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In this article, an optimized fault-tolerant control (FTC) method without current judgement is proposed for open-switch faults (OSFs) in dual three-phase permanent magnet synchronous motor (DTPMSM) drives. The reason for the torque ripple under OSFs has been investigated. The theoretical analysis reveals a significant increase in torque ripple under OSFs. Then, an optimized FTC method is proposed for a DTPMSM with two isolated neutral points. The proposed method maintains the original control scheme, enabling the smooth transitions of current and torque between faulty operation and FTC without introducing noticeable torque ripples. In addition, the universality and robustness are enhanced by eliminating the need for current judgement, thereby avoiding misjudgments due to sinusoidal current zero crossings, sudden load, or speed changes. The experimental results are presented to validate the effectiveness of the proposed FTC strategy under OSFs on a laboratory DTPMSM. [ABSTRACT FROM AUTHOR]

In this article, an optimized fault-tolerant control (FTC) method without current judgement is proposed for open-switch faults (OSFs) in dual three-phase permanent magnet synchronous motor (DTPMSM) drives. The reason for the torque ripple under OSFs has been investigated. The theoretical analysis reveals a significant increase in torque ripple under OSFs. Then, an optimized FTC method is proposed for a DTPMSM with two isolated neutral points. The proposed method maintains the original control scheme, enabling the smooth transitions of current and torque between faulty operation and FTC without introducing noticeable torque ripples. In addition, the universality and robustness are enhanced by eliminating the need for current judgement, thereby avoiding misjudgments due to sinusoidal current zero crossings, sudden load, or speed changes. The experimental results are presented to validate the effectiveness of the proposed FTC strategy under OSFs on a laboratory DTPMSM.

This study explores a method for detecting and isolating faults in wind power conversion systems that use a permanent magnet synchronous generator (PMSG). The goal is to enhance the reliability of the inverter by implementing an fault detection method and fault-tolerant control. The converter incorporates an extra leg with two switches that can be quickly connected in place of a malfunctioning leg, ensuring continued operation. Our fault detection and isolation module employs a threshold-based approach, utilizing real-time signal measurements to identify anomalies exceeding predefined limits. The experimental validation of this module is conducted on a high-performance dSpace DS1104 controller board using MATLAB Simulink. Finally, a real-world experiment was conducted to confirm the effectiveness of the proposed fault detection and isolation (FDI) algorithm. The results successfully demonstrated the algorithm’s ability to detect and isolate switch faults. [ABSTRACT FROM AUTHOR]

Recently, fault-tolerance control (FTC) methods have been proposed to further improve the reliability of T-type three-level converters. However, the application of model predictive control (MPC) in FTCs is rare, and the neutral point (NP) voltage imbalance before an open-switch fault occurs has not been solved. This article focuses on these two problems and proposes two FTC control methods: sequential MPC and sequential model predictive tolerance control. Both methods are implemented by designing a sequential predictive control that first considers the NP voltage balance and then grid current tracking. Through the staggered operation of the two methods, a T-type grid-connected converter with an LCL filter can operate normally after an open-switch fault occurs. Moreover, both methods can achieve the NP voltage balance and excellent grid current outputs, eliminate the time-consuming selection of weighting factors, and reduce the number of calculation loops compared with the traditional model predictive tolerance control, thereby improving the control flexibility. The performance and comparison of the open-switch FTC with respect to the NP voltage oscillations, total harmonic distortion of the grid current, and pole voltage were demonstrated using numerous simulation and experimental results. [ABSTRACT FROM AUTHOR]

The open-switch fault of three-phase voltage source rectifiers (VSR) may lead to ac current distortion. In the past decade, some current-based fault diagnosis methods have been proposed, which directly used the phenomenon of current distortion but lacked a detailed analysis of the cause of it. In this paper, the current distortion of VSR with unity power factor operation is analyzed from two aspects: the effect of the three-phase switching state on the ac current and the response of the VSR control system after the fault. Besides, the impact of the VSR system and control parameters on the current distortion is also discussed. The analysis verifies the feasibility of the distortion current for fault diagnosis, providing a theoretical basis for current-based fault diagnosis methods of VSRs. To substantiate the analysis of the distorted current, we designed a simplified fault diagnosis method, which determined the faulty phase by the difference of the normalized three-phase distorted current, and located the faulty switch by the grid voltage angle. The experiments are conducted to verify the analysis of current distortion and the reliability of the proposed fault diagnosis method.

