Power Switch Faults, Diagnosis and Tolerant Schemes in Converters of Photovoltaic Systems- A Review
---
paper_title: Robustness evaluation of high voltage Press Pack IGBT modules in enhanced short circuit test

paper_content:

The paper deals with the evaluation of robustness of high power Press Pack IGBT modules under short circuit conditions. The severity of the tests is usually related to the achievement of the real failure mode which drives the device to withstand a big amount of energy. The most and well known methods to evaluate the robustness of the devices have been analyzed and improved in order to operate with the highest achievable di/dt and to consequently emulate the real circuit setup and failure mode. Experimental tests will be shown and evaluated under different voltage and temperature conditions. The tests described in the paper have been targeted to evaluate the capability of the device to withstand extremely severe condition when they are used in a high power converter. A driving protection feature dealing with the target of improving the functionality of protection against failure will be also described.
---
paper_title: Reliability of power cycling for IGBT power semiconductor modules

paper_content:

Power cycling capability is one of the most important reliability items in application semiconductor modules. This paper describes the mechanism of power cycling by analysis of the structure of lead-based solder and joint failure due to fatigue was studied to ascertain improvement in the power cycling lifetime. Lead-based solder has a relatively weaker yield-strength which means that plastic deformation leads to deterioration. Therefore, tin-silver based solder was selected as a higher yield-strength material, and a new composition which has both excellent mechanical properties and wettability was developed. Concerning the failure mechanism of power cycling for this newly developed solder material, solder joint failure and aluminum wire bond failure were clearly distinguished, and the lifetime prediction curve was clarified by FEM analysis and detailed failure analysis. Furthermore, it was proved that the deterioration of new tin-silver based solder is caused by thermal fatigue with the grain growth of tin. Thus, longer power cycling capability is achieved by using this newly developed solder instead of conventional lead-based solder.
---
paper_title: Ageing and Failure Modes of IGBT Modules in High-Temperature Power Cycling

paper_content:

This paper presents an experimental study on the ageing of insulated-gate bipolar transistor (IGBT) power modules. The aim is to identify the effects of power cycling on these devices with high baseplate temperatures (60 °C to 90 °C) and wide temperature swings (60 °C to 100 °C). These values for thermal stresses have been defined according to automotive applications. The test conditions are provided by two types of test benches that will be described in this paper. The changes in electrical and thermal indicators are observed regularly by a monitoring system. At the end of the test (reaching damage criterion or failure), different analyses are performed (acoustic scanning and SEM imaging), and the damage is listed systematically. Nineteen samples of 600-V 200-A IGBT modules were thus aged using five different power-cycling protocols. The final summary of results shows that ageing mechanisms mainly concern wire bonds and emitter metallization, with gradual impact depending on protocol severity.
---
paper_title: THERMAL FATIGUE AND FAILURE OF ELECTRONIC POWER DEVICE SUBSTRATES.

paper_content:

Abstract Electronic power devices used for transportation applications (automotive and avionics) experience severe temperature variations, which promote their thermal fatigue and failure. For example, for power modules mounted on the engine of an aircraft, temperature variations range from −55 °C (in the worst case of storage before takeoff) to +200 °C (flight). Direct bonded copper (DBC) substrates are used to isolate chips (silicon dies) from their base plates. For large thermal amplitudes, the failure occurs in DBC substrates, which are copper/ceramic/copper sandwiches. The Weibull approach was used to model the brittle fracture of the ceramic layer from a natural defect. Furthermore, geometric singularities in the upper ceramic/copper interface are at the origin of cracks that grow by fatigue along the interface and finally bifurcate and break the ceramic layer. It is discussed how the framework of linear elastic fracture mechanics (LEFM) can be used to characterize the stress field around singularities and the associated risk of failure. These two criteria and the finite element method, allow analysing how a thermal loading history may modify the risk of failure of DBC substrates. It was shown, in particular, that three overcooling cycles should produce an “overload retardation effect”. Experimentally, applying three “overload cycles” (−70 °C, +180 °C), prior to thermal fatigue cycles (−30 °C, +180 °C), increased very significantly the fatigue life of DBC substrates. This result shows that the fatigue life and the reliability of power electronic devices could be optimized using a thermo-mechanical approach of the problem and suitable failure criteria.
---
paper_title: A Reliability Model for Power MOSFETs Working in Avalanche Mode Based on an Experimental Temperature Distribution Analysis

paper_content:

