With wide-spread application of power electronic systems across many different industries, their reliability is being studied extensively. This paper presents a comprehensive review of reliability assessment and improvement of power electronic systems from three levels: 1) metrics and methodologies of reliability assessment of existing system; 2) reliability improvement of existing system by means of algorithmic solutions without change of the hardware; and 3) reliability-oriented design solutions that are based on fault-tolerant operation of the overall systems. The intent of this review is to provide a clear picture of the landscape of reliability research in power electronics. The limitations of the current research have been identified and the direction for future research is suggested.

https://www.egr.msu.edu/~bingsen/files_publications/J-13_TPEL_Reliability.pdf

Survey on Reliability of Power Electronic Systems

Power electronics plays an important role in a wide range of applications in order to achieve high efficiency and performance. Increasing efforts are being made to improve the reliability of power electronics systems to ensure compliance with more stringent constraints on cost, safety, and availability in different applications. This paper presents an overview of the major failure mechanisms of IGBT modules and their handling methods in power converter systems improving reliability. The major failure mechanisms of IGBT modules are presented first, and methods for predicting lifetime and estimating the junction temperature of IGBT modules are then discussed. Subsequently, different methods for detecting open- and short-circuit faults are presented. Finally, fault-tolerant strategies for improving the reliability of power electronic systems under field operation are explained and compared in terms of performance and cost.

Study and Handling Methods of Power IGBT Module Failures in Power Electronic Converter Systems

With wide-spread application of power electronic converters in high power systems, there has been a growing interest in system reliability analysis and fault-tolerant capabilities. This paper presents a comprehensive review of conventional fault-tolerant techniques regarding power electronic converters in case of power semiconductor device failures. These techniques can be classified into four categories based on the type of hardware redundancy unit: switch-level, leg-level, module-level, and system-level. Also, various fault-tolerant methods are assessed according to cost, complexity, performance, etc. The intent of this review is to provide a detailed picture regarding the current landscape of research in power electronic fault-handling mechanisms.

Survey on Fault-Tolerant Techniques for Power Electronic Converters

Inverters play key roles in motor drives, flexible power transmissions, and recently grid-tied renewable energy generation units. Therefore, availability and reliability of inverters have become increasingly important. Following early stage fault detections in inverters, remedial actions can extend normal operation of inverters and, in some cases, derate the system to prevent unexpected shutdowns. A remedial action typically contains a combination of hardware and software reconfigurations. The main purpose of this paper is to provide an instructive survey of existing fault-tolerance (remedial) techniques for three-phase, two-level, and multilevel inverters.

Survey of Fault-Tolerance Techniques for Three-Phase Voltage Source Inverters

Three-phase inverters are currently utilized in an enormous variety of industrial applications, including variable-speed ac drives. However, due to their complexity and exposure to several stresses, they are prone to suffer critical failures. Accordingly, this paper presents a novel diagnostic algorithm that allows the real-time detection and localization of multiple power switch open-circuit faults in inverter-fed ac motor drives. The proposed method is quite simple and just requires the measured motor phase currents and their corresponding reference signals, already available from the main control system, therefore avoiding the use of additional sensors and hardware. Several experimental results using a vector-controlled permanent-magnet synchronous motor drive are presented, showing the diagnostic algorithm effectiveness, its relatively fast detection time, and its robustness against false alarms.

A New Algorithm for Real-Time Multiple Open-Circuit Fault Diagnosis in Voltage-Fed PWM Motor Drives by the Reference Current Errors

A novel fast-diagnostic method for open-switch faults in inverters without sensors is proposed to improve the reliability of power electronic system in this paper. The presented method is achieved by analysis of switching function model of the inverter under both healthy and faulty conditions. Due to the different voltages endured by each power switch under healthy condition from open-switch faults in some cases, open-circuit faults can be detected by sensing the collector-emitter voltages of the lower power switches in each leg. The diagnostic scheme employs the simple hardware circuit to obtain indirectly the voltages of lower power switches and to get rid of high cost and complexity as a result of sensors. Also, this method minimizes the detection time and is available for the inverter faults in the systems with open-loop or closed-loop current control strategies. To ensure the effectiveness and reliability of the proposed diagnostic method, the rising-edge delays for switching signals are used to avoid misdiagnostic results because of the ON-OFF processes of power switches, and the delay durations are determined considering various factors. Simulation and experimental results validate the proposed scheme for detecting switch and leg open-circuit faults.