In this article, a minimum-copper-loss fault-tolerant control scheme is proposed for open-phase fault and open-switch fault of dual three-phase permanent magnet synchronous motor (DT-PMSM) drives. Both the winding configurations of isolated neutral points and connected neutral points are studied in this article. In conventional minimum-copper-loss fault-tolerant control schemes, the constraints of sinusoidal phase currents result in insufficient copper-loss reduction. Different from them, the current references with the theoretically lowest copper losses are first derived and applied for different fault cases of DT-PMSM drives without using any unnecessary constraints in the proposed fault-tolerant control scheme. Thus, all phase currents in the proposed minimum-copper-loss fault-tolerant control scheme are optimized to be nonsinusoidal waveforms. Besides, the copper losses are further reduced by fully utilizing the remaining healthy switch in the faulty inverter leg for the open-switch fault of DT-PMSM drives with the proposed scheme. It has been theoretically and experimentally proved that the proposed fault-tolerant control scheme can reduce copper losses than all existing fault-tolerant schemes for both open-phase fault and open-switch fault in typical two-level voltage-source-inverter-fed DT-PMSM drives. [ABSTRACT FROM AUTHOR]

A standard three-phase motor drive means a typical two-level voltage source inverter fed three-phase motor drive without any auxiliary circuits. Without fault-tolerant control, common open-circuit faults will cause the breakdown of the standard three-phase motor drives. Although the torque pulsation is theoretically inevitable under the open-circuit faults of standard three-phase motor drives, it's still meaningful to improve the fault-tolerant capability of standard three-phase drives to prolong the reliable operation. In this article, a current optimization based fault-tolerant control is proposed to minimize the proportion of torque loss for standard three-phase permanent-magnet synchronous motor (PMSM) drives under open-phase fault and open-switch fault conditions. Firstly, a two-mode current control is designed to minimize the proportion of torque loss without changing the mathematical model of the faulty motor. Secondly, a three-mode current control is proposed and combined with adjustment of pulse width to tolerate the open-switch faults. Instead of removing the faulty inverter leg directly, the remaining healthy switch in the faulty inverter leg is still utilized. In this way, the damage from torque pulsation can be relieved in the aspect of both frequency and intensity. Finally, the validity of the proposed fault-tolerant control is verified by experiments. [ABSTRACT FROM AUTHOR]

To utilize the solar photovoltaic (PV) energy efficiently, dc–dc converters are widely used in both grid-connected and stand-alone systems. Among the various topologies, interleaved dc–dc boost converter offers the benefit of modularity, high power density, and high efficiency along with reduced input current ripple to the PV panel, thereby improving its power extraction efficiency. Open-circuit faults in any of the semiconductor switches of interleaved boost converter could lead to unequal loading on the healthy phases and increase in ripple current that reduces the extraction efficiency of the PV system. To address this issue, a new fault detection and localization scheme is proposed in this article. The proposed scheme utilizes the switching-frequency-based harmonic component for fault detection and localization. Once the fault is localized, a postfault restoration and control strategy is also proposed to ensure equal current sharing among the remaining healthy modules within their maximum current rating and minimize the input current ripple in the PV panel. Detailed simulations are carried out to show the effectiveness of the proposed approach. A laboratory prototype of the interleaved converter is built to validate the proposed approach and experimental test results are provided. [ABSTRACT FROM AUTHOR]

The fault diagnosis in multilevel converters is of great importance since they are comprised of more solid-state switches, compared with the conventional two-level converters. In this article, we propose a fast and efficient real-time fault detection and faulty component identification for an open-switch fault diagnosis based on the failure-mode algorithm for a single-phase five-level neutral-point-clamped inverter. Component modeling, complicated calculations, and load parameters are not required for realizing the proposed approach. Furthermore, the proposed strategy does not require any extra sensors. The signals already available in the control system, such as the applied switching pattern and terminal voltage, fulfill the fault diagnosis. Thanks to the proposed fault detection strategy, any misdiagnosis arising from noise existence, response time of the sensors, turn on and turn off delay times of the power switches, and measurement errors are avoided. The simulations and experiments are carried out to confirm the performance and effectiveness of the presented strategy. [ABSTRACT FROM AUTHOR]