The on-state resistance of power MOSFET devices tasked to perform repetitive avalanche operations is subject to modifications caused by the growth of voids and cracks in the source metallization. Endurance tests are the traditional way to monitor these changes in order to assess device reliability. However, they are very time intensive, requiring even months of uninterrupted operations. An interesting alternative is assessment of reliability through a suitable model, but no standard techniques have been developed up until now to accomplish this task. A possible approach, dynamic analysis of the temperature distribution over the source metal, is presented in this paper. Coupling the results of the thermodynamic analysis with a reliability model, and based on the Coffin-Manson law, device degradation over time can be estimated and the level of reliability can be evaluated. The consistence of the obtained reliability prediction is confirmed by comparison with endurance test results. The described approach can be usefully applied to assess the reliability of MOSFETs in a large set of applications in the automotive field.
---
paper_title: Active thermal control of power electronics modules

paper_content:

Active thermal control techniques make it feasible to regulate the steady state and transient thermal-mechanical stress in power electronic modules for applications such as motor drives. On-line junction temperature estimation and manipulation of the switching frequency and current limit to regulate the losses, are used to prevent over-temperature and power cycling failures in IGBT power modules. The techniques developed in this work are used to actively control the junction temperature of the power module. This control strategy improves power module reliability and increases utilization of the silicon thermal capacity by providing sustained operation at maximum attainable performance limits.
---
paper_title: IGBT dynamics for clamped inductive switching

paper_content:

Clamped inductive switching performance of insulated gate bipolar transistors (IGBTs) have been studied in detail with the aid of extensive measurements and numerical simulations. Internal dynamics of a latch-up free punch-through IGBT during clamped inductive switching is studied using two-dimensional (2-D) mixed device and circuit simulations incorporating the self-heating mechanism. Failure of IGBT during inductive load turn-off is shown to occur due to thermally assisted carrier multiplication at the reverse biased p-base n-drift region junction under the emitter contact.
---
paper_title: Predicting the Reliability of Power Electronic Modules

paper_content:

This paper discusses the reliability of an IGBT power electronics module. This work is part of a major UK funded initiative into the design, packaging and reliability of power electronic modules. The predictive methodology combines numerical modeling techniques with experimentation and accelerated testing to identify failure modes and mechanisms for these type of power electronic module structures. The paper details results for solder joint failure substrate solder. Finite element method modeling techniques have been used to predict the stress and strain distribution within the module structures. Together with accelerated life testing, these results have provided a failure model for these joints which has been used to predict reliability of a rail traction application.
---
paper_title: Collapse of MOSFET drain current after soft breakdown

paper_content:

Gate-oxide soft breakdown (SB) can have a severe impact on MOSFET performance even when not producing any large increase of the gate leakage current. The SB effect on the MOSFET characteristics strongly depends on the channel width W: drain saturation current and MOSFET transconductance dramatically drop in transistors with small W after SB. As W increases, the SB effect on the drain current fades. The drain saturation current and transconductance collapse is due to the formation of an oxide defective region around the SB spot, whose area is much larger than the SB conductive path. Similar degradation can be observed even in heavy ion irradiated MOSFETs where localized damaged oxide regions are generated by the impinging ions without producing any increase of gate leakage current.
---
paper_title: Power cycling reliability of IGBT power modules

paper_content:

The goal of this study was to understand the power cycling reliability of IGBT power modules. These power modules are made up of multi-layer stacks and consist of multiple power dice in parallel. The interconnection schemes within the module include leadframes soldered to substrate, die attachment using solder and wirebonds. Thermal and power cycling fatigues material interfaces because of the CTE mismatch between dissimilar materials. In addition, wirebonds on the dice are prone to debonding because of the thermally induced stresses. Tests were designed to understand the power cycling reliability of these large transistor modules. Results from the tests are summarized in this paper.
---
paper_title: Fast-clamped short-circuit protection of IGBT's

paper_content:

Identification of fault current during the operation of a power semiconductor switch and activation of suitable remedial actions are important for reliable operation of power converters. A short circuit is a basic and severe fault situation in a circuit structure, such as voltage-source converters. This paper presents a new active protection circuit for fast and precise clamping and safe shutdown of fault currents of the insulated gate bipolar transistors (IGBTs). This circuit allows operation of the IGBTs with a higher on-state gate voltage, which can thereby reduce the conduction loss in the device without compromising the short-circuit protection characteristics. The operation of the circuit is studied under various conditions, considering variation of temperature, rising rate of fault current, gate voltage value and protection circuit parameters. An evaluation of the operation of the circuit is made using IGBTs from different manufacturers to confirm the effectiveness of the protection circuit.
---
paper_title: Reliability Assessment of Solder Joints in Power Electronic Modules by Crack Damage Model for Wind Turbine Applications

paper_content:

