Switch Open-circuit Faults Research Articles

Diagnosis of Multiple Open-Circuit Switch Faults Based on Long Short-Term Memory Network for DFIG-Based Wind Turbine Systems

Effective fault diagnosis for power electronic converters is an essential and mandatory operation to reduce failures and unscheduled shutdowns. This paper presents a data-driven fault diagnosis method, using long short-term memory (LSTM) network, to detect multiple open-circuit switch faults of the back-to-back converter in doubly fed induction generator (DFIG)-based wind turbine systems. Twelve sensor signals of the back-to-back converter for different fault types are measured. Wind speed fluctuation and sensor bias faults are considered as interference factors. The method has been evaluated in a grid-connected DFIG simulink model. Simulation results have demonstrated that, compared with least squares support vector machine (LS-SVM), back-propagation artificial neural network (BPANN) and recurrent neural network (RNN), the proposed method excavates the deep information of the fault signal with the highest diagnosis accuracy and strongest robustness with short time delay. Experimental tests undertaken on a hardware-in-the-loop testing platform further validate the effectiveness of the LSTM-based network.

Detection and identification of multiple IGBT open‐circuit faults in PWM inverters for AC machine drives

This study proposes a new scheme for online detection and identification of single and multiple insulated-gate bipolar transistor (IGBT) open-circuit faults in three-phase pulse-width modulation (PWM) inverters of AC machine drives, which is based on Park's vector of machine phase currents. First, the switch open-circuit faults are detected by monitoring dwell times of the vector of the actual phase currents expressed in the stationary reference frame in each sector, where the normalisation of the current to its reference value is utilised, by which the immunity to the false alarms in transient conditions is improved significantly. Then, the IGBT open-circuit faults are identified, where leg open-circuit conditions are in the first place determined based on the average values of the normalised line-to-line currents. Next, the single open-circuit IGBT is located from the polarity of the corresponding phase current. By the proposed diagnosis method, the fault detection time is at the longest about 52.3 and 54% of a fundamental period in the simulation and experimental tests, respectively, and the 27 possible cases of IGBT open-circuit faults combined for all IGBTs in the inverter can be identified. In addition, this algorithm can be implemented without any additional hardware and computational burden.

Fault‐tolerant control of DSBLDC motor drive under open‐circuit faults

Doubly salient brushless dc (DSBLDC) motor drive system has attracted increasing attention due to the rugged rotor structure, brushless operation and low cost. The switch open-circuit (OC) fault increases the torque ripple and decreases the maximal output power of DSBLDC motor drive system. A fault-tolerance control strategy for switch OC circuit is proposed in this study. The back electromotive force (BEMF) current would occur in a pulse-width modulation (PWM) pattern. It severely degrades the proposed method's fault-tolerant performance. So the cause of the BEMF current is analysed and BEMF current is suppressed by specific PWM pattern. Finally, the fault-tolerance control strategy is verified by experiment results and the selection PWM pattern is proved to be correct and practical.

Common Switch Fault Diagnosis for Two-Stage DC-DC Converters Used in Energy Harvesting Applications

This paper proposes a new Unified Switch Fault Diagnosis (UFD) approach for two-stage non-isolated DC-DC converters used in energy harvesting applications. The proposed UFD is compared with a switch fault diagnosis consisting of two separate fault detection algorithms, working in parallel for each converter. The proposed UFD is simpler than the two parallel fault diagnosis methods in realization. Moreover, it can detect both types of switch failures, open circuit and short circuit switch faults. It can also be used for any two-stage non-isolated DC-DC converters based on two single switch converters, no matter the converter circuits in each stage. Some selected simulation and Hardware-in-the-Loop (HIL) experimentation results confirm the validity and efficiency of the proposed UFD. Also, the proposed UFD is applied successfully for fault-tolerant operation of a buck/buck–boost two-stage converter with synchronous control and a redundant switch.

Modular Full-Bridge Converter for Three-Phase Switched Reluctance Motors With Integrated Fault-Tolerance Capability

In this paper, a novel modular full-bridge converter is proposed for three-phase switched reluctance motors (SRMs), which provides an advanced fault-tolerance solution for both the open- and short-circuit faults in switching devices. The proposed converter is composed of two standard six-pack switch modules, providing great benefits for industrial massive production due to the modular topology. Under normal conditions, bidirectional current excitation is developed in the proposed converter, where all the switching devices are actively involved, which makes full use of the switches and averages the heat dissipation for the heat sink design. When a switch fault occurs, the fault signature can be extracted by detecting the characteristics of phase currents and operation modes, and effective fault-tolerance strategies are further applied to achieve the fault-tolerance operation accordingly. Under switch open-circuit faults, the faulty phase is adjusted to unidirectional current excitation without degrading the motor performance. Under switch short-circuit faults, the motor can still work steadily with a single six-switch inverter module by easily reconstructing the proposed converter, without losing any phase windings. The simulation and experiments on a three-phase 12/8 SRM are carried out to validate the feasibility of the proposed converter and control techniques.