In this paper, the problem of open-switch faults of a voltage source inverter system is investigated. A new fault diagnosis method based on an observer and an adaptive threshold is proposed. This method only needs to utilize the signals existing in a system without the need for extra hardware circuits. First, an observer is designed on a model of a three-phase voltage source inverter system to estimate currents. Then, an adaptive threshold is designed on fault residuals, dynamics of the currents and variations of the system operating state. Moreover, the dead time and switching delay time are also included in the threshold to consider practical applications. Furthermore, to achieve on-line real-time diagnosis and to improve the reliability of the proposed method, the averages of the current residuals in a current fundamental period are defined as diagnostic variables. Finally, the reliability and effectiveness of the proposed method are verified by simulation and experiment results. [ABSTRACT FROM AUTHOR]

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This study investigates a real‐time fault diagnostic of a transportation system which needs two drives with fault‐tolerance capabilities. Owing to the constraints on the mass of the system and on the cost of the voltage source inverter, a drive with two six‐phase permanent magnet synchronous machines in series‐connection supplied by two six‐leg inverters is chosen. Despite the serial connection, independent control of the two machines and fault‐tolerance to open‐switch fault is ensured. Nevertheless, a fault detection identification (FDI) process is required for analysis and/or control reconfiguration. The proposed FDI is based on the combination of different criteria obtained from the two zero‐sequence currents and from the normalised currents mapped into two frames defined by the concordia transformation. Results obtained from simulation and experimental tests show the effectiveness of the proposal. [ABSTRACT FROM AUTHOR]

A cascaded H-bridge multilevel inverter is an indispensable part of high-power industrial drives. The multilevel inverters have an increased chance of switch fault as a consequence of a considerably large number of semiconductor switches associated in the power conversion. A quick and precise fault detection–isolation strategy improves the system reliability as well as reduces the shutdown time of the drive. This article presents a novel generalized open-switch fault-diagnostic approach for an $N$ -level cascaded H-bridge multilevel inverter. In this detection technique, half-cycle mean values of bridge voltages, which are calculated for positive and negative half cycles individually, are used as fault identification features. These means under open-switch fault are predicted from the reference half-cycle means and compared with those measured values to locate the open-switch fault. This quick detection scheme can identify the faulty switch within one fundamental period of output voltage for the cascaded inverters having different number of voltage levels. The computation requirement is minimum, since this approach does not need complex calculations or domain transformations. This strategy can efficiently locate the faulty switch of the cascaded inverter working with various level-shifted pulsewidth modulation schemes, different loading conditions, modulation indexes, and switching frequencies. The potency of the fault classification algorithm is verified through simulation and experimentation. [ABSTRACT FROM AUTHOR]

This paper presents a novel fault-tolerant method for active–neutral-point-clamped (ANPC) inverter using a modified carrier-based pulsewidth modulation. At a fault event, the ANPC inverter is divided into subinverters, and the modulating signal is modified to two modulating signals. The modified modulating signals are used to control the subinverters and allow continuous operation of the three-level ANPC inverter during faulty conditions even up to four open-switch faults per phase. This technique provides the fault-tolerant capability of the ANPC inverter without the need to add any additional phase legs or complex control strategies. Furthermore, the proposed technique ensures the voltage balancing of the dc-link capacitors. The performance of the proposed fault-tolerant technique is verified through simulation studies in MATLAB/Simulink under different faulty conditions. The feasibility of the proposed technique is also verified experimentally. [ABSTRACT FROM AUTHOR]

In this paper, diagnosis and tolerant control schemes have been studied for common electrical faults in T-type three-level inverter fed dual-three phase permanent magnet synchronous motor (PMSM) drives for safety-critical applications. Based on vector space decomposition and double three-phase space vector modulation, diagnostic and tolerant control methods have been developed comprehensively for open-phase faults, open-switch faults, and short-switch faults in T-type three-level inverter fed dual-three-phase PMSM drives, in such way that misdiagnosis of different faults sharing similar faulty features can be avoided. In particular, a two-step diagnostic scheme is proposed in order to simplify the diagnostic process. The first step is to identify the faulty phase and fault category by analyzing current trajectories on harmonic subspace, and the second step is to determine the specific fault type in a small fault-searching area obtained from the first step. In the aspect of fault-tolerant control, a novel current compensation method is proposed for open-phase fault without changing the machine model, space vector diagram, and control framework. Open-switch faults and short-switch faults are tolerated by making full use of the remaining vectors after faults. The validity of the proposed fault diagnosis and tolerance schemes has been verified by experiments. [ABSTRACT FROM AUTHOR]

In this paper, an open-switch fault diagnosis method for five-level H-Bridge Neutral Point Piloted (HB-NPP) or T-type converters is proposed. While fault tolerant operation is based on three steps (fault detection, fault localization and system reconfiguration), a fast fault diagnosis, including both fault detection and localization, is mandatory to make a suitable response to an open-circuit fault in one of the switches of the converter. Furthermore, fault diagnosis is necessary in embedded and safety critical applications, to prevent further damage and perform continuity of service. In this paper, we present an open-switch fault diagnosis method, based on the switches control orders and the observation of the converter output voltage level. In five-level converters such as HB-NPP and T-type topologies, some switches are mostly 'on' at the same time. Therefore, the fault localization is quite complicated. The fault diagnosis method we proposed is capable to detect and localize an open-switch fault in all cases. Computer simulations are carried out by using Matlab Simulink and SimPowerSystem toolbox to validate the proposed approach.

In this paper, a practical online open-switch fault detection method is presented. The proposed open-switch fault detection method is used to detect the open-circuited fault switch in the parallel inverters system. This method can relieve the severe effects of the over-current stress, to avoid the secondary fault to the electrical components in the parallel inverters system. This method is based on the detection of the resulting zero-sequence current, under the fault conditions. The proposed algorithm is activated by detecting the zero-sequence current between the parallel units, under the open-switch fault conditions. The sign of the resulting zero-sequence current is related to the upper or the lower open-switch fault case. The faulty phase identification relies on the analysis and the investigation of only the current measurements information of the faulty inverter. This method can get rid of the effects of the load, to obtain a reliable identification. The effectiveness of the proposed open-switch fault detection algorithm is theoretically analyzed and validated by the simulations and the experiments. [ABSTRACT FROM AUTHOR]

The mathematical modeling of open-switch faults in two-level machine-side converters and the fault-tolerant current control of isotropic permanent-magnet synchronous generators are discussed in this paper. The proposed converter model is generic for any open-switch fault and independent of the operation mode of the electrical machine. The proposed fault-tolerant current control system gives improved control performance and reduced torque ripple under open-switch faults by modifying the antiwindup strategy, adapting the space-vector modulation scheme, and by injecting additional reference currents. The theoretical derivations of model and control are validated by comparative simulation and measurement results. [ABSTRACT FROM AUTHOR]

In this article, a fault-tolerant voltage source inverter (VSI) is proposed for a novel topology of stand-alone doubly fed induction generator (DFIG) feeding an isolated DC load. In this topology, stator and rotor sides of DFIG are connected to DC-bus through a diode rectifier and VSI, respectively. The fault-tolerant VSI includes a redundant leg connected by bidirectional switches in order to replace the faulted leg and improve the reliability of the proposed system. The field oriented control strategy is adopted to control the d and q-axis rotor currents in order to maintain the voltage and the frequency at the output of the generator constant. A novel, easy and fast approach for fault detection and isolation (FDI) of open-switch damage in insulated gate bipolar transistor-based VSI is proposed in this study. This approach is developed using mathematical transformations such as a hysteresis detector, an integrator and a trigger. The FDI algorithm proposed here does not require the knowledge of the system model and is independent from its complexity. Simulations results are illustrated for a 3.7 kW DFIG feeding a DC load with open-switch fault in VSI that confirm the concepts proposed in this study. [ABSTRACT FROM AUTHOR]

The sliding mode control (SMC) is used to control variable structure systems such as power electronics converters. This paper presents a fault-tolerant strategy based on the SMC for current-controlled AC-DC converters. The proposed SMC is based on three sliding surfaces for the three legs of the AC-DC converter. Two sliding surfaces are assigned to control the phase currents since the input three-phase currents are balanced. Hence, the third sliding surface is considered as an extra degree of freedom which is utilised to control the neutral voltage. This action is utilised to enhance the performance of the converter during open-switch faults. The proposed fault-tolerant strategy is based on allocating the sliding surface of the faulty leg to control the neutral voltage. Consequently, the current waveform is improved. The behaviour of the current-controlled converter during different types of open-switch faults is analysed. Double switch faults include three cases: two upper switch fault; upper and lower switch fault at different legs; and two switches of the same leg. The dynamic performance of the proposed system is evaluated during healthy and open-switch fault operations. Simulation results exhibit the various merits of the proposed SMC-based fault-tolerant strategy. [ABSTRACT FROM AUTHOR]

In order to improve the reliability and availability of the converters of wind turbines, condition monitoring and fault diagnosis are considered crucial means to achieve these goals. In this text, according to the current variation characteristics of the converter, this paper presents a novel approach for real-time diagnostics of open-switch faults in back-to-back converters of a doubly fed wind turbine. The average value of the normalized converter phase currents and the absolute normalized currents are used as principal quantities to formulate the diagnostic variables. The proposed fault-diagnostic variables prove to be carrying information about multiple open-switch faults. In addition to, by the combination of these variables with the average absolute values of the normalized converter phase currents, an adaptive fault-diagnostic threshold is proposed, which ensures the robustness of the diagnosis of single and double open-switch faults. Finally, through the diagnostic variables and the adaptive threshold, the dynamic fault-diagnostic method for open-switch faults in the back-to-back converter of a doubly fed wind turbine is formed. The simulation and experimental results also indicate that the fault-diagnostic method can not only diagnose the multiple open-circuit faults of a back-to-back converter, but also have a better robustness. [ABSTRACT FROM PUBLISHER]

At present, pulse width modulation (PWM) technique is widely applied in motor drive systems. However, it may cause some unexpected effects: Bearing currents, overvoltage, power losses and unwanted noise. In some industrial cases, LC filters are always equipped in motor drive systems to suppress those unexpected effects. In order to improve the reliability and safety of the drive system, fault diagnostic strategies for power switches should be utilized as other drive systems without LC filters. In the literature, some open-switch diagnostic approaches are based on the observers derived from the mathematical models. However, the models are changed by the LC filters. Therefore, the existing approaches, based on the observers are failed, due to the change of the models. This study proposes an open-switch diagnostic method for permanent magnet synchronous motor (PMSM) drive equipped with LC Filter. The novelty of the proposed method is that the model of the LC filter is considered. Therefore, open-switch faults can be detected and located in the drive systems with LC filters. The switching function model of the drive system is analyzed at first. Then a sliding mode observer (SMO) considering the model of the filter is proposed to estimate the filter voltages and other state variables. Consequently, the faults can be detected and located through the residual errors between the expected and estimated filter voltages. This approach features simplicity. Furthermore, any extra sensors are not necessary. Experimental results on a 750-W PMSM drive system with an LC filter proved the feasibility of the proposed method.

This paper proposes a fault diagnosis and tolerant control methods for an open-switch fault caused in a three-phase three-level neutral-point-clamped (NPC) pulse-width modulation (PWM) active rectifier. The open-switch fault in the three-level NPC active rectifier causes a distortion in the input phase current and a ripple in the DC-link capacitor voltage. Therefore, proper fault diagnosis and tolerant control methods are required to prevent additional failures and performance degradation in the rectifier system. This paper conducted a detailed analysis of the effect of the single open-switch fault on the NPC PWM active rectifier and proposed a fault diagnosis method utilizing the DC link voltage and the phase angle of the input grid voltage. Furthermore, this paper proposes a fault-tolerant control method to reduce the effect of the open-switch fault by compensating a distorted reference voltage. The effectiveness of the proposed fault diagnosis and tolerant control methods are verified through experimental results.

This paper identifies possible topological reconfigurability of a T-type inverter for direct torque controlled (DTC) induction motor drives when an open-switch fault occurs. In open-switch fault, inverter current path is different than normal path. This causes undesirable inverter switching states. Since DTC is based on a voltage vector selection criterion, open-switch fault causes ambiguous torque control. Analysis of DTC drive under two different inverter open-switch fault conditions viz. half-bridge and neutral-point switch fault are presented. The operation of the inverter in DTC mode against faults is achieved by simple topological reconfiguration. [ABSTRACT FROM PUBLISHER]

To improve the reliability of the matrix converter (MC), a fault diagnosis method to identify a single open-switch fault is proposed in this paper. The introduced fault diagnosis method is based on finite control set-model predictive control (FCS-MPC), which employs a time-discrete model of the MC topology and a cost function to select the best switching state for the next sampling period. The proposed fault diagnosis method is realized by monitoring the load currents and judging the switching state to locate the faulty switch. Compared to the conventional modulation strategies such as carrier-based modulation method, indirect space vector modulation, and optimum Alesina–Venturini, the FCS-MPC has known and unchanged switching state in a sampling period. It is simpler to diagnose the exact location of the open switch in MC with FCS-MPC. To achieve better quality of the output current under single open-switch fault conditions without any redundant hardware, a fault tolerant strategy based on predictive control is also studied. The fault tolerant strategy is to select the most appropriate switching state associated with the remaining normal switches of the MC. Experiment results are presented to show the feasibility and effectiveness of the proposed fault diagnosis method and fault tolerant strategy. [ABSTRACT FROM PUBLISHER]

The converter with a single-phase rectifier, a dc-link circuit and a three-phase inverter is widely applied in high-speed railway electrical traction drive system. The fault frequency of single-phase rectifier is higher than that of three-phase inverter. Thus, this paper presents a new and fast model-based approach for open-switch fault diagnosis of the single-phase pulse width modulation rectifier, based on the mixed logical dynamic model and residual generation. It requires no additional hardware but only some measurements and command signals which are available in control system. This diagnosis method is quite suitable for electrical traction application due to the fast diagnosis time, simple structure and high reliability. Experimental results confirm the effectiveness and accuracy of the proposed algorithm. It is shown that such diagnosis method can locate the faulty switch in a few milliseconds which is important to avoid catastrophic consequences. [ABSTRACT FROM AUTHOR]

A three-level converter is used as the power converters of wind turbine systems because of their advantages such as low-current total harmonic distortion, high efficiency, and low collector–emitter voltage. Interior permanent magnet synchronous generators (IPMSGs) have been chosen as the generator in wind turbine systems owing to their advantages of size and efficiency. In wind turbine systems consisting of the three-level converter and the IPMSG, fault-tolerant controls for an open-circuit fault of switches should be implemented to improve reliability. This paper focuses on the open-circuit fault of outer switches (Sx1 and Sx4) in three-level rectifiers (both neutral-point clamped and T-type) that are connected to the IPMSG. In addition, the effects of Sx1 and Sx4 open-circuit faults are analyzed, and based on this analysis, a tolerant control is proposed. The proposed tolerant control maintains normal operation with sinusoidal currents under the open-circuit fault of outer switches by adding a compensation value to the reference voltages. The effectiveness and performance of the proposed tolerant control are verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

Reverse matrix converters, which can step up voltages, are suitable for applications with source voltages that are lower than load voltages, such as generator systems. Reverse matrix converter topologies are advantageous because they do not require additional components to conventional matrix converters. In this paper, a detection method and a post-fault modulation strategy to operate a converter as close as possible to its desired normal operation under the open-switch fault condition in the rectifier stage are proposed. An open-switch fault in the rectifier stage of a reverse matrix converter causes current distortions and voltage ripples in the system. Therefore, fault-tolerant control for open-switch faults is required to improve the reliability of a system. The proposed strategy determines the appropriate switching stages from among the remaining healthy switches of the converter. This is done based on reference currents or voltages. The performance of the proposed strategy is experimentally verified. [ABSTRACT FROM AUTHOR]

Multilevel rectifier topologies are commonly used in wide-power range applications. The T-type rectifier topology, which is a three-level topology, has an advantage in terms of efficiency compared to a neutral-point clamped (NPC)-type topology. In applications using the T-type rectifier topology, improving reliability has gained increased attention recently. A tolerance control for T-type rectifiers is necessary to improve the reliability of applications. When an open fault of switches connected to the neutral-point occurs, the NPC-type rectifier cannot restore distorted input currents, on the other hand, the T-type rectifier can eliminate the input current distortion completely. In this paper, we report two studies: 1) a three-level switching-oriented tolerance control, which is advantageous in terms of efficiency, for the Sx2 and Sx3 open-switch faults of the T-type rectifier and 2) comparison of the proposed tolerance control with two existing tolerance controls. In particular, the current total harmonic distortion, dc-link voltage ripple, and switch losses of these tolerance controls are analyzed by using simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a fault identification and tolerant method for switched reluctance motor (SRM) drives. The reliability of a power transistor in a power converter is the source of most problems in several industrial applications. It is critical to correctly diagnosis the faults occurring in a drive system to avoid harmful accidents and to ensure continuity of operation. In this paper, two types of faults, namely, short- and open-circuit faults, are analyzed on the basis of the current patterns of the power transistors of SRM drives. A fault is detected when the measured amplitude of the current differs from that of the normal-state current. A fault-tolerant scheme is applied according to the type of fault. Simulations and experiments are performed on a 1.0-kW SRM drive. The results are presented to verify the validity of the proposed method. [ABSTRACT FROM PUBLISHER]

The T-type topology is a three-level topology that has an advantage in terms of its number of switching device and its efficiency when compared to the neutral-point clamped (NPC)-type topology. With the recent increase in the usage of the T-type topology, the interest in its reliability has also increased. Therefore, a tolerance control for a T-type rectifier is necessary to improve the reliability of applications when an open-switch fault occurs. NPC-type rectifiers cannot eliminate input current distortion completely. However, the T-type rectifier is able to restore distorted current. In this paper, a tolerance control for the Sx2 and Sx3 open-switch faults of a T-type rectifier is proposed where it is advantageous in terms of efficiency when compared with other tolerance controls. The performance of the proposed tolerance control is verified through simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a new diagnosis method of an open-switch fault and fault-tolerant control strategy for T-type three-level inverter systems. The location of the faulty switch can be identified by the average of the normalized phase current and the change of the neutral-point voltage. The proposed fault-tolerant strategy is explained by dividing into two cases: the faulty condition of half-bridge switches and neutral-point switches. The performance of the T-type inverter system improves considerably by the proposed fault-tolerant algorithm when a switch fails. The proposed method does not require additional components and complex calculations. Simulation and experimental results verify the feasibility of the proposed fault diagnosis and fault-tolerant control strategy. [ABSTRACT FROM AUTHOR]

Fast fault detection and reconfiguration of power converters is necessary in electrical drives to prevent further damage and to make the continuity of service possible. On the other hand, component minimized converters may provide the benefits of higher reliability and less volume and cost. In this paper, a new fault-tolerant converter topology is studied. This converter has five legs before the fault occurrence, and after fault detection the converter continues to function with four legs. A very fast fault detection and reconfiguration scheme is presented and studied. Simulations and experimental tests are performed to evaluate the structure requirements, the digital reconfigurable controller, and fault detection scheme. For experimental tests, the control and the fault detection and reconfiguration schemes are implemented on a single field-programmable gate array (FPGA) chip. Experimental and simulation results show the effectiveness of the proposed fault-tolerant topology and its FPGA-based control. [ABSTRACT FROM PUBLISHER]

This paper proposes a fault-detection method for an open-switch fault in the switches of grid-connected neutral-point-clamped inverter systems. The proposed method can not only detect the fault condition but also identify the location of the faulty switch. In the proposed method, which is designed by incorporating a simple switching control in the conventional method, the fault condition is detected on the basis of the radius of the Concordia current pattern, and the location of the faulty switch can be identified. By using the proposed method, it is possible to detect the open-switch fault and identify the faulty switch within two fundamental periods, without using additional sensors or performing complex calculations. Simulations and experiments are carried out to confirm the reliability of the proposed fault-detection method. [ABSTRACT FROM AUTHOR]

This paper proposes a fault-detection method for open-switch failures in hybrid active neutral-point-clamped (HANPC) rectifiers. The basic HANPC topology comprises two SiC-based metal-oxide-semiconductor field-effect transistors (MOSFETs) and four Si insulated-gate bipolar transistors (IGBTs). A three-phase rectifier system using the HANPC topology can produce higher efficiency and lower current harmonics. An open-switch fault in a HANPC rectifier can be a MOSFET or IGBT fault. In this work, faulty cases of six different switches are analyzed based on the current distortion in the stationary reference frame. Open faults in MOSFET switches cause immediate and remarkable current distortions, whereas, open faults in IGBT switches are difficult to detect using conventional methods. To detect an IGBT fault, the proposed detection method utilizes some of the reactive power in a certain period to make an important difference, using the direct-quadrant (dq)-axis current information derived from the three-phase current. Thus, the proposed detection method is based on three-phase current measurements and does not use additional hardware. By analyzing the individual characteristics of each switch failure, the failed switch can be located exactly. The effectiveness and feasibility of the proposed fault-detection method are verified through PSIM simulations and experimental results. [ABSTRACT FROM AUTHOR]