Wind turbine reliability is an important issue for wind energy cost minimization, especially by reduction of operation and maintenance costs for critical components and by increasing wind turbine availability. To develop an optimal operation and maintenance plan for critical components, it is necessary to understand the physics of their failure and be able to develop reliability prediction models. Such a model is proposed in this paper for an IGBT power electronic module. IGBTs are critical components in wind turbine converter systems. These are multilayered devices where layers are soldered to each other and they operate at a thermal-power cycling environment. Temperature loadings affect the reliability of soldered joints by developing cracks and fatigue processes that eventually result in failure. Based on Miner’s rule a linear damage model that incorporates a crack development and propagation processes is discussed. A statistical analysis is performed for appropriate model parameter selection. Based on the proposed model, a layout for component life prediction with crack movement is described in details.
---
paper_title: Experimental behavior of single-chip IGBT and COOLMOS devices under repetitive short-circuit conditions

paper_content:

This work presents the behavior of single-chip insulated gate bipolar transistors (IGBT) devices under repetitive short-circuit operations. The 600 and 1200 V nonpunch through IGBTs as well as 600 V COOLMOS (trademark of Infineon Technologies) have been tested. The repetition of these severe working conditions is responsible for devices ageing, and results unavoidably in the components failure. A series of experimental tests were made in order to determine the number of short-circuit operations the devices can support before failure for different dissipated energies. The temperature influence has been also investigated. Results show two distinct failure modes depending on the dissipated energy during the tests. A critical value of short-circuit energy has been pointed out which separates these failure modes. Experimental and numerical investigations have been carried out in order to analyze these failure modes. A detailed analysis of the physical mechanisms occurring during the short-circuit failures for dissipated energies equal or lightly higher than the critical value is presented.
---
paper_title: A Novel Scheme Suitable for High-Voltage and Large-Capacity Photovoltaic Power Stations

paper_content:

The efficiency, power quality, and reliability of renewable energy power conversion systems are key factors for future industrial applications. This paper presents a novel scheme to improve the performances of high-voltage large-capacity photovoltaic (PV) power stations. The power conversion of the PV system is divided into two stages, i.e., dc/dc power conversion and dc/ac power conversion. In the dc/dc stage, many power units are connected in parallel, each one of which includes a PV array and a nonisolated dc/dc converter. The dc/ac power conversion is equivalent to a voltage source in series with a current source. Square wave converters, together with transformers, are employed for the voltage source, which is based on the multipulse technology of square wave superposition. Pulsewidth-modulated converters are employed for the current source. Simulated waveforms with a whole 10-MVA/10-kV PV system are shown, and experimental results with a 100-kVA/1-kV dc/ac prototype are displayed.
---
paper_title: Cascaded DC-DC converter connection of photovoltaic modules

paper_content:

New residential scale photovoltaic (PV) arrays are commonly connected to the grid by a single DC-AC inverter connected to a series string of PV modules, or many small DC-AC inverters which connect one or two modules directly to the AC grid. This paper shows that a "converter-per-module" approach offers many advantages including individual module maximum power point tracking, which gives great flexibility in module layout, replacement, and insensitivity to shading; better protection of PV sources, and redundancy in the case of source or converter failure; easier and safer installation and maintenance; and better data gathering. Simple nonisolated per-module DC-DC converters can be series connected to create a high voltage string connected to a simplified DC-AC inverter. These advantages are available without the cost or efficiency penalties of individual DC-AC grid connected inverters. Buck, boost, buck-boost and Cuk converters are possible cascadable converters. The boost converter is best if a significant step up is required, such as with a short string of 12 PV modules. A string of buck converters requires many more modules, but can always deliver any combination of module power. The buck converter is the most efficient topology for a given cost. While flexible in voltage ranges, buck-boost and Cuk converters are always at an efficiency or alternatively cost disadvantage.
---
paper_title: Topology Study of Photovoltaic Interface for Maximum Power Point Tracking

paper_content:

This paper looks at the performance of photovoltaic modules in nonideal conditions and proposes topologies to minimize the degradation of performance caused by these conditions. It is found that the peak power point of a module is significantly decreased due to only the slightest shading of the module, and that this effect is propagated through other nonshaded modules connected in series with the shaded one. Based on this result, two topologies for parallel module connections have been outlined. In addition, dc/dc converter technologies, which are necessary to the design, are compared by way of their dynamic models, frequency characteristics, and component cost. Out of this comparison, a recommendation has been made
---
paper_title: Fault Diagnosis and Reconfiguration for Multilevel Inverter Drive Using AI-Based Techniques

paper_content:

