsion system, and drive system of fixed joint motors with propeller load is studied in this paper. Fifteen-phase induction motor and propeller load are analyzed and modeled. Vector control system is designed, which can regulate the power allocation between two motors. Two working conditions of the ship are studied, and simulation results demonstrate that the two motors can work at equal or proportioned power respectively in four quadrants.
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paper_title: Design of Five-Phase Modular Flux-Switching Permanent-Magnet Machines for High Reliability Applications

paper_content:

This paper proposes and designs a new five-phase modular flux-switching permanent-magnet (M-FSPM) machine for high reliability applications. The key is the new machine topology which incorporates the concept of fault-tolerant teeth (FTT) to provide the desired decoupling among phases. The electromagnetic performances of the newly designed M-FSPM machines having 18 and 19 rotor poles are quantitatively analyzed including the flux, back-EMF, cogging torque as well as unbalanced magnetic force (UMF). The results show that the proposed M-FSPM machine not only retains the merits of stator-PM machines and multiphase machines, but also offers lower cost and higher fault-tolerant capability. Especially, the 10/19-pole one incorporates the merits of symmetric back-EMF and reduced cogging torque, while suffers from UMF. Two experimental M-FSPM machines are designed and built for exemplification. Experimental results of the prototypes are given to confirm the validity of the proposed machines.
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paper_title: Remedial Strategies of T-NPC Three-Level Asymmetric Six-Phase PMSM Drives Based on SVM-DTC

paper_content:

In this paper, novel remedial direct torque control (DTC) schemes are proposed for open-circuit faults in T-type neutral-point-clamping (T-NPC) three-level asymmetric six-phase permanent-magnet synchronous motor (PMSM) drives. First, a simplified space vector modulation (SVM) is designed and applied for DTC-controlled asymmetric six-phase drive, in such a way that both good current harmonic performance and fast dynamic response are available. Based on the SVM-DTC scheme, a remedial strategy is proposed for the open-circuit faults in phase windings. The key is to derive the relationship between the stator fluxes and the stator voltages of all phases under faulty condition. Then, a derived perturbation term is compensated for normal voltage references, and the fault-tolerant scheme is, thus, implemented without changing control structure of normal condition. The remedial DTC schemes are also studied and proposed for open-switch faults in T-NPC six-phase drives. The modulation methods are redesigned for the faults in half-bridge switches and NPC switches. The experiments are carried out on a laboratory prototype to verify the validity and performance of the proposed fault-tolerant control schemes.
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paper_title: Modeling and control of a multi-phase induction machine with structural unbalance

paper_content:

The multiphase winding structure provides an induction machine with capabilities of starting and running even with one or more of its stator phases open-circuited. However, when operated with such a structurally unbalanced condition, the dynamic properties of the machine will change drastically from its balanced operation condition. For example, field-oriented control strategies developed for a balanced winding structure will no longer function properly and could lead to catastrophic consequences. In this paper, a unified approach to the modeling and field-oriented control of dual three phase induction machine with one phase open is presented. Using the concept of vector space decomposition, the proposed technique is established on the basis of the asymmetrical winding structure directly, and thus provides a precise, physically insightful tool to the modeling and control of induction machines with structural unbalance.
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paper_title: Global Fault-Tolerant Control Technique for Multiphase Permanent-Magnet Machines

paper_content:

In this paper, a global fault-tolerant control (FTC) technique is proposed for multiphase permanent-magnet (PM) machine drives. The goal of the proposed FTC is to find a general closed-form solution for healthy phase currents under steady-state postfault conditions. Healthy phase currents are found through an optimization problem to produce ripple-free output torque with minimum ohmic losses. A comprehensive FTC approach should be able to provide fault-tolerant currents for multiphase machines with any number of phases. In addition, it needs to find currents based on fault type (open-circuit/short-circuit), fault locations [phase(s) and/or line(s)], connection of stator windings, and even different control objectives. An important feature of the proposed method is its flexibility and simplicity in dealing with all possible fault conditions. The proposed method is a great tool to evaluate fault-tolerant capability of different drive systems in terms of maximum available ripple-free torque and copper losses. Due to its simplicity and flexibility, it is also well-suited for real-time implementation. A five-phase PM machine is used as an example to investigate the validity of the proposed solutions through finite-element analysis and experimental tests.
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paper_title: Calculation and Measurement of Parameters of A Multiphase Induction Motor

paper_content:

Analysis and calculation of motor parameters help to design and control of a multiphase motor.This paper presented the analysis and calculation of parameters of a multiphase induction motor.Taking into account the actual structure of stator and squirrel cage rotor,the motor parameters in phase coordinate were calculated using winding function method,based on which the mathematical model of n-phase p-pole-pair induction motor is built up.Motor parameters in different d-q planes,including magnetizing inductances,harmonic leakage inductances,rotor resistances and leakage inductances,were deduced.Taking a 9-phase induction motor as an example,the motor parameters were calculated by analytical method,FEA (finite element analysis) method and experimental measurement respectively.The agreement between analytical results and other results verifies the analytical expression of the multiphase motor parameters.
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paper_title: A Comparison of Carrier-Based and Space Vector PWM Techniques for Three-Level Five-Phase Voltage Source Inverters

paper_content:

Multilevel inverter supplied multiphase variable-speed drive systems have in recent times started attracting more attention, due to various advantages that they offer when compared to the standard three-phase two-level drives. For proper functioning of such systems good pulsewidth modulation (PWM) strategy is of crucial importance. Control complexity of multiphase multilevel inverters increases rapidly with an increase in the number of phases and the number of levels. This paper deals with a three-level neutral point clamped (NPC) inverter supplied five-phase induction motor drive and analyses five PWM strategies: three are carrier-based (CBPWM) and two are space vector based (SVPWM). The aim is to provide a detailed comparison and thus conclude on pros and cons of each solution, providing a guideline for the selection of the most appropriate PWM technique. Experimental results are provided for all analysed PWM methods. The comparison of the PWM techniques is given in terms of the voltage and current waveforms and spectra, as well as the total harmonic distortion (THD) in a whole linear modulation index range, which is used as the global figure of merit. Properties of the common mode voltage (CMV) are also investigated. Complexity of the algorithms, in terms of the computational time requirements and memory consumption, is addressed as well. It is shown that the performance of the PWM techniques is very similar and that one CBPWM and one SVPWM technique are characterised with identical performance. However, using the algorithm complexity as the main criterion, space vector techniques are more involved.
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paper_title: Analytical Determination of DC-Bus Utilization Limits in Multiphase VSI Supplied AC Drives

paper_content:

Two-level multiphase voltage source inverters (VSIs) are typically used as the supply for multiphase machines. Such machines are often with concentrated winding in which case, certain low-order stator current harmonics are injected to provide torque enhancement. Also, a multimotor drive system can be realized by connecting a number of multiphase machines in series, using phase transposition while supplying the whole system from a single multiphase VSI. In both situations, it is important to know the limits of the inverter operation in the linear modulation region. This paper develops a simple method that enables analytical determination of the boundaries of the linear modulation region for all multiphase inverters with a prime number of phases. The limits are independent of the actual pulse width modulation (PWM) method utilized, and are equally applicable to both carrier-based and space vector PWM techniques. Theoretical considerations are verified experimentally using the five-phase and seven-phase VSI rigs.
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paper_title: Analysis and Experimental Evaluation of Harmonic Leakage Inductance for Polyphase PM Machines Having Close Slot and Pole Combinations

paper_content:

For fractional-slot concentrated winding permanent-magnet (PM) machines having close slot (Q) and pole (p) combinations, harmonic leakage inductance could be several times higher than magnetizing inductance, resulting in a low power factor and a small characteristic current. This paper tends to extend the investigation of harmonic leakage inductance to polyphase PM machines, which have been receiving great attention in safety-critical applications. The impact of phase belt and winding layer on the winding distribution factor, which is usually neglected in previous work, has been investigated. The inductance index as well as a completed calculation flowchart has been introduced, in order to offer a full picture of harmonic leakage and its impact on winding inductance. Five-phase and six-phase schemes with different slot/pole combinations have been investigated as examples for odd and even phase number machines, respectively. Furthermore, several prototype machines, including three-phase 12-slot/10-pole and six-phase 24-slot/22-pole single-layer and double-layer machines, were fabricated, and experimental verification has been conducted.
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paper_title: Improved Reliability in Solid-State AC Drives by Means of Multiple Independent Phase Drive Units

paper_content:

Phase redundancy is a proposed technique for improving the reliability of large solid-state adjustable-frequency ac drives. Based on the more general concept of parallel redundancy, this new technique relies heavily on the inherent capability of a general n-phase ac motor to continue operation with (n -1) or less of its stator phases excited. Motor performance degradation which inevitably accompanies such operation is sensitive to a variety of system parameters including the number of stator phases and the type of excitation source. A thorough evaluation of (n - 1)-phase excitation performance characteristics of an n-phase squirrel-cage induction motor is presented in this paper. Under favorable conditions, a large percentage of the motor's balanced excitation rating can be retained during postfault conditions of steady-state (n -1)-phase excitation. The n-phase-drive units must be conservatively designed to withstand transient stresses associated with fault-induced transitions from balanced n-phase to (n-1)-phase excitation. Key analytical results have been experimentally verified by tests conducted on a 5-hp six-phase squirrel-cage induction motor. Results of this investigation support the basic soundness of the phase-redundancy concept.
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paper_title: Third Harmonic Current Restraining of Five-phase Permanent Magnet Synchronous Motor Based on Dual Synchronous Rotating Coordinates

paper_content:

A dual-plane vector scheme with an additional pair of harmonic current controllers was proposed to restrain harmonic currents caused by dead-time effect of voltage source inverter(VSI) and the dis-sinusoidal EMF of five-phase permanent magnet synchronous motor(FPMSM).The low-order harmonic voltage generated by dead-time effect was researched.Using extended symmetrical component transformation,the mathematic model under rotating coordinate of FPMSM was deduced.The third harmonic voltage would cause large magnitude of harmonic current for the low impedance of third harmonic sub-space,so an additional pair of harmonic current controllers was introduced to compensate them.The whole arithmetic is implemented in a single FPGA chip,experimental results demonstrate the proposed compensation method can effectively restrain harmonic current generated by dead-time effect of VSI and dis-sinusoidal EMF.
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paper_title: Steady state performance analysis of multi-phase induction motor with non-sinusoidal supply

paper_content:

Electromagnetic performance analysis is the very foundation for electric machine design optimization. Thus, the research on performance evaluation methods for multi-phase induction machines with non-sinusoidal supply is of great theoretical value and practical importance, as such process is much more complicated than traditional methods developed for three-phase induction machines. The fundamental and third harmonic equivalent circuits are employed as design tools for induction machines supplied by non-sinusoidal voltages with third harmonic injection. Considering that the air-gap flux density is asymmetrical, extended distributed magnetic circuit approach(EDMCA) is used to calculate the fundamental and third harmonic EMFs. The performance of the induction machine is finally determined by calculating quantities such as the fundamental and third harmonic currents in steady state through 3 layers of iterations. Particularly, the inner-layer iteration that calculates the air-gap magnetic flux and the middle-layer iteration that determines the magnetizing current is quite different from the traditional performance analysis approach for three-phase induction machines. The proposed method is applied to a prototype fifteen-phase induction machine with non-sinusoidal supply. Close agreement between the calculated and experimental results at various working conditions indicates the high accuracy of the proposed method.
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paper_title: Fault-Tolerant Control of NPC Three-Level Inverters-Fed Double-Stator-Winding PMSM Drives Based on Vector Space Decomposition

paper_content:

The purpose of this paper is to study and propose the fault-tolerant control schemes for neutral-point-clamped (NPC) three-level inverters-fed permanent magnet synchronous motor drive with double stator windings. Both open-phase faults and open-switch faults are considered. The proposed schemes maintain the advantages of vector space decomposition (VSD) control for multiple-stator-winding drives, where the torque of multiple windings is controlled as a whole. Different optimization goals such as minimum copper loss and minimum current amplitude variance are achieved in the proposed fault-tolerant control for open-phase faults. Moreover, the impacts of open-switch faults on voltage vectors of the drive are analyzed, and the VSD-based remedial schemes are proposed for symmetric operation under open-switch faults by adjusting the switching modulation strategies. The current harmonics and dc-link midpoint voltage deviation are suppressed well with the proposed schemes. Both simulation and experimental results are given to verify the validity of the proposed modulation strategies and control schemes under faulty conditions.
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paper_title: Nonsinusoidal Power Supply Analysis for Concentrated-Full-Pitch-Winding Multiphase Induction Motor

paper_content:

This paper investigates a nonsinusoidal po- wer supply technique for a multiphase motor with a concen- trated full-pitch winding. The technique focuses on how to select harmonics, how to determine the harmonics ratio, and the effects on the air-gap and yoke flux densities. Gen- erally, the third-harmonic current is utilized for the air-gap flux density optimization in a five-phase motor. However, the method has a negative effect on the yoke flux density, and the yoke iron width should be increased. Alterna- tively, this problem can be solved by providing more control freedom degrees of the motor with a phase number greater than five. A nine-phase motor is employed to achieve the air-gap and yoke flux density distribution optimization si- multaneously. Moreover, the performance of both motors is compared in the sinusoidal and nonsinusoidal power supply modes. The analysis of the torque density and the efficiency demonstrates that a nonsinusoidal power supply is more suitable for a heavy-load operation. Theoretically obtained results are verified by experiments.
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paper_title: Variable-Speed Five-Phase Induction Motor Drive Based on Predictive Torque Control

paper_content:

Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and a reduction in the total power per phase are required. Strategies derived from the conventional field-oriented control have been traditionally used in high-performance speed-control applications of multiphase drives. The well-known direct torque control (DTC) technique has been also applied in the multiphase case, but the achieved performance with a hysteresis-control-based approach is far from that obtainable with the three-phase drive, although the control structure is actually more complex. In this paper, a predictive-torque-control method is introduced as an alternative to the DTC technique for the high-performance variable-speed operation of multiphase drives. Simulation and experimental results are provided to illustrate the properties of the developed method.
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paper_title: Arbitrary Power Sharing Among Three-Phase Winding Sets of Multiphase Machines

paper_content:

The paper develops a technique for arbitrary power sharing among three-phase winding sets of a multiphase generator. Multiple d − q modeling is commonly used when independent control of the winding sets is required. This paper utilizes instead the vector space decomposition modeling as the starting point and combines it with a multiple d − q approach to preserve the advantages of the vector space decomposition, while still enabling independent control over each winding set. The power sharing is achieved by imposing appropriate x − y currents at the fundamental frequency so that the flux and average torque are not affected. The theory is developed initially for the nine-phase machine. A general expression for arbitrary current sharing is derived further for any multiphase machine with multiple three-phase windings. The obtained equations are valid for any possible machine topology (asymmetrical/symmetrical, with single or multiple neutral points). The theory is validated experimentally using an asymmetrical nine-phase induction generator with indirect rotor field oriented control.
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paper_title: Nonsinusoidal Power Supply Analysis for Concentrated-Full-Pitch-Winding Multiphase Induction Motor

paper_content:

This paper investigates a nonsinusoidal po- wer supply technique for a multiphase motor with a concen- trated full-pitch winding. The technique focuses on how to select harmonics, how to determine the harmonics ratio, and the effects on the air-gap and yoke flux densities. Gen- erally, the third-harmonic current is utilized for the air-gap flux density optimization in a five-phase motor. However, the method has a negative effect on the yoke flux density, and the yoke iron width should be increased. Alterna- tively, this problem can be solved by providing more control freedom degrees of the motor with a phase number greater than five. A nine-phase motor is employed to achieve the air-gap and yoke flux density distribution optimization si- multaneously. Moreover, the performance of both motors is compared in the sinusoidal and nonsinusoidal power supply modes. The analysis of the torque density and the efficiency demonstrates that a nonsinusoidal power supply is more suitable for a heavy-load operation. Theoretically obtained results are verified by experiments.
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paper_title: Determination of Harmonic Voltages for Fifteen-phase Induction Motors With Non-sinusoidal Supply

paper_content:

The 3-order harmonic injection voltage of a fifteen-phase induction motor with non-sinusoidal supply is determined,which provides theoretical basis for PWM of the supply voltage.With ideal operation criterion that the peak value of air-gap MMF is of the maximum descending amplitude established,the spatial location and magnitude relation between fundamental MMF and 3-order harmonic MMF are obtained.Based on the fundamental equivalent circuit and the 3-order harmonic equivalent circuit of the fifteen-phase induction motor,corresponding exciting currents are selected as references to calculate RMS values of the fundamental voltage and the 3-order harmonic voltage,which also yields the phase-angle difference between the negative wave crest of 3-order harmonic MMF and the positive wave crest of the fundamental MMF.The accuracy of the proposed method is verified by no-load experiment of the induction motor.Under the rated fundamental supply voltage,the fundamental exciting currents and the 3-order harmonic exciting currents at different given slips are computed,and then the RMS values of the 3-order harmonic voltages with phase-angle differences between MMF waves are obtained.Finally,the 3-order harmonic voltages at any slips are acquired by the linear interpolation.
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paper_title: Current Harmonics Compensation Based on Multiresonant Control in Synchronous Frames for Symmetrical $n$-Phase Machines

paper_content:

Low-order odd current harmonics arise in practical multiphase drives due to machine and converter nonlinear behavior (e.g., deadtime and flux saturation). If the windings are distributed, some harmonics cause torque ripple, whereas others produce losses. The latter is aggravated by the small impedance in the no-torque subspaces. Current harmonics can be compensated without steady-state error by proportional–integral controllers in multiple synchronous frames (SFs); however, a heavy computational load is required. In three-phase systems, the computational burden of this multiple SF (MSF) scheme is often avoided by implementing instead resonant controllers (RCs) tuned at the harmonics that are multiples of six in an SF rotating with the fundamental frequency. A similar structure has been proposed for nonlinearities compensation in asymmetrical six-phase machines. This paper extends this multiple RC (MRC) strategy to symmetrical machines of any phase number. The optimum frequencies for the RCs and for the SF in each plane, so that the number of RCs is minimized, are established. Then, the computational load of the resulting generic MRC scheme is assessed and compared with that of the MSF structure. The conditions in which the former is particularly preferable over the latter are identified. Experimental results are provided.
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paper_title: Current Balance Control for Symmetrical Multiphase Inverters

paper_content:

The current imbalance between stator phase windings could shorten the motor life and affect the drive performance, whereas in case of multiphase drive applications, there is not a general current balance control strategy that can apply to symmetrical inverters with any phase number m . Based on the generalized symmetrical component theory, this letter analyzed the values of relative symmetrical components of the multiphase systems in balanced and unbalanced cases. Then, developed from the conventional rotor-flux oriented control (RFOC), the current-balance RFOC is proposed to compensate the current imbalance for symmetrical m -phase inverters. Finally, the experimental results from the five-phase and nine-phase drive systems confirm the validity of the control strategy in eliminating current imbalance.
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paper_title: Series-Connected HV-IGBTs Using Active Voltage Balancing Control With Status Feedback Circuit

paper_content:

Transient voltage unbalance is the major problem that limits the application of series-connected IGBTs in high-voltage and high-power converters. Asynchronous gate delay causes series-connected IGBTs not to turn-on and turn-off at the same time resulting in severely unbalanced voltage sharing. An active voltage balancing control technique is proposed in this paper to solve the asynchronous gate delay problem. By sampling the feedback signal caused by unbalanced voltage sharing, the microcontroller generates a time delay for the gate driver to compensate the asynchronous gate delay. The most vital part of active voltage balancing control, the status feedback circuit, is also discussed in detail in this paper. The function of the status feedback circuit and the effect of active voltage balancing control are verified in a two series-connected HV-IGBTs platform in rated operation (5 kV bus voltage and 600 A load current).
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paper_title: Multiphase induction motor drives – a technology status review

paper_content:

The area of multiphase variable-speed motor drives in general and multiphase induction motor drives in particular has experienced a substantial growth since the beginning of this century. Research has been conducted worldwide and numerous interesting developments have been reported in the literature. An attempt is made to provide a detailed overview of the current state-of-the-art in this area. The elaborated aspects include advantages of multiphase induction machines, modelling of multiphase induction machines, basic vector control and direct torque control schemes and PWM control of multiphase voltage source inverters. The authors also provide a detailed survey of the control strategies for five-phase and asymmetrical six-phase induction motor drives, as well as an overview of the approaches to the design of fault tolerant strategies for post-fault drive operation, and a discussion of multiphase multi-motor drives with single inverter supply. Experimental results, collected from various multiphase induction motor drive laboratory rigs, are also included to facilitate the understanding of the drive operation.
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paper_title: Sensorless Direct Torque Control of Five-Phase Interior Permanent-Magnet Motor Drives

paper_content:

This paper presents the sensorless direct torque control (DTC) technique for five-phase interior permanent-magnet (IPM) motors. By using the introduced technique, fast torque response with low ripple in the stator flux and torque of the five-phase IPM can be achieved. Having 32 space voltage vectors provides a great flexibility in selecting the inverter switching states. Therefore, the stator flux and torque can be more precisely adjusted. Position information and speed are being estimated based on the position of the stator flux linkages. The mathematical model of the five-phase IPM motor is first derived. Later, the speed sensorless DTC method of the five-phase system is introduced. A five-phase IPM motor and a five-leg insulated-gate-bipolar-transistor-based inverter were designed and fabricated in the laboratory. The control method is implemented on a TMS320C32 digital signal processor board.
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paper_title: A novel direct torque control (DTC) method for five-phase induction machines

paper_content:

In this paper, a direct torque control (DTC) scheme of a five-phase induction motor is developed. A novel DTC scheme is proposed, where fast torque response with low ripple in the stator PM and torque of five-phase induction motor can be achieved. In comparison with DTC for three phase induction motor, the five-phase DTC system has thirty-two space voltage vectors, which provide greater flexibility in selecting the inverter switching states thus accomplishing a more precise control of the stator flux and torque. Simulation and experimental results clearly demonstrate a better dynamic and steady state performance with DTC for five-phase induction motor, which suggest that the combination of DTC with multi-phase induction motor have a great practical prospect in motor drives.
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paper_title: Variable-Speed Five-Phase Induction Motor Drive Based on Predictive Torque Control

paper_content:

Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and a reduction in the total power per phase are required. Strategies derived from the conventional field-oriented control have been traditionally used in high-performance speed-control applications of multiphase drives. The well-known direct torque control (DTC) technique has been also applied in the multiphase case, but the achieved performance with a hysteresis-control-based approach is far from that obtainable with the three-phase drive, although the control structure is actually more complex. In this paper, a predictive-torque-control method is introduced as an alternative to the DTC technique for the high-performance variable-speed operation of multiphase drives. Simulation and experimental results are provided to illustrate the properties of the developed method.
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paper_title: IGBT-Gating Failure Effect on a Fault-Tolerant Predictive Current-Controlled Five-Phase Induction Motor Drive

paper_content:

Multiphase machine drives are gaining importance in high-reliability applications due to their fault-tolerance capability and their ability to cope with the postfault operation without any extra electronic components. Predictive current controllers have been recently proposed for managing postfault operation of these drives when an open-phase fault is considered. However, the faulty situation assumes zero stator current while freewheeling diodes can continue conducting in a noncontrolled mode. This work analyzes the postfault operation of the five-phase drive when the freewheeling diodes of the faulty phase are still conducting. Experimental results are provided using a conventional insulated-gate bipolar transistor (IGBT)-based multiphase power converter to quantify the effect of the freewheeling diodes, when an IGBT-gating fault occurs, on the model-based predictive current-controlled drive.
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paper_title: Variable-Speed Five-Phase Induction Motor Drive Based on Predictive Torque Control

paper_content:

Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and a reduction in the total power per phase are required. Strategies derived from the conventional field-oriented control have been traditionally used in high-performance speed-control applications of multiphase drives. The well-known direct torque control (DTC) technique has been also applied in the multiphase case, but the achieved performance with a hysteresis-control-based approach is far from that obtainable with the three-phase drive, although the control structure is actually more complex. In this paper, a predictive-torque-control method is introduced as an alternative to the DTC technique for the high-performance variable-speed operation of multiphase drives. Simulation and experimental results are provided to illustrate the properties of the developed method.
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paper_title: Analysis and simulation of five-phase variable-speed induction motor drives under asymmetrical connections

paper_content:

In this paper, a dq model based on transformation theory for five-phase induction machines is presented. A detailed implementation of an indirect-type five-phase field-orientation control including the hysteresis-type pulsewidth modulation (PWM) current regulator is described. A method for continuous and disturbance-free operation of a five-phase field-oriented-controlled induction motor drive with complete loss of one, two, or even three legs of the inverter or motor phases is described. A complete analysis and computer simulation of this control technique is included.
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paper_title: Control of Multiphase Induction Motors With an Odd Number of Phases Under Open-Circuit Phase Faults

paper_content:

In this paper, a control scheme for multiphase induction motor drives is presented and assessed. This control scheme ensures the operation of a multiphase drive under an open-circuit phase fault that can occur in one or more phases at the same time. A fault-tolerant control strategy is developed. The mathematical analysis is based on the space vector representation of the multiphase system and is valid either in transient or steady-state operating conditions. The feasibility of the drive is verified by means of experimental tests carried out on a prototype of seven-phase induction motor.
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paper_title: Enhancing Fault-Tolerant Ability of a Nine-Phase Induction Motor Drive System Using Fuzzy Logic Current Controllers

paper_content:

With distinct advantages over three-phase machines, multiphase machines are gaining increasing popularity in ship electric propulsion applications. Many fault-tolerant control strategies have been proposed for multiphase drive to suppress the torque ripples under faulty conditions; however, most of them depend heavily on the mathematical models and the need of the prefault to postfault transitions, which would increase the complexity of the control system. Because of high robustness, Fuzzy Logic controllers are suggested to substitute the proportion integration (PI) controllers in the current loops of rotor-flux oriented control (RFOC) for multiphase induction motors in this paper. The experimental results from a multiphase drive platform demonstrate that compared with the conventional RFOC with PI current controllers, Fuzzy logic-RFOC has significantly improved the fault-tolerant ability of the nine-phase drive system in various kinds of faulty conditions.
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paper_title: Dual-Multiphase Motor Drives for Fault-Tolerant Applications: Power Electronic Structures and Control Strategies

paper_content:

This paper analyzes two fault-tolerant dual-multiphase motor drives, a series-connected topology, and a standard H-bridge topology. Previous studies have shown that the series connected topology is appropriate to an aerospace application and has lower peak current in degraded mode in comparison with the H-bridge topology, which may consequently diminish the system's weight and cost. This paper extends the study to compare different control strategies of these structures under two fault conditions: short-circuit of an inverter's switch and an open-phase of the machine. The control strategies analyzed in this paper do not impact the fundamental current or the torque generation, but the amplitudes of some harmonics in degraded mode are expected to be narrowed down in order to reduce the inverter's size. Some analyses of maximum voltage and peak current in degraded mode have been used for inverter dimensioning. Experimental results are shown and compared to the simulated ones to confirm the validity of this study.
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paper_title: Modeling and control of a multi-phase induction machine with structural unbalance

paper_content:

The multiphase winding structure provides an induction machine with capabilities of starting and running even with one or more of its stator phases open-circuited. However, when operated with such a structurally unbalanced condition, the dynamic properties of the machine will change drastically from its balanced operation condition. For example, field-oriented control strategies developed for a balanced winding structure will no longer function properly and could lead to catastrophic consequences. In this paper, a unified approach to the modeling and field-oriented control of dual three phase induction machine with one phase open is presented. Using the concept of vector space decomposition, the proposed technique is established on the basis of the asymmetrical winding structure directly, and thus provides a precise, physically insightful tool to the modeling and control of induction machines with structural unbalance.
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paper_title: Overview of Electric Motor Technologies Used for More Electric Aircraft (MEA)

paper_content:

This paper presents an overview of motor drive technologies used for safety-critical aerospace applications, with a particular focus placed on the choice of candidate machines and their drive topologies. Aircraft applications demand high reliability, high availability, and high power density while aiming to reduce weight, complexity, fuel consumption, operational costs, and environmental impact. New electric driven systems can meet these requirements and also provide significant technical and economic improvements over conventional mechanical, hydraulic, or pneumatic systems. Fault-tolerant motor drives can be achieved by partitioning and redundancy through the use of multichannel three-phase systems or multiple single-phase modules. Analytical methods are adopted to compare caged induction, reluctance, and PM motor technologies and their relative merits. The analysis suggests that the dual (or triple) three-phase PMAC motor drive may be a favored choice for general aerospace applications, striking a balance between necessary redundancy and undue complexity, while maintaining a balanced operation following a failure. The modular single-phase approach offers a good compromise between size and complexity but suffers from high total harmonic distortion of the supply and high torque ripple when faulted. For each specific aircraft application, a parametrical optimization of the suitable motor configuration is needed through a coupled electromagnetic and thermal analysis, and should be verified by finite-element analysis.
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paper_title: Remedial Field-Oriented Control of Five-Phase Fault-Tolerant Permanent-Magnet Motor by Using Reduced-Order Transformation Matrices

paper_content:

A five-phase fault-tolerant permanent-magnet (FTPM) motor can offer high torque density, low torque ripple, and good fault-tolerant capability. In order to improve operation performance under an open-circuit fault condition, this paper proposes a new remedial field-oriented control (RFOC) strategy for a five-phase FTPM motor. The novelty of the proposed RFOC strategy lies in the orthogonal reduced-order transformation matrix, which is derived from the fault-tolerant current references, and a new zero-sequence current related to torque ripple. The pulsation of the neutral voltage can be neglected in the RFOC strategy, having no effect on the control action. Also, the effect of the open-circuit fault on the motor drive model under the transformation matrix is discussed. A five-phase FTPM motor drive is prototyped and the proposed RFOC strategy is evaluated in terms of the steady-state and dynamic performances. The simulated and experimental results are given to verify the proposed strategy.
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paper_title: Controllability and Performance of a Nine-Phase FSPM Motor Under Severe Five Open-Phase Fault Conditions

paper_content:

Fault-tolerant controllability for a nine-phase flux-switching permanent magnet (NP-FSPM) machine under severe five open-phase fault is presented in this paper. First, combinations of additional degrees of freedom are derived to prove the high fault tolerance in the nine-phase drive system. Second, angles between the adjacent healthy phases are used to categorize the five open-phase fault cases, and stator-flux-oriented fault-tolerant control with harmonic current injection is developed to ensure the disturbance-free operation of the NP-FSPM machine drive. The main contribution is the investigation on the effect of the reconstructed harmonic current components on the machine phase currents and the dynamic performance under various switch transients. Also, some practical hints are given for implementation, such as the control degree of freedom, drive derating, and current control scheme. Experimental results are presented to validate the effectiveness of the sinusoidal current excitation and the high dynamic performance of the NP-FSPM machine drive system.
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paper_title: A Unified Fault-Tolerant Current Control Approach for Five-Phase PM Motors With Trapezoidal Back EMF Under Different Stator Winding Connections

paper_content:

A unified approach for fault-tolerant current control of five-phase permanent-magnet (PM) motors with trapezoidal back EMF is proposed for open-circuit phase and line faults. In addition to conventional star connection, five-phase PM motors can be connected in two penta-type connections, pentagon and pentacle. In the proposed unified approach, a general solution for fault-tolerant currents is presented which uses only the fundamental and third-harmonic current components for the excitation of the healthy stator phases. The proposed approach is based on mirror symmetry of healthy phase current with respect to the fault location and it is optimized to increase output average torque while reducing torque pulsations and minimizing ohmic losses. A general parametric solution is presented which can be applied to five-phase motor drives with any fault condition and winding connection by selecting proper optimization constraints. It is shown that penta-type connection results in improved fault-tolerant capability in terms of maximum ripple-free torque due to the absence of zero-neutral current constraint. Experimental results are presented to verify the proposed solutions for fault-tolerant current control.
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paper_title: Fault-Tolerant Control of NPC Three-Level Inverters-Fed Double-Stator-Winding PMSM Drives Based on Vector Space Decomposition

paper_content:

The purpose of this paper is to study and propose the fault-tolerant control schemes for neutral-point-clamped (NPC) three-level inverters-fed permanent magnet synchronous motor drive with double stator windings. Both open-phase faults and open-switch faults are considered. The proposed schemes maintain the advantages of vector space decomposition (VSD) control for multiple-stator-winding drives, where the torque of multiple windings is controlled as a whole. Different optimization goals such as minimum copper loss and minimum current amplitude variance are achieved in the proposed fault-tolerant control for open-phase faults. Moreover, the impacts of open-switch faults on voltage vectors of the drive are analyzed, and the VSD-based remedial schemes are proposed for symmetric operation under open-switch faults by adjusting the switching modulation strategies. The current harmonics and dc-link midpoint voltage deviation are suppressed well with the proposed schemes. Both simulation and experimental results are given to verify the validity of the proposed modulation strategies and control schemes under faulty conditions.
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paper_title: A Space Vector PWM With Common-Mode Voltage Elimination for Open-End Winding Five-Phase Drives With a Single DC Supply

paper_content:

Open-end winding three-phase drive topologies have been extensively investigated in the last two decades. In the majority of cases supply of the inverters at the two sides of the winding is provided from isolated dc sources. Recently, studies related to multiphase open-end winding drives have also been conducted, using isolated dc sources at the two winding sides. This paper investigates for the first time a five-phase open-end winding configuration, which is obtained by connecting a two-level five-phase inverter at each side of the stator winding, with both inverters supplied from a common dc source. In such a configuration it is essential to eliminate the common-mode voltage (CMV) that is inevitably created by usual PWM techniques. Based on the vector space decomposition (VSD), the switching states that create zero CMV are identified and plotted. A space vector pattern with large redundancy of switching states is obtained. Suitable space vectors are then selected to realize the required voltage reference at the machine terminals with zero CMV. The large number of redundant states enables some freedom in the choice of switching states to impress these space vectors. Out of numerous possibilities, two particular switching sequences are chosen for further investigation. Both are implemented in an experimental setup, and the results are presented and discussed.
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paper_title: Space Vector PWM Techniques for Three-to-Five-Phase Indirect Matrix Converter in the Overmodulation Region

paper_content:

In this paper, three overmodulation techniques for the three-to-five-phase indirect matrix converter (IMC) are proposed. The first technique utilizes only the adjacent large vectors in the sector in which the reference output voltage vector lies. The second technique improves on that by continuously adapting vector elimination in the $d_2{-}q_2$ vector space based on the output voltage requirements. The third technique utilizes the ripple in the dc link to further reduce the modulation index of the inverter stage during overmodulation. All three techniques increase the voltage transfer ratio of the three-to-five-phase IMC from 0.788 to 0.923, but with the addition of harmonics generated by a vector in the $d_2{-}q_2$ vector space of the inverter stage. Simulation and experimental results from a prototype three-to-five-phase IMC validate the three proposed overmodulation techniques.
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paper_title: The Development of a 20MW PWM Driver for Advanced Fifteen-Phase Propulsion Induction Motors

paper_content:

Since the power capacity needed for the propulsion of large ships is very large, a multiphase AC induction propulsion mode is generally adopted to meet the higher requirements of reliability, redundancy and maintainability. This paper gives a detailed description of the development of a 20MW fifteen-phase PWM driver for advanced fifteen-phase propulsion induction motors with a special third-harmonic injection in terms of the main circuit hardware, control system design, experiments, etc. The adoption of the modular design method for the main circuit hardware design can make the enclosed mechanical structure simple and maintainable. It can also avoid the larger switch stresses caused by the multiple turn on of the IGBTs in conventional large-capacity converter systems. The use of the distributed controller design method based on a high-speed fiber-optic ring net for the control system can overcome such disadvantages as the poor reliability and long maintenance times arising from the conventional centralized controller which is designed according to point-to-point communication. Finally, the performance of the 20MW PWM driver is verified by experimentation on a new fifteen-phase induction propulsion motor.
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paper_title: Configurations of high-power voltage source inverter drives

paper_content:

Synchronous machines fed by current source or cycloconverters have become standard solutions in high power applications. Mains side current shape and fundamental power factor are problems that arise using this type of drives. Therefore, recent developments tend to use induction machines fed by voltage source inverters (VSIs) also for high power drives. Inherent advantages are: a simple and less expensive induction motor which leads to an overall economic solution with a good power factor over the whole operation range. However, the switching and snubber losses of the gate turn-off thyristors (GTOs) limit the switching frequency to only a few hundred Hertz. This leads to severe drawbacks: high harmonics: low efficiency, and low maximum speed. In order to eliminate these drawbacks, the paper presents and compares improved solutions: combinations with series connected 2-level and 3-level VSIs and motors with 3 and 6 connections to the windings. >
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paper_title: Common-Mode Voltage Elimination in a Three-to-Five-Phase Dual Matrix Converter Feeding a Five-Phase Open-End Drive Using Space-Vector Modulation Technique

paper_content:

This paper proposes a space-vector modulation (SVM) algorithm for a five-phase open-end winding motor drive system, fed by a dual nonsquare matrix converter (MC). The input to each of the MCs (MC-1 and MC-2) is a three-phase utility grid, and the output is a five-phase with variable voltage, variable frequency capability. The major contribution of this paper is the elimination of the detrimental common-mode voltage (CMV) that appears across the motor winding. In addition, the proposed SVM allows for a unity power factor at the input side, while boosting the output phase voltage by up to 150% of input. This paper presents a comprehensive analysis, to obtain the expression for the SVM modulating signals that are used to generate the switching pulses for the MC. To verify the idea, a modular, reconfigurable 5-kW MC prototype, feeding a five-phase induction motor is built. The control algorithm is implemented on a dSPACE-1006 platform. The test shows that the CMV is successfully eliminated from the motor winding. Other results (i.e., current and voltage waveforms) are also found to be in very close agreement with the theoretical prediction and MATLAB simulation.
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paper_title: An Improved Space Vector Modulation for a Three-to-Seven-Phase Matrix Converter With Reduced Number of Switching Vectors

paper_content:

This paper proposes a space vector modulation (SVM) scheme for a three-to-seven-phase matrix converter (MC), feeding a variable-voltage variable-frequency multiphase drive. The main feature of the proposed technique is that it utilizes only 129 out of 2187 possible active space vectors for a successful ac–ac power conversion. Since the number of vectors is significantly reduced, the switching patterns are simplified, and the execution time of the algorithm is shortened. Despite the drastic reduction in the number of active vectors, it is found that there is no significant degradation in the performance of the MC. Furthermore, the SVM also produces balanced sinusoidal input currents with a unity power factor over a wide operational frequency range (1–110 Hz). In this paper, the theoretical analysis is supported by simulation and validated using a hardware prototype. The output voltage can reach up to 76.93% of the input voltage, which is the maximum physical limit of a three-to-seven-phase MC. In addition, it exhibits a better harmonic profile than the carrier-based modulation scheme; the total harmonic distortion for the output voltage waveform is measured to be below 5% over the entire operating frequency range.
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paper_title: An Open-End Winding Four-Level Five-Phase Drive

paper_content:

A four-level five-phase open-end winding (OeW) drive topology is introduced in this paper. The drive comprises a five-phase induction machine with open-end stator windings, supplied using two two-level voltage-source inverters with isolated and unequal dc-link voltages, in the ratio 2 : 1. The topology offers the advantages of a modular structure with fewer semiconductor components and has a greater potential for fault tolerance, as compared with an equivalent single-sided four-level drive. Due to the large number of switching states, development of a suitable space vector pulsewidth-modulation (PWM) method can be challenging. Hence, this paper examines the implementation of two-level-shifted carrier-based PWM methods. The effect of dead time on the drive performance is discussed, and it is shown that simultaneous PWM switching of both inverters can lead to degraded output phase voltage waveforms. Detailed analysis of this phenomenon is presented, a solution is proposed, and the modified modulation techniques are incorporated in an experimental setup, at first in conjunction with $V/f$ control. Once the proof of concept has been provided, full field-oriented control is implemented in this OeW drive topology for the first time; detailed experimental testing is conducted, and results are reported.
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paper_title: On the Causes of Circulating Currents in PWM Drives With Open-End Winding AC Machines

paper_content:

Electric drives with open-end winding ac machines offer certain advantages over drives with star- or delta-connected machines. Such drives have been recently considered for some applications such as electric vehicles. Circulating currents have been experimentally observed in such open-end winding ac drives. These currents have the effect of increasing conduction losses in the stator winding resistance of the ac machine. Two major causes for these currents have been identified as device voltage drops in power semiconductor devices and dead time used for shoot-through current protection. These effects are analyzed, and a mathematical description for predicting their severity is provided. Experimental results are presented that support the theory. The theory developed should be useful for devising solutions for this problem such as the design of common-mode filters. Two methods of suppressing the circulating currents are also outlined, and their experimental results are presented.
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paper_title: Analysis of common mode EMI for three-phase voltage source converters

paper_content:

A comprehensive analysis of common mode (CM) EMI is conducted for three-phase voltage source converters in various configurations. The analysis is based on the common mode equivalent circuit models derived from the detailed circuit models. Both frequency domain and time domain studies are performed for (a) three-phase PFC rectifier; (b) back-to-back connected rectifier and inverter; and (c) multiple back-to-back connected rectifiers/inverters with interleaved gating control. Contributions of the common mode voltage sources and coupling paths, as well as effect of a long cable and the common mode choke, are analyzed for both input-side and output-side conducted CM EMI. The analysis results give insights into the CM current generation, coupling, and mitigation methods for high power applications such as high performance double-conversion UPS, drives, microturbine generators, and doubly fed wind turbine-generators. Reduction of conducted CM current also mitigates the risk of radiated EMI issue for systems with long input or output cables.
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paper_title: Fault-Tolerant Interior-Permanent-Magnet Machines for Hybrid Electric Vehicle Applications

paper_content:

Multiphase interior permanent magnet (IPM) motors are very good candidates for hybrid electric vehicle applications. High torque pulsation is the major disadvantage of most IPM motor configurations. A five-phase IPM motor with low torque pulsation is discussed. The mathematical model of the five-phase motor is given. A control strategy that provides fault tolerance to five-phase permanent-magnet motors is introduced. In this scheme, the five-phase system continues operating safely under loss of up to two phases without any additional hardware connections. This feature is very important in traction and propulsion applications where high reliability is of major importance. The system that is introduced in this paper will guarantee high efficiency, high performance, and high reliability, which are required for automotive applications A prototype four-pole IPM motor with 15 stator slots has been built and is used for experimental verification.
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paper_title: Extending speed range of five-phase PM machines by changing the stator windings connections

paper_content:

Multi-phase permanent magnet machines are good candidate for electric vehicle (EV) and hybrid electric vehicle (HEV) applications due to their fault tolerance capability, high torque to current ratio, high efficiency and fast dynamic response. However limited speed range is a major drawback for these electric machines. Stator winding configuration has a significant effect in speed range operation of AC electric machines. In a three phase AC machine a wide speed range operation can be achieved by changing the stator winding connection from wye to delta. In this paper the performance of a five-phase permanent magnet machine with different winding configurations for the stator is investigated. Simulation results are carried out to show the performance of each stator winding connections over a wide speed range.
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paper_title: Enhancement of Steady-State Performance in Direct-Torque-Controlled Dual Three-Phase Permanent-Magnet Synchronous Machine Drives With Modified Switching Table

paper_content:

This paper investigates the improved switching-table-based direct torque control strategies (ST-DTC) for dual three-phase permanent magnet synchronous machine drives. The classical ST-DTC scheme for dual three-phase drives is usually seriously penalized by significant current harmonics, which cause large losses and reduce the efficiency of the drive system. Hence, a modified switching table consisting of 12 new synthetic voltage vectors is proposed. With this new switching table, not only the variables relating to the torque production are well controlled, but also the variables contributing to the current harmonics are eliminated successfully within one sampling period. Furthermore, a simple modified torque regulator is proposed to reduce the torque ripple and the steady-state error of torque which is usually observed in the real-time system. The switching sequence which is most suitable for the implementation of the real-time system has been proposed to minimize the computation burden. The proposed strategy only changes the switching table and torque regulator without any major modifications, and hence, the merits of the classical direct torque control, i.e., simple structure and good robustness, are still preserved. The experimental results validate the effectiveness of the proposed strategy.
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paper_title: Source of induction motor bearing currents caused by PWM inverters

paper_content:

The recent increase of bearing damage in induction machines driven by transistorized inverters has spurred activity on possible causes related to PWM inverters. This paper looks into a typical power conversion system from this perspective. It identifies the existence of the common mode voltages produced in all types of converters. A hypothesis is then proposed to explain the bearing current problem. In particular, it is shown that in an inverter-motor system the common mode voltages generated by a PWM inverter, which are attributed to PWM switching harmonics, couple through parasitic capacitances from stator windings to the rotor body and then returns through the motor bearings to the commonly grounded stator case as a closed loop circuit. The hypothesis is verified by experimental measurement of common mode coupling currents and true bearing currents in a specially modified induction motor. Solutions are then provided to suppress the bearing currents.
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paper_title: Space vector PWM control of dual three phase induction machine using vector space decomposition

paper_content:

The technique of vector space decomposition control of voltage source inverter fed dual three phase induction machines is presented in this paper. By vector space decomposition, the analysis and control of the machine are accomplished in three two-dimensional orthogonal subspaces and the dynamics of the electromechanical and nonelectromechanical energy conversion related machine variables are thereby totally decoupled. A space vector PWM technique is also developed based on the vector space decomposition to limit the fifth, and seventh harmonic currents which in such a system would be otherwise difficult to control. The techniques developed in this paper can be generalized for the control of an induction machine with an arbitrary number of phases.<<ETX>>
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paper_title: A Space Vector PWM With Common-Mode Voltage Elimination for Open-End Winding Five-Phase Drives With a Single DC Supply

paper_content:

Open-end winding three-phase drive topologies have been extensively investigated in the last two decades. In the majority of cases supply of the inverters at the two sides of the winding is provided from isolated dc sources. Recently, studies related to multiphase open-end winding drives have also been conducted, using isolated dc sources at the two winding sides. This paper investigates for the first time a five-phase open-end winding configuration, which is obtained by connecting a two-level five-phase inverter at each side of the stator winding, with both inverters supplied from a common dc source. In such a configuration it is essential to eliminate the common-mode voltage (CMV) that is inevitably created by usual PWM techniques. Based on the vector space decomposition (VSD), the switching states that create zero CMV are identified and plotted. A space vector pattern with large redundancy of switching states is obtained. Suitable space vectors are then selected to realize the required voltage reference at the machine terminals with zero CMV. The large number of redundant states enables some freedom in the choice of switching states to impress these space vectors. Out of numerous possibilities, two particular switching sequences are chosen for further investigation. Both are implemented in an experimental setup, and the results are presented and discussed.
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paper_title: Space Vector PWM Techniques for Sinusoidal Output Voltage Generation with a Five-Phase Voltage Source Inverter

paper_content:

Five-phase variable-speed drives currently are considered for numerous applications, including electric and hybrid-electric vehicles, traction, and ship propulsion. If the machine is designed with a concentrated stator winding, the third stator current harmonic injection can be used to enhance the torque production and the machine needs to be supplied with the fundamental and the third harmonic of the voltage. On the other hand, if the machine is with a sinusoidally distributed winding, the supply should consist of the fundamental harmonic only. Since five-phase drives are invariably supplied from five-phase voltage source inverters (VSIs), adequate methods for VSI pulse width modulation (PWM) are required. This article analyzes different space vector PWM (SVPWM) schemes for a five-phase VSI, which can be used for five-phase motor drives with sinusoidal distribution of windings. A detailed model of a five-phase VSI is presented first in terms of space vectors and the existing technique of utilizing only l...
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paper_title: STUDY ON MATHEMATICAL MODEL OF 3-&12-PHASE SYNCHRONOUS GENERATORS WITH AC AND BRIDGE RECTIFIED DC OUTPUT

paper_content:

The structural characteristics of a 3-12-phase synchronous generator with simultaneous AC and bridge recti-fied DC output (the double winding synchronous generator) are introduced. With some approximate assumptions, the twelve-phase four Y-connected stator windings displaced by 15(DC windings) are replaced by a equivalent three-phase Y-connected winding; then by dealing with the electromagnetic coupling between two sets of windings, the parameter relations associated with the coupling are obtained. According to the results gotten above, the concise flux-linkage and voltage equations of a 3-12-phase double winding synchronous generator are acquired, then its d- and q-axis equivalent circuits are derived ,which provide a sound theoretical basis for the research on this kind of synchronous generators.
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paper_title: A Vector Space Decomposition Based Space Vector PWM Algorithm for a Three-Level Seven-Phase Voltage Source Inverter

paper_content:

This paper presents a novel modulation strategy for a seven-phase three-level inverter, aimed at variable-speed drive applications. Developed space vector pulsewidth modulation (SVPWM) strategy is based on vector space decomposition (VSD) approach and an analysis of multidimensional space vector projections in mutually orthogonal planes. The algorithm represents an extension of a recently developed five-phase three-level SVPWM algorithm and is considerably more complex, due to the existence of three mutually orthogonal planes in a seven-phase system. The difficulties of generalization of space vector strategies, which stem from the nature of the multiphase systems, are highlighted. Increasing the number of phases from five to seven increases the number of switching states from 35 = 243 to 37 = 2187 and the number of orthogonal planes from two to three. This considerably affects the complexity of the offline calculations. However, the final implementation of the algorithm is simple. Developed SVPWM algorithm is compared to an equivalent carrier-based strategy and it is shown that they yield identical performance. The complexity of the algorithms for real-time implementation is compared. Simulation and experimental results, obtained using neutral-point clamped inverter, verify the theoretical developments.
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paper_title: Analysis of multiphase space vector pulse width modulation based on multiple d-q spaces concept

paper_content:

Multiphase motors are usually designed to have the concentrated winding and nonsinusoidal air gap flux density distribution in order to maximize the torque per ampere. This means that the phase voltage of a multiphase motor has the nonsinusoidal waveform. Accordingly, the conventional analysis on a multiphase space vector pulse width modulation (SVPWM), which is confined to a sinusoidal phase voltage, should be extended to a nonsinusoidal phase voltage. In this paper, based on a multiple d-q spaces concept a novel analysis on a multiphase SVPWM to synthesize an arbitrary nonsinusoidal phase voltage is proposed. Through out this paper, a five-phase inverter is used as a practical example. The basic concepts can be easily extended to an n-phase inverter.
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paper_title: Non-sinusoidal output voltage for multiphase variable speed drives with space vector PWM

paper_content:

Due to the low DC voltage utilization and small output torque of the multiphase induction motors with sinusoidal output voltage,the non-sinusoidal space vector pulse width modulation (PWM),NSVPWM,is modeled and the inter connection between NSVPWM and harmonic injection PWM is analyzed.The way how to decide the reference voltage vectors on d-q planes is introduced.A nine-phase concentrated winding induction machine is used as a practical example.By maintaining the amplitudes of the tooth flux density and yoke flux density as well as the stator copper loss,the output torques under three control strategies are compared.The experiment results show that the output torque of the ninephase concentrated winding induction machine with NSVPWM is over 6.42% than that with SPWM,and the reasons are given.
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paper_title: A Comparison of Carrier-Based and Space Vector PWM Techniques for Three-Level Five-Phase Voltage Source Inverters

paper_content:

Multilevel inverter supplied multiphase variable-speed drive systems have in recent times started attracting more attention, due to various advantages that they offer when compared to the standard three-phase two-level drives. For proper functioning of such systems good pulsewidth modulation (PWM) strategy is of crucial importance. Control complexity of multiphase multilevel inverters increases rapidly with an increase in the number of phases and the number of levels. This paper deals with a three-level neutral point clamped (NPC) inverter supplied five-phase induction motor drive and analyses five PWM strategies: three are carrier-based (CBPWM) and two are space vector based (SVPWM). The aim is to provide a detailed comparison and thus conclude on pros and cons of each solution, providing a guideline for the selection of the most appropriate PWM technique. Experimental results are provided for all analysed PWM methods. The comparison of the PWM techniques is given in terms of the voltage and current waveforms and spectra, as well as the total harmonic distortion (THD) in a whole linear modulation index range, which is used as the global figure of merit. Properties of the common mode voltage (CMV) are also investigated. Complexity of the algorithms, in terms of the computational time requirements and memory consumption, is addressed as well. It is shown that the performance of the PWM techniques is very similar and that one CBPWM and one SVPWM technique are characterised with identical performance. However, using the algorithm complexity as the main criterion, space vector techniques are more involved.
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paper_title: Development of a Three-to-Five-Phase Indirect Matrix Converter With Carrier-Based PWM Based on Space-Vector Modulation Analysis

paper_content:

This paper proposes an indirect matrix converter (IMC) topology to supply a five-phase load directly from three-phase ac power sources without bulky electrolytic capacitors and explains its operating principle. Using the emerging topology, which combines the five-leg inverter into the rectifier stage of the conventional IMC, the three-to-five-phase IMC topology reduces the number of power switches and results in a simpler commutation compared with the conventional three-to-five-phase direct matrix converter. In addition, a simple approach to realize the carrier-based pulsewidth modulation (CBPWM) method for a three-to-five-phase IMC is presented, and the proposed CBPWM method is analyzed based on the space-vector approach. As a result, the IMC with the proposed CBPWM method can be more easily implemented compared with IMCs with the space-vector PWM method. A three-to-five-phase IMC control platform is realized by coordinating a TMS320F28335 DSP (Texas Instruments) with an EPM7128SLC84-15 field-programmable gate array (Altera). The simulation and experimental results are provided to verify the effectiveness of the CBPWM strategy.
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paper_title: A Comparison of Carrier-Based and Space Vector PWM Techniques for Three-Level Five-Phase Voltage Source Inverters

paper_content:

Multilevel inverter supplied multiphase variable-speed drive systems have in recent times started attracting more attention, due to various advantages that they offer when compared to the standard three-phase two-level drives. For proper functioning of such systems good pulsewidth modulation (PWM) strategy is of crucial importance. Control complexity of multiphase multilevel inverters increases rapidly with an increase in the number of phases and the number of levels. This paper deals with a three-level neutral point clamped (NPC) inverter supplied five-phase induction motor drive and analyses five PWM strategies: three are carrier-based (CBPWM) and two are space vector based (SVPWM). The aim is to provide a detailed comparison and thus conclude on pros and cons of each solution, providing a guideline for the selection of the most appropriate PWM technique. Experimental results are provided for all analysed PWM methods. The comparison of the PWM techniques is given in terms of the voltage and current waveforms and spectra, as well as the total harmonic distortion (THD) in a whole linear modulation index range, which is used as the global figure of merit. Properties of the common mode voltage (CMV) are also investigated. Complexity of the algorithms, in terms of the computational time requirements and memory consumption, is addressed as well. It is shown that the performance of the PWM techniques is very similar and that one CBPWM and one SVPWM technique are characterised with identical performance. However, using the algorithm complexity as the main criterion, space vector techniques are more involved.
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paper_title: Reduction of Common-Mode Voltage in Multiphase Two-Level Inverters Using SPWM With Phase-Shifted Carriers

paper_content:

The increasing interest in multiphase drive systems has led to the extension of inverter topologies and pulse width modulation (PWM) methods from three-phase to multiphase occasions. Carrier-based PWM (CPWM) dominates space vector PWM when the phase number increases, because of its simple computation and modular implementation. Although intensive work has been done on modifying PWM methods to reduce the common-mode voltage (CMV), not enough work has been done on CPWM methods with CMV reduction for multiphase drives. This paper extends the phase-shifted sinusoidal PWM (PS-SPWM) method for five-phase and six-phase two-level voltage-source inverters (VSI) and employs the intersection-plotting method and Fourier analysis to reveal the nature of the CMV. Both experiment and simulation results comply with theoretical analysis that compared with the conventional SPWM, the PS-SPWM can effectively reduce the CMV in peak-to-peak value and RMS value, though it leads to a higher phase current distortion. In addition, the hardware realization of PS-SPWM for multiphase inverters by a distributed control system is presented in this paper.
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paper_title: Comprehensive Relationship Between Carrier-Based PWM and Space Vector PWM in a Five-Phase VSI

paper_content:

Multiphase machines are nowadays considered for high-power variable-speed drive applications due to numerous advantages that they offer when compared to their three-phase counterparts. Multiphase voltage source inverters are invariably used to provide multiphase variable voltage and variable frequency supply with appropriate pulsewidth modulation (PWM) control. Carrier-based PWM and space vector PWM (SVPWM) are the most common options. This paper is aimed at providing a comprehensive relationship between carrier-based PWM and SVPWM techniques. The relationship is determined in terms of modulation signals and space vectors, modulation signals and space vector sectors, and switching pattern of space vector and type of carrier. Distribution of zero vector is discussed, leading to different types of modulation schemes. The practical implementation issues of carrier-based PWM and SVPWM are discussed. Simulation results and their experimental validation are provided to support the analytical findings.
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paper_title: Simple Carrier-Based PWM Technique for a Three-to-Nine-Phase Direct AC–AC Converter

paper_content:

Multiphase (more than three phases) power electronic converters are required mainly for feeding variable-speed multiphase drive systems. This paper presents one such solution by using a direct ac-ac converter that can be used to supply a nine-phase drive system. The input is a fixed-voltage and fixed-frequency three-phase input, and the output is a variable-voltage and variable-frequency nine-phase output. A simple pulsewidth-modulation technique is developed for the proposed ac-ac converter named as a nonsquare three-to-nine-phase matrix-converter configuration. The developed modulation technique is based on the comparison of a high-frequency carrier signal with the duty ratios. Although the carrier-based scheme is widely employed for the control of back-to-back converters, it has recently been used for controlling a three-to-three-phase matrix converter. This concept is extended in this paper for controlling a three-to-nine-phase matrix converter. With the two techniques that are proposed, one outputs 0.75 of the input magnitude and the other outputs reach 0.762 of the input. This is the maximum value of the output voltage in the linear modulation range that can be achieved in this configuration of the matrix converter. The viability of the proposed control techniques is proved analytically through simulation and an experimental approach.
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paper_title: A Carrier-Based PWM Modulation Technique for Balanced and Unbalanced Reference Voltages in Multiphase Voltage-Source Inverters

paper_content:

The advancement in power electronics has made the use of any number of phases in ac machines possible since with the inverter, any number of phase voltages can be realized as long as the corresponding inverter exists. To supply multiphase drives requires multiphase voltage source inverters (VSIs) whose output voltages depend very much on the methods of generating the pulses to turn on and turn off the inverter devices appropriately. This paper presents an analytical technique for the determination of the expressions for the modulation signals used in the carrier-based sinusoidal and generalized discontinuous pulse width modulation schemes for two-level, five-phase voltage source converters. These expressions can be used for both balanced and unbalanced phase voltages generated by any two-level multiphase inverter, in generating the required reference signals appropriately. An example of a five-phase VSI is presented to illustrate the strategy. Simulation and experimental results are presented in which a close examination shows that both results are similar for the balanced and unbalanced load voltage cases.
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paper_title: Carrier-Based Pulse Width Modulation for Symmetrical Six-Phase Drives

paper_content:

Modulating the output of a voltage source inverter (VSI) inherently causes current distortions on the load side due to the switching behavior of the inverter. This paper describes a method to reduce these distortions for a drive setup with six phases. The setup consists of a six-phase machine connected to two three-leg two-level VSIs. The phases within the machine are symmetrically arranged and spatially shifted by $60^\circ$ . The phases are grouped so that two conventional three-phase sets are formed, each fed by one inverter. The output of each inverter leg is modulated by comparing a triangle carrier waveform with the desired fundamental wave. Arranged in this way, the drive setup offers an additional degree of freedom, the phase shift of the two carrier waveforms. It is shown that, depending on the machine parameters, there exists an optimal angle, which reduces the harmonic losses of the drive for a certain amplitude of the fundamental wave. The resulting overall current distortion can even be lower compared to a conventional three-phase drive with a two- or three-level inverter topology. For three different modulation techniques, the optimal phase shift angles are derived in an exact form, naturally, symmetrical regular and asymmetrical regular sampled pulse width modulation. An approximation with reasonable accuracy is achieved out of the exact solution. Simulations and experimental tests validate the theoretical considerations.
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paper_title: Investigation of Carrier-Based PWM Techniques for a Five-Phase Open-End Winding Drive Topology

paper_content:

This paper discusses the implementation of level-shifted and phase-shifted carrier-based modulation methods, in conjunction with a multiphase open-end winding drive topology. The considered drive is supplied using two five-phase two-level voltage source inverters (VSIs), with input provided from two isolated supplies of equal dc voltages. The topology is known to yield the same space-vector pattern as a corresponding three-level inverter in single-sided supply mode. It is shown in this paper that, with the application of a simple logic, the same phase voltage waveforms result as those obtainable with the appropriate carrier-based modulation scheme applied to the three-level VSI in single-sided supply mode. While the outcomes of the modulation techniques are the same, the open-end winding topology offers certain advantages, such as modularity and absence of capacitor voltage balancing requirements. The analysis is conducted for selected modulation methods using voltage and current waveforms, spectra Fast Fourier Transform (FFT), and total harmonic distortion as figures of merit. Theoretical considerations are verified by means of simulation and experimental results.
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paper_title: A Sawtooth Carrier-Based PWM for Asymmetrical Six-Phase Inverters With Improved Common-Mode Voltage Performance

paper_content:

A sawtooth carrier-based sinusoidal pulse width modulation (SC-SPWM) technique for asymmetrical six-phase two-level inverters is proposed in this paper, which could reduce both the peak-to-peak amplitude and the changing frequency of the common-mode voltage (CMV). The intersection-plotting method reveals that the mirror symmetrical sawtooth carriers for two three-phase groups can help optimize the distribution of overlapping areas, which is the CMV reduction mechanism of SC-SPWM. Additionally, the Fourier analysis is employed to quantitatively evaluate the modulation index and harmonic performance of SC-SPWM compared with the conventional SPWM and two phase-shifted SPWM methods. Also, further analysis demonstrates that dead time does not affect the reduction of CMV in a noticeable way. Finally, both simulation and experimental results coincide with the theoretical analysis that the proposed SC-SPWM shows the best performance in reducing the CMV amplitude and changing frequency among these four SPWM methods, though it leads to a higher phase current distortion.
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Title: A Review of Drive Techniques for Multiphase Machines

Section 1: INTRODUCTION
Description 1: Introduce the context of multiphase machines, highlighting their advantages and increasing popularity in industrial applications.

Section 2: HISTORY OF MULTIPHASE DRIVE
Description 2: Provide a historical overview of the development and research on multiphase drive systems, mentioning key milestones and contributors.

Section 3: MULTIPHASE MOTOR DRIVE CONTROL
Description 3: Discuss the principles and techniques used in the control of multiphase motors, including the various sophisticated algorithms employed.

Section 4: FAULT-TOLERANT CONTROL
Description 4: Address the fault-tolerant capabilities of multiphase machines and the strategies used to handle different kinds of faults in drive systems.

Section 5: TOPOLOGY OF MULTIPHASE CONVERTERS
Description 5: Review different multiphase converter topologies, categorizing them based on power conversion processes and neutral point connections.

Section 6: PWM TECHNIQUES FOR MULTIPHASE INVERTERS
Description 6: Explore the various PWM (Pulse Width Modulation) techniques used for multiphase inverters, focusing on SVPWM and CPWM methods.

Section 7: CONCLUSIONS
Description 7: Summarize the review findings and provide predictions regarding the future trends and advancements in multiphase drive and control techniques.