Fabien Meinguet

Fault-Tolerant Operation of an Open-End Winding Five-Phase PMSM Drive With Short-Circuit Inverter Fault

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

A Method for Fault Detection and Isolation Based on the Processing of Multiple Diagnostic Indices: Application to Inverter Faults in AC Drives

A general method for fault detection and isolation (FDI) is proposed and applied to inverter faults in drives of electric vehicles (EVs). This method is based on a change detection algorithm, which allows multiple fault indices (FIs) to be combined to retrieve the most likely state of the drive. The drive topology under study is a six-leg inverter associated with a three-phase open-end winding machine. Due to the inherent fault-tolerant topology, the conventional FIs are no longer effective. Therefore, an analysis of simulations under faulty conditions leads to the derivation of suitable FIs. These are based on the envelope of the phase currents, as well as their instantaneous frequency. Specific operating conditions related to the EV environment are taken into account, such as the flux-weakening region and energy recovery. In these modes of operation, FDI can be affected by uncontrolled currents circulating through the free-wheeling diodes. Finally, the performances of the FDI scheme are evaluated under steady-state and nonstationary conditions through simulations and experimental results.

Control Strategies for Open-End Winding Drives Operating in the Flux-Weakening Region

This paper presents and compares control strategies for three-phase open-end winding drives operating in the flux-weakening region. A six-leg inverter with a single dc link is associated with the machine in order to use a single energy source. With this topology, the zero-sequence circuit has to be considered since the zero-sequence current can circulate in the windings. Therefore, conventional overmodulation strategies are not appropriate when the machine enters in the flux-weakening region. A few solutions dealing with the zero-sequence circuit have been proposed in the literature. They use a modified space vector modulation or a conventional modulation with additional voltage limitations. This paper describes the aforementioned strategies, and then, a new strategy is proposed. This new strategy takes into account the magnitudes and phase angles of the voltage harmonic components. This yields better voltage utilization in the dq frame. Furthermore, inverter saturation is avoided in the zero-sequence frame, and therefore, zero-sequence current control is maintained. Three methods are implemented on a test bed composed of a three-phase permanent-magnet synchronous machine, a six-leg inverter, and a hybrid digital signal processor /field-programmable gate array