A fault diagnostic and reconfiguration method for a cascaded H-bridge multilevel inverter drive (MLID) using artificial-intelligence-based techniques is proposed in this paper. Output phase voltages of the MLID are used as diagnostic signals to detect faults and their locations. It is difficult to diagnose an MLID system using a mathematical model because MLID systems consist of many switching devices and their system complexity has a nonlinear factor. Therefore, a neural network (NN) classification is applied to the fault diagnosis of an MLID system. Multilayer perceptron networks are used to identify the type and location of occurring faults. The principal component analysis is utilized in the feature extraction process to reduce the NN input size. A lower dimensional input space will also usually reduce the time necessary to train an NN, and the reduced noise can improve the mapping performance. The genetic algorithm is also applied to select the valuable principal components. The proposed network is evaluated with simulation test set and experimental test set. The overall classification performance of the proposed network is more than 95%. A reconfiguration technique is also proposed. The proposed fault diagnostic system requires about six cycles to clear an open-circuit or short-circuit fault. The experimental results show that the proposed system performs satisfactorily to detect the fault type, fault location, and reconfiguration.
---
paper_title: The SEU in pulse width modulation controllers with soft start and shutdown circuits

paper_content:

A study was done of Single Event Upset (SEU) in pulse width modulation (PWM) controllers which feature either soft start or shutdown circuits. Upsets occurring in the soft start circuit of these devices may greatly effect the external circuit depending on the configuration of the PWM.
---
paper_title: State-of-the-art Power Module Design for Renewable Energy Application

paper_content:

Renewable energy application needs power modules to control the regenerated power. Standard power modules are suitable but not optimized for the tough requirements of this application. In this paper, we will introduce the requirements and the state-of-the-art IGBT modules for renewable energy application. A detailed explanation of a state of the art IGBT module up to a finished high power windmill converter will be discussed.
---
paper_title: Reliability assessment of fault-tolerant Dc-Dc converters for photovoltaic applications

paper_content:

A framework for integrating performance and reliability analysis of switch-mode, dc-dc power converters employed as front ends in photovoltaic energy processing applications is presented. The proposed approach acknowledges the influence of the converter's steady-state operation on device failure rates. Markov reliability models are derived to assess reliability-oriented metrics of the system. The conceptual background is elucidated in the context of a topologically-redundant dc-dc converter, and the dependence of the Mean Time to Failure on design parameters is explored. The subtle affiliation between power-electronics design and system reliability is assessed through several case studies.
---
paper_title: Fault-Tolerant Reconfiguration System for Asymmetric Multilevel Converters Using Bidirectional Power Switches

paper_content:

Asymmetric multilevel converters can optimize the number of levels by using H-bridges scaled in the power of three. The shortcoming of this topology is that the H-bridges are not interchangeable, and then, under certain faulty conditions, the converter cannot operate. A reconfiguration system based on bidirectional electronic valves has been designed for three-phase cascaded H-bridge inverters. Once a fault is detected in any of the insulated gate bipolar transistors of any H-bridge, the control is capable to reconfigure the hardware keeping the higher power bridges in operation. In this way, the faulty phase can continue working at the same voltage level by adjusting its gating signals. Some simulations and experiments with a 27-level inverter, to show the operation of the system under a faulty condition, are displayed.
---
paper_title: Passivity-Based Controllers for the Stabilization of DC-to-DC Power Converters

paper_content:

Abstract Passivity-based feedback controllers are derived for the indirect stabilization of the average output voltage in pulse-width-modulation (PWM) controlled DC-to-DC power converters of the ‘boost’, ‘buck-boost’, and ‘buck’ types. The controller design is carried out on the basis of well-known average PWM models of such circuits. The average models are first shown to be Euler-Lagrange systems corresponding to a suitable set of average Euler-Lagrange parameters. The proposed regulators are based on an ‘energy shaping plus damping injection’ scheme, achievable through nonlinear dynamical feedback. The performance of the proposed passivity-based duty ratio synthesis policies is tested for the ‘boost’ converter case. The regulating feedback law, derived on the basis of a ‘boost’ model composed of ideal switches and ideal circuit components, is assessed, via computer simulations, on a realistic stochastically perturbed switched converter model, including parasitic resistances and parasitic voltage sources.
---
paper_title: Expert systems for fault diagnosis of VSI fed AC drives

paper_content:

The use of a rule-based expert system for fault diagnosis of a voltage source inverter (VSI) feeding an induction motor are presented. Interactive session between the user and the expert system is employed to determine the faulty device(s) of the VSI fed drive. Based on the response of the operator, the functional and connectivity information coded in the knowledge base of the expert system diagnoses a fault and corrective measures and advice are given. This could result in an increase in the system availability, reliability, safety, and a reduction in maintenance cost and down time. >
---
paper_title: Reliability improvement of isolated generating systems by photovoltaic ac fusion converters

paper_content:

In the case of isolated areas, power quality and service reliability are improved by fusion of the ac power generation with a PV system output. Such an arrangement decreases the operating costs considerably. The proposed model and the related reliability and performance indices illustrate the benefits of PV system fusion with ac generation.
---
paper_title: Grid Connected PV Systems: A Reliability-Based Comparison

paper_content:

This paper presents the reliability prediction of four photovoltaic systems: a two-stages system, a three-stages one, and two integrated topologies, one with a boost-inverter, and the second with a buck-boost inverter. The goal is to identify the most failure prone components, and the stress factors with the highest contribution to the failure rate. In all cases, it was found that the MOSFETs are the most vulnerable components, and that the dominant stress factor is related to the temperature. It was also found that the reliability can be improved if the switching devices are overrated, but only to a certain level, and using too large MOSFET can be counterproductive.
---
paper_title: Power electronic device temperature estimation and control in pulsed power and converter applications

paper_content:

Reliable functioning of a power electronic switching device is limited not only by the instantaneous device junction temperature but also by its variation. A technique for reducing the device temperature variation is described. A simplified mathematical model of the thermal process in the device is evaluated in real time to estimate the instantaneous device temperature. A temperature control loop adjusts the device switching losses to compensate changes in conduction loss, thus keeping the total losses, and hence the temperature, substantially constant. This principle is applied to a pulsed power supply and to a PWM converter operating at a very-low-frequency (0.1 Hz) output power modulation. The amplitude of device temperature variations is reduced by at least 50%.
---
paper_title: Three-Level Converter Topologies With Switch Breakdown Fault-Tolerance Capability

paper_content:

This paper presents some modified topologies of the neutral-point-clamped converter. In all of them, the main change consists of adding a fourth leg, which is based on the flying-capacitor converter structure. The aim of this additional leg is to provide the converter with fault tolerance. Furthermore, during normal operation mode, this leg is able to provide a stiff neutral voltage. Consequently, the low-frequency voltage oscillations that appear at the neutral point of the standard three-level topology in some operating conditions no longer exist. As a result, the modulation strategy of the three main legs of the converter does not have to take care of voltage balance, and it can be designed to either achieve optimal output voltage spectra or improve the efficiency of the converter. Simulation and experimental results are presented to show the viability of this approach both under normal operation mode and in the event of faults.
---
paper_title: Designing a compact soft-start scheme for voltage-mode DC-DC switching converters

paper_content:

In this paper, a compact soft-start scheme is proposed and successfully applied to typical voltage-mode DC-DC switching converters. The adaptive current limitation implemented through DAC control will largely reduce the overshoot voltage under a wide range of output current. Proven experimentally by a buck converter implemented in a [email protected] CMOS technology, the post-simulation results show that when the converter starts up, the maximum overshoot (2.7% at I"L"O"A"D=0A) by the proposed soft-start scheme is less than that with the conventional scheme by 5% under the same condition. The start-up time can be adaptively adjustable depending on load current and the maximum start-up time is around [email protected] with [email protected] output capacitor. The circuits which realize the soft-start scheme can also be fully integrated into the control chip of DC-DC switching converter resulting in low cost.
---
paper_title: Differential Power Processing for Increased Energy Production and Reliability of Photovoltaic Systems

paper_content:

Conventional energy conversion architectures in photovoltaic (PV) systems are often forced to tradeoff conversion efficiency and power production. This paper introduces an energy conversion approach that enables each PV element to operate at its maximum power point (MPP) while processing only a small fraction of the total power produced. This is accomplished by providing only the mismatch in the MPP current of a set of series-connected PV elements. Differential power processing increases overall conversion efficiency and overcomes the challenges associated with unmatched MPPs (due to partial shading, damage, manufacturing tolerances, etc.). Several differential power processing architectures are analyzed and compared with Monte Carlo simulations. Local control of the differential converters enables distributed protection and monitoring. Reliability analysis shows significantly increased overall system reliability. Simulation and experimental results are included to demonstrate the benefits of this approach at both the panel and subpanel level.
---
paper_title: Photovoltaic array driven adjustable speed heat pump and power system scheme for a lunar based habitat

paper_content:

A high reliability power system scheme, incorporating a photovoltaic power supply and adjustable speed heat pump for life support is presented in this paper. Initial design guidelines and also a description of the state of technology available is presented herein. The power supply scheme will be used as input to an adjustable speed drive (ASD) which will drive a heat pump. A brief study of various aspects of ASDs is presented; further a summary of the relative merits of different ASD systems presently in vogue is discussed. The advantages of using microcomputer based ASDs is widely understood and accepted. Of the three most popular drive systems, namely the induction motor drive, switched reluctance motor drive and brushless DC motor drive, any one may be chosen. The choice would depend on the nature of the application and its requirements. The suitability of the above mentioned drive systems and control techniques for photovoltaic array driven ASD for an aerospace application are discussed. Also discussed are several possible power system designs for a potential lunar habitat.
---
paper_title: STATE OF THE ART OF DV / DT AND DI / DT CONTROL OF INSULATED GATE POWER SWITCHES

paper_content:

IGBT and MOSFET power switches are commonly used in power converters. MOSFET for middle power and IGBT for high power converters : gate drive circuits are used to drive such components. Some applications need to control dv/dt and di/dt from power switches to reduce electromagnetic emissions. New solutions have been introduced and tested since 1990 (conresponding to the maturation of IGBT technology). This article is about a state of the art of di/dt and dv/dt methods. The authors propose original solutions with simulations and experimental results on 1200A-3300V IGBT modules.
---
paper_title: Soft Start Strategy for Bi-directional DC-DC Converter

paper_content:

Traditional soft start method will give rise to large inverse inductor current at startup of bi-directional converter at double sources application, and result in damage of devices. This paper proposes a novel soft start strategy-two-phase soft start strategy to implement soft start at double sources application, which can avoid inverse inductor current. Experimental results are given to verify the effectiveness of two-phase soft start strategy.
---
paper_title: Reliability Issues in Photovoltaic Power Processing Systems

paper_content:

Power processing systems will be a key factor of future photovoltaic (PV) applications. They will play a central role in transferring, to the load and/or to the grid, the electric power produced by the high-efficiency PV cells of the next generation. In order to come up the expectations related to the use of solar energy for producing electrical energy, such systems must ensure high efficiency, modularity, and, particularly, high reliability. The goal of this paper is to provide an overview of the open problems related to PV power processing systems and to focus the attention of researchers and industries on present and future challenges in this field.
---
paper_title: A Frequency-Control Approach by Photovoltaic Generator in a PV–Diesel Hybrid Power System

paper_content:

A photovoltaic (PV) system's output power fluctuates according to the weather conditions. Fluctuating PV power causes frequency deviations in the power utilities when the penetration is large. Usually, an energy storage system (ESS) is used to smooth the PV output power fluctuations and then the smoothed power is supplied to the utility. In this paper, a simple fuzzy-based frequency-control method is proposed for the PV generator in a PV-diesel hybrid system without the smoothing of PV output power fluctuations. By means of the proposed method, output power control of a PV generator considering the conditions of power utilities and the maximizing of energy capture are achieved. Here, fuzzy control is used to generate the PV output power command. This fuzzy control has average insolation, change of insolation, and frequency deviation as inputs. The proposed method is compared with a maximum power point tracking control-based method and with an ESS-based conventional control method. The numerical simulation results show that the proposed method is effective in providing frequency control and also delivers power near the maximum PV power level.
---
paper_title: An industry-based survey of reliability in power electronic converters

paper_content:

A questionnaire survey was carried out to determine the industrial requirements and expectations of reliability in power electronic converters. According to the survey, power semiconductor devices ranked the most fragile components. It was concluded that main stresses were from the environment, transients and heavy loads, which should be considered during power electronic system design and normal operation. Further analyses suggest that power device reliability is a key issue and power electronic converter design is correlated with failure costs.
---
paper_title: A robustly stable output feedback saturated controller for the boost DC-to-DC converter ☆

paper_content:

Abstract The problem of regulating the output voltage of the Boost DC-to-DC power converter has attracted the attention of many control researchers for several years now. Besides its practical relevance, the system is an interesting theoretical case study because it is a switched device whose averaged dynamics are described by a bilinear second order nonminimum phase system with saturated input, partial state measurement and a highly uncertain parameter – the load resistance. In this paper we propose an output-feedback saturated controller which ensures regulation of the desired output voltage and is, at the same time, insensitive to uncertainty in the load resistance. Furthermore, bounds on this parameter can be used to tune the controller so as to (locally) ensure robust performance, e.g., that the transient has no (under) over-shoot. The controller, which is designed following the passivity-based interconnection and damping assignment methodology recently proposed in the literature, is a static nonlinear output feedback. This allows us to invoke simple phase-plane techniques to determine the exact domain of attraction as well as the admissible initial conditions that ensure the control objectives. One final advantage of our controller is that it is computationally less demanding than the industry standard lead-lag filters.
---
paper_title: Analysis of high-power IGBT short circuit failures

paper_content:

The next linear collider (NLC) accelerator proposal at Stanford Linear Accelerator Center (SLAC, Menlo Park, CA), requires a highly efficient and reliable, low cost, pulsed-power modulator to drive the klystrons. A solid-state induction modulator has been developed at SLAC to power the klystrons; this modulator uses commercial high voltage and high current insulated gate bipolar transistor (IGBT) modules. Testing of these IGBT modules under pulsed conditions was very successful; however, the IGBTs failed when tests were performed into a low inductance short circuit. The internal electrical connections of a commercial IGBT module have been analyzed to extract self- and mutual partial inductances for the main current paths as well as for the gate structure. The IGBT module, together with the partial inductances, has been modeled using PSpice. Predictions for electrical paths that carry the highest current correlate with the sites of failed die under short circuit tests. A similar analysis has been carried out for a SLAC proposal for an IGBT module layout. This paper discusses the mathematical model of the IGBT module geometry and presents simulation results.
---
paper_title: Overcurrent Protection on Voltage-Source-Converter-Based Multiterminal DC Distribution Systems

paper_content:

This paper proposes a protection scheme which utilizes modern voltage-source converters as fast-acting current-limiting circuit breakers. This paper investigates the main challenges of detecting and localizing a fault, and interrupting it as quickly as possible in a multiterminal dc system. A system protection scheme consisting of smart relays associated with converters has been developed. The protection relays monitor local quantities to detect and isolate disturbances/faults. It is shown that overcurrent-based schemes can be adopted for these relays to meet the fast response requirements. The effectiveness of the proposed protection scheme is illustrated through simulations
---
paper_title: Nonlinear control laws for switching power converters

paper_content:

Nonlinear control laws for switching power converters are explored, using an up-down converter as a vehicle. A nonlinear change of variables is used to transform the usual state-space description into one that is more amenable to design of a sliding mode control. Results of numerical simulations and of a microprocessor implementation based on look-up tables are presented.
---
paper_title: Photovoltaic DC-Building-Module-Based BIPV System—Concept and Design Considerations

paper_content:

The photovoltaic (PV) modules used in the building-integrated PV (BIPV) system, generally, can be installed in different orientations and angles. Moreover, performance of the PV modules is easy to be affected by partial shadows and mismatch of their electrical parameters. Consequently, the conventional power configurations are difficult to obtain higher energy efficiency and reliability. Some improved power configurations of BIPV system have been presented to solve these problems. The objective of the paper is to give an overview of the existing solutions, and then, proposes an efficient and cost-effective power configuration of BIPV system from the energy conversion and control point of view. The proposed power configuration consists of plenty of PV dc-building module (PV-DCBM) and a centralized inverter. Each PV-DCBM includes a high step-up dc-dc converter integrated with a PV module into an individual electrical device. The PV-DCBMs are parallel connected, and then, connected to a common dc bus. The centralized inverter is connected to the grid. The design criterions, optimum design considerations, and design procedure of the proposed PV-DCBM-based BIPV system are proposed in this paper. The experimental results are presented to verify the validity and feasibility of the novel concept.
---
paper_title: Switching Strategies for Fault Tolerant Operation of Single DC-link Dual Converters

paper_content:

This paper proposes a method that allows the operation with direct torque control under incipient faults of the power switching devices in single dc-link dual inverters. Once the fault onset of the switching device is detected, the troubled devices are put under trigger suppression to regain operation. The proposed control algorithm makes use of additional states, termed opportunistic states, to maintain control of the induction machine. Simulations and experimental results confirm the capabilities of the technique for up to six devices under trigger suppression.
---
paper_title: Reliability-Oriented Assessment of a DC/DC Converter for Photovoltaic Applications

paper_content:

There is a trend toward increasing the performance of power electronics converters used in photovoltaic systems. However, parameters such as reliability, efficiency, and complexity might be in conflict. In this paper, the design of a simple DC/DC interleaved boost converter is assessed. It takes advantage of state-of-the-art power devices that have fast switching times. It is shown that requirements of low complexity, high reliability, and high efficiency can be satisfied, without resorting to switching aids, provided that the devices are selected with reliability in mind. A 1 kW prototype attained a peak efficiency as high as 98%, and a predicted mean time between failures of 100,000 hours at 80 C.
---
paper_title: Current Sensor Fault Detection, Isolation, and Reconfiguration for Doubly Fed Induction Generators

paper_content:

Fault tolerance is gaining growing interest to increase the reliability and availability of distributed energy sources. Current sensor fault detection, isolation, and reconfiguration are presented for a voltage-oriented controlled doubly fed induction generator, which is mainly used in wind turbines. The focus of this analysis is on the isolation of the faulty sensor and the actual reconfiguration. During a short period of open-loop operation, the fault is isolated by looking at residuals calculated from observed and measured signals. Then, replacement signals from observers are used to reconfigure the drive and reenter closed-loop control. Laboratory measurement results are included to prove that the proposed concept leads to good results.
---
paper_title: Insulated gate bipolar transistor reliability testing protocol for PV inverter applications

paper_content:

To decrease the cost of ownership of photovoltaic systems, less costly and more reliable photovoltaic inverters must be developed. Insulated gate bipolar transistors are a significant cause of inverter failures and system inefficiencies, so a thorough understanding of their strengths and weaknesses with regards to inverters is necessary. This paper summarizes the current state of experimentation surrounding the use of IGBTs in photovoltaic inverters and discusses their construction, use, lifetime, and reliability of IGBTs regularly used in photovoltaic inverters. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
---
paper_title: Evaluation of a photovoltaic energy mechatronics system with a built-in quadratic maximum power point tracking algorithm

paper_content:

The historically high cost of crude oil price is stimulating research into solar (green) energy as an alternative energy source. In general, applications with large solar energy output require a maximum power point tracking (MPPT) algorithm to optimize the power generated by the photovoltaic effect. This work aims to provide a stand-alone solution for solar energy applications by integrating a DC/DC buck converter to a newly developed quadratic MPPT algorithm along with its appropriate software and hardware. The quadratic MPPT method utilizes three previously used duty cycles with their corresponding power outputs. It approaches the maximum value by using a second order polynomial formula, which converges faster than the existing MPPT algorithm. The hardware implementation takes advantage of the real-time controller system from National Instruments, USA. Experimental results have shown that the proposed solar mechatronics system can correctly and effectively track the maximum power point without any difficulties.
---
paper_title: A photovoltaic panel emulator using a buck-boost DC/DC converter and a low cost micro-controller

paper_content:

Abstract In order to facilitate the design and testing of photovoltaic (PV) power systems, a PV emulator which models the electrical characteristic of a PV panel or array is needed. Among different approaches to modeling PV characteristic, namely the I – V curve, curve-fitting is a popular approach. Even though a single high-order polynomial equation may accurately represent the I – V curve, the process of derivation and implementation is rather complex. This paper hence proposes the use of piecewise linear approach which is easier to derive and implement in a low-cost micro-controller. A two-switch buck-boost DC/DC converter is selected as the PV emulator and is analyzed. Experimental results on a hardware prototype of the proposed PV emulator are reported to show the effectiveness of the approach.
---
paper_title: Open-Circuit Fault Diagnosis and Fault-Tolerant Strategies for Full-Bridge DC–DC Converters

paper_content:

This paper proposes a four-step open-circuit fault diagnosis and fault-tolerant scheme for isolated phase-shifted full-bridge (PSFB) dc-dc converters to improve the reliability. The fault diagnostic method utilizes the primary voltage of the transformer as the diagnostic criterion, which can be obtained easily by adding an auxiliary winding. When an open-circuit fault occurs in any switch of the PSFB converter, the proposed fault detection method can generate an indication of the abnormal state and trigger an active-phase-shifted in the control system. Under the APS state, it is very easy to locate the exact position of faulty switch because the voltage waveform of the primary winding heavily depends on the location of the faulty switch. After locating the position of the faulty switch, the PSFB converter is reconfigured into an asymmetrical half-bridge (AHB) converter by turning ON the normal switch in the faulty leg and adding a redundant winding to the secondary side. Therefore, the rebuilt AHB converter can keep the output voltage constant under a reduced power rating after the open-circuit fault. The operational principle, design consideration, and implementation are discussed in this paper. The experimental results are given to verify the validity of theoretical analysis. The proposed strategies outperform the traditional schemes in terms of cost, reliability, and power density.
---
paper_title: Reliability Considerations for Parallel Performance of Semiconductor Switches in High-Power Switching Power Supplies

paper_content:

In order to ensure increasing current rating of semiconductor switches, paralleling is unavoidable. In this paper, the paralleling of switches has been studied from the reliability point of view. A prototype 4-kW boost converter has been used for this paper. In this boost converter, five insulated gate bipolar transistors are paralleled per switch in order to increase the current rating. Based on experimental results, the reliability of converter has been calculated. Results of reliability calculations showed that paralleling switches extremely decreases reliability of DC-DC converters. The same converter has been constructed by using an integrated power module (IPM). The same calculations have been repeated for the IPM-based converter. The comparison of the results shows that the case of IPM in converters can increase the reliability of the circuit.
---

Title: Power Switch Faults, Diagnosis and Tolerant Schemes in Converters of Photovoltaic Systems- A Review

Section 1: Introduction
Description 1: This section introduces the topic of power switch faults, the significance of early failure detection, and the importance of developing fault tolerance in converters within photovoltaic systems.

Section 2: Known Failure Reasons in Power Switches
Description 2: This section describes the common failure mechanisms of power switches used in converters, including thermal stress, mechanical stress, material factors, and specific failure modes related to MOSFETs and IGBTs.

Section 3: Role of Converters in Photovoltaic Applications
Description 3: This section discusses the function of converters within photovoltaic systems, focusing on inverter and DC-DC converter roles, various topologies, and MPPT algorithms aimed at improving efficiency and reliability.

Section 4: Converter Failures, Fault Diagnosis, and Tolerant Schemes
Description 4: This section explores different fault diagnosis and fault-tolerant methodologies used in converters, analyzing industrial survey data, specific fault modes in MOSFETs and IGBTs, and various modeling and simulation techniques for fault prediction and assessment.

Section 5: Conclusion
Description 5: This section summarizes the discussed topics, emphasizing the necessity of advancements in power switch construction, better thermal management, improved reliability, and fault tolerance in converters for photovoltaic systems.