A new approach for on-line open-circuit fault diagnosis of inverters based on current trajectory

Security and reliability of inverter are an indispensable part in power electronic system. Faults of inverter are usually caused by switch elements’ operating fault. Taking the inverter with hysteresis current control as the research object, a universal open-circuit fault location method which can be applied to multiple control strategies is proposed in the paper. If the switch open-circuit fault happens in inverter, the output phase current will inevitably change, which can be used as a characteristic for diagnosis, combined with the comparison of phase-current direction before and after the fault occurrence, to diagnose and locate the open-circuit fault in a half cycle. Moreover, this method requires neither system control signals nor sensor. The validity, reliability and limitation of the fault location method in the paper are verified and analyzed through dSPACE-based experiment platform.

Approach to synthesis of fault tolerant reduced device count multilevel inverters (FT RDC MLIs)

Multilevel inverters (MLIs) are rapidly acquiring techno-economic feasibility for both high-power and medium-power applications. Increased number of power switches has been cited as one of the most important limitations of MLIs; and to overcome it, a whole new class of MLI topologies has come up. These topologies are commonly called `reduced device count' MLIs (RDC-MLIs). As the number of controlled switches is significantly reduced in RDC-MLIs, the redundant states are also reduced. Hence, the possibility of fault tolerant operation is severely affected. This study looks at the possibility of imparting fault-tolerant characteristics to RDC-MLIs. In this study, some of the recently proposed RDC-MLI topologies are first analysed for the possibility of fault tolerant operation in the case of `any single switch open-circuit fault (ASSOF)'. Thereafter, an optimal addition of power switch is proposed which enables fault tolerant operation in the event of ASSOF. Furthermore, these modified RDC-MLIs are verified under normal and faulty conditions using software simulations and experimental set-ups and these results are presented.

A Noninvasive and Robust Diagnostic Method for Open-Circuit Faults of Three-Level Inverters

This paper proposes a noninvasive switch open-circuit (OC) fault diagnosis method for a three-level inverter based on voltage detection. Under both healthy and faulty operation, the possible values of two line voltages are analyzed, and the waveforms are obtained according to the analysis. Faults can be quickly diagnosed by the ratio, the voltage difference, and the arithmetic values of the two line-voltages. The time consumption of the single-switch OC faults diagnosis is less than half of a cycle. When some of two switches failures (double-switch OC faults) occur, faults can also be accurately located using this method, and these fault diagnosis processes can be completed within one cycle. Performance evaluation experiments are carried out to verify the effectiveness of the method. The results show that the proposed method is robust to load variation and immune to certain load OC failures. It was also found in the experiments that the diode OC faults can be distinguished from switch OC faults despite having similar fault features.

Matrix Converter Open-Circuit Fault Behavior Analysis and Diagnosis With a Model Predictive Control Strategy

A novel fast and reliable open-circuit fault diagnosis strategy for a matrix converter with a finite-control-set model predictive control strategy is proposed in this paper. Current sensors are located ahead of the clamp circuit to measure the output currents in order to improve the speed of fault diagnosis. In addition, the current recirculating path during a single open-circuit switch fault condition is given in detail with the aim of contributing more expert knowledge to the fault diagnosis. The proposed fault diagnosis method is applicable over the whole range of modulation index.

Discrete and Parametric Fault Diagnosis of an Inverter-Driven Brushless DC Motor Using a Hybrid Formalism

This paper presents a diagnosis approach for inter-turn short circuit faults and open circuit switch faults in a brushless direct current (BLDC) motor driven by a three-phase voltage source inverter taking into account their hybrid behaviour. The diagnosis method consists of a discrete faults diagnosis module and a continuous faults diagnosis module combined by means of a hybrid automaton. The discrete diagnoser constitutes the discrete part of the hybrid automaton. It is designed based on a discrete presentation of the system taking into consideration the nominal and faulty states. On the other hand, continuous fault diagnosis is achieved by a hybrid sliding mode observer based on the Super Twisting algorithm. A Lyapunov based approach is used to address the convergence analysis problem of the hybrid observer. The performance of the proposed approach in detection and isolation of discrete and parametric faults is demonstrated by numerical simulations.

Seamless Fault-Tolerant Operation of a Modular Multilevel Converter With Switch Open-Circuit Fault Diagnosis in a Distributed Control Architecture

Modularity and high reliability from redundancy are the two attractive advantages of modular multilevel converters (MMCs). This paper elaborates a switch open-circuit fault diagnosis and a fault-tolerant operation scheme for MMCs with distributed control. The proposed fault diagnosis and fault-tolerant control method can significantly improve the reliability of the MMC while maintaining the modularity of its software implementation. By distributing fault diagnosis into submodules, its local controller is capable of identifying the switching devices in open-circuit fault without extra hardware circuitry. Based on the real-time measurements of submodule terminal voltage and arm current, single, or multiple faulty switches can be identified within 3.5 ms without triggering faulty alarms. Furthermore, a new fault-tolerant operation is proposed to maintain the output current, internal dynamics, and switching harmonics unchanged after the faulty submodule is bypassed. This is achieved by resetting the period and phase registers in the local controller according to the information of bypassed submodules. The control loops of the MMC are not influenced by the proposed fault diagnosis and fault-tolerant operation, making the operation transition seamless and reliable. Experimental results show that fault identification and system reconfiguration can be completed within 5 ms, and the MMC can seamlessly and smooth ride through the switch open-circuit faults without severe malfunction and catastrophic damages.

An Advanced Three-Level Active Neutral-Point-Clamped Converter With Improved Fault-Tolerant Capabilities

A resilient fault-tolerant silicon carbide (SiC) three-level power converter topology is introduced based on the traditional active neutral-point-clamped converter. This novel converter topology incorporates a redundant leg to provide fault tolerance during switch open-circuit faults and short-circuit faults. Additionally, the topology is capable of maintaining full output voltage and maximum modulation index in the presence of switch open and short-circuit faults. Moreover, the redundant leg can be employed to share load current with other phase legs to balance thermal stress among semiconductor switches during normal operation. A 25-kW prototype of the novel topology was designed and constructed utilizing 1.2-kV SiC metal–oxide–semiconductor field-effect transistors. Experimental results confirm the anticipated theoretical capabilities of this new three-level converter topology.

Switch fault detection and diagnosis in space vector modulated cascaded H-bridge multilevel inverter

ABSTRACTThis article investigates the development and online implementation of the power switch open-circuit fault detection and diagnosis in symmetric cascaded H-bridge multilevel inverter. A mathematical modelling technique is presented to understand the effect of the fault on the bridge voltages and output voltage. The modelled values of the output voltage, simulation results and experimental results indicate that the fault diagnostic methods based on the output voltage as the diagnostic feature have certain ambiguity in identifying the fault switch, since the output voltage waveform and its features remain the same for a group of switches under the fault condition. In order to overcome this, fault detection and diagnosis method based on the mean values of the bridge voltages is proposed in this article, which identifies the faulty switch pair and H-bridge in which the fault has occurred. Further, this method has been experimentally validated on a five-level space vector modulated symmetric cascaded H-bridge multilevel inverter.

Comprehensive Investigation on Remedial Operation of Switch Faults for Dual Three-Phase PMSM Drives Fed by T-3L Inverters

In this paper, the remedial operation of switch faults will be investigated comprehensively for T-type-three-level-inverter-fed dual three-phase motor drives. The open-circuit switch faults in multiple phase legs are discussed at first. The faulty conditions are classified into five categories. Different remedial strategies, namely Type-I to Type-V schemes, are proposed for different faulty conditions. In particular, three kinds of Type-III fault-tolerant control schemes are proposed by using medium-voltage vectors to synthesize small-voltage vectors, in such a way that the mid-point voltage in a dc link can be stabilized well. Then, the short-circuit faults in both clamping switches and half-bridge switches are investigated. By analysis, their operation conditions are equivalent to conditions loss of both P and N voltage levels and open-phase faults, respectively. Thus, the corresponding remedial strategies can be applied accordingly. Particularly, a voltage compensation control method is proposed for conditions, where open-switch faults coexist with open-phase operation induced by short-circuit faults in half-bridge switches. The validity of all of theoretical analysis and the proposed remedial strategies has been verified by experiments.

Service Continuity of PV Synchronous Buck/Buck-Boost Converter with Energy Storage†

Numerous advantages offered by Photovoltaic (PV) generation systems coupled with the increasing power demands for clean energy put PV systems in the front of many research works. For stand-alone applications powered with PV systems, the reliability of the power conversion stage is essential to ensure the continuous supply of energy. Therefore, in the case of any failure occurring in the power conversion stage, it is mandatory to provide remedial actions to guarantee the service continuity of the produced electrical power. This paper analyses the service continuity of a two-stage buck/buck-boost converter with energy storage, driven with synchronous control. The initial two-stage converter is made fault-tolerant and robust to failures of its two switches by adding only one additional switch associated with two diodes. In this study, only open-circuit switch faults are considered. The proposed fault-tolerant circuit and the initial one have the same electrical behavior when synchronous control is used. The applied synchronous control in both healthy conditions and post-fault operation ensures the same functionalities without degrading the system’s performances. The proposed two-stage synchronously-controlled circuit is validated through simulation in the cases of open circuit faults on the two switches of the initial converter. The obtained results show the feasibility of the proposed functional redundancy and the continuity of operation at full power after switch fault diagnosis.

Post-Fault Operation Strategy for Single Switch Open-Circuit Faults in Electric Drives

Single switch open-circuit faults in three-phase ac drives lead to undesired effects and potentially to a total failure of the drive. This paper proposes a postfault operation strategy for such faults with a focus on the limitation of losses after the reconfiguration and thereby an extension of the possible range of operation. Furthermore, a method for the reduction of alternating torque components during the postfault operation of a squirrel cage induction machine drive is proposed. The performance of the postfault operation strategy and the alternating torque reduction method are shown both via simulations and experiments.

Influence of direct‐connected inverter with one power switch open circuit fault on electromagnetic field and temperature field of permanent magnet synchronous motor

For permanent magnetic motors, the faults in inverter may cause serious mechanical vibration, winding overheating, and thermal demagnetisation for the magnets. Thus, this study addresses the problem of the electromagnetic field and temperature distributions for permanent magnet synchronous motor (PMSM) under open circuit fault (OCF) in the upper switch of one phase. Firstly, taking a 12.5 kW 2000 r/min PMSM as an example, the 2D transient electromagnetic field-circuit coupling calculation model is established. Then the flowing paths of the three-phase currents in inverter are analysed before and after the OCF in the upper switch of one phase. Next, by using the finite-element method, the current harmonics, the electromagnetic torque, the rotating speed, and the losses in PMSM are investigated. Simultaneously, direct current component and torque pulsation are also derived. Based on the 3D temperature field, the temperature distributions in different parts of PMSM also are comparatively studied before and after this fault. Moreover, the temperature of permanent magnets, which is the part most seriously affected by the temperature, are further analysed. Finally, calculation and experimental tests prove the accuracy of the theoretical analysis. The obtained conclusions may provide some references for the limit operation and effective diagnosis for inverter faults.

Detection of Two-Level Inverter Open-Circuit Fault Using a Combined DWT-NN Approach

Three-phase static converters with voltage structure are widely used in many industrial systems. In order to prevent the propagation of the fault to other components of the system and ensure continuity of service in the event of a failure of the converter, efficient and rapid methods of detection and localization must be implemented. This paper work addresses a diagnostic technique based on the discrete wavelet transform (DWT) algorithm and the approach of neural network (NN), for the detection of an inverter IGBT open-circuit switch fault. To illustrate the merits of the technique and validate the results, experimental tests are conducted using a built voltage inverter fed induction motor. The inverter is controlled by the SVM control strategy.

Open- and Short-Circuit Fault Identification for a Boost dc/dc Converter in PV MPPT Systems

This paper proposes a fault identification system for short and open-circuit switch faults (SOCSF) for a dc/dc converter acting as a Maximum Power Point Tracker (MPPT) in Photovoltaic (PV) systems. A closed-loop operation is assumed for the boost dc/dc converter. A linearizing control plus a Proportional-Derivative (PD) controller is suggested for PV voltage regulation at the maximum power point (MPP). In this study, the SOCSF are modeled by using an additive fault representation and the fault identification (FI) system is synthesized departing from a Luenberger observer. Hence, an FI signal is obtained, which is insensitive to irradiance and load current changes, but affected by the SOCSF. For FI purposes, only the sensors used in the control system are needed. Finally, an experimental evaluation is presented by using a solar array simulator dc power supply and a boost dc/dc converter of 175 W in order to validate the ideas this study exposes.

Low‐cost post power switch open‐circuit fault operation approach for an IPMSM drive

This study proposes an approach for the fault-tolerant control of an interior permanent magnet synchronous motor (IPMSM) drive when a power switch open-circuit fault occurs without addition of any extra hardware or reconfiguration to the inverter. With this approach, the IPMSM's operation effectively alternates between the three-phase mode and the two-phase mode. Thus, the electric power is evenly distributed between three-phase windings as much as possible, and the remaining healthy power devices are all utilised. The post-fault drive performance is analysed. A simulation model has been built to verify the proposed principle. Finally, the approach has been implemented on an IPMSM test rig. Both the simulation and experimental results confirm the feasibility of the method.