Switching Function Model-Based Fast-Diagnostic Method of Open-Switch Faults in Inverters Without Sensors

This paper proposes a dual-space vector control scheme for the open-end winding permanent magnet synchronous motor (OEW-PMSM) drive fed by the dual inverter with a single dc supply. Potential zero-sequence current in the open-end winding drive system has to be considered since it causes circulating current in the winding and leads to high current stress of power semiconductor devices and high losses. Zero-sequence current in open-end winding ac motor drives is usually caused by the zero-sequence voltage, and therefore switching combinations which do not produce zero-sequence voltage are used to synthesize the reference voltage in existing methods. But even so, the zero-sequence voltage can also be produced by the dead time of the inverter. In order to suppress zero-sequence current in the OEW-PMSM drive, a dual-space vector control scheme is proposed and a novel dual-inverter space vector pulse width modulation (PWM) with the zero-sequence voltage reference is employed to regulate system zero-sequence voltage in this paper. Compared with existing dual inverter PWM strategies, the novel algorithm build a regulation mechanism for the zero-sequence voltage. The proposed method is compared with the conventional vector control by simulations and experiments, and the results shown that the proposed scheme can suppress zero-sequence current effectively.

Dual-Space Vector Control of Open-End Winding Permanent Magnet Synchronous Motor Drive Fed by Dual Inverter

This paper presents an open-circuit (OC) fault diagnostic method of inverters in closed-loop controlled permanent magnet synchronous motor drive systems based on current residual vector (CRV). This method can get rid of effects of the load and the main controller to obtain reliable detection. The motor drive system is a hybrid system composed of discrete switching signal events and continuous current state variables, which evolves in certain law driven by discrete events. At the base of analyzing operation modes of the system, a mixed logical dynamic (MLD) model of the motor drive system is built to estimate motor currents. Consequently, the proposed fault diagnostic scheme is constructed by the healthy current estimator based on the MLD model in parallel with the plant. When an OC fault occurs, the CRV between the estimator and the plant will show featured amplitude and phase, and hence the fault can be detected. The method utilizes variables already used by the main controller, avoiding the use of extra sensors. During the implementation, amplitude threshold and phase sector are used in order to avoid effects of measurement errors, model parameter errors and noises, which improves the reliability and robustness. Simulation and experimental results validate the proposed diagnostic method, and the diagnostic duration can be reduced within a quarter of fundamental wave period.

Current Residual Vector-Based Open-Switch Fault Diagnosis of Inverters in PMSM Drive Systems

Fault-tolerant control of a five-phase (5Ph) permanent magnet (PM) motor has been recently widely studied, however decoupled modeling under faulty conditions is discussed in less details. In this paper, decoupled model of the 5Ph PM motor under single-phase open fault is investigated and based on the proposed model field oriented control (FOC) is applied to the motor. The proposed model is based on the concept of preserving values of fundamental magnetic motive force (MMF) and back electromotive force (EMF) under single-phase open fault, the same as in healthy case, along with keeping equal torque equation at fundamental rotating space. Nevertheless, the output torque still presents some noises due to third harmonics of air-gap flux and system uncertainties, and to cope with those disturbances, sliding mode control (SMC) is proposed in the speed loop to improve the speed performance. The proposed SMC contains a PI controller and a chattering term, and thus it can be easily tuned. The decoupled model is verified by transient finite element analysis finite element analysis (FEA) and further experiment results are presented to confirm the effectiveness of the proposed control strategy.

Decoupled Modeling and Nonlinear Speed Control for Five-Phase PM Motor Under Single-Phase Open Fault

This paper presents a new harmonic current excitation principle for a synchronous machine drive based on control of the spatial third harmonic MMF. Unlike existing harmonic excitation technologies, which utilize the third harmonic components of the rotor magnetic field, this brushless harmonic excitation principle is realized by injecting an ac single-phase current component or dc component into three-phase open stator windings thereby utilizing the resultant third harmonic spatial stator MMF component. This additional component generates either a stationary or time pulsating magnetic field which will induce voltages in a specially designed rotor winding. Through rectification, the induced voltage is used to supply dc current to the rotor excitation winding. To verify the aforementioned principle, theoretical analyses, magnetic field calculations by finite-element analysis and experiments with a 1.0-kW prototype machine have been performed and key influential factors have been investigated. The test results are shown to be consistent with the theoretical analysis, which validates the correctness of the theory.

Quntao An

Papers

Switching Function Model-Based Fast-Diagnostic Method of Open-Switch Faults in Inverters Without Sensors

Dual-Space Vector Control of Open-End Winding Permanent Magnet Synchronous Motor Drive Fed by Dual Inverter

Current Residual Vector-Based Open-Switch Fault Diagnosis of Inverters in PMSM Drive Systems

Decoupled Modeling and Nonlinear Speed Control for Five-Phase PM Motor Under Single-Phase Open Fault

Principle of Operation and Performance of a Synchronous Machine Employing a New Harmonic Excitation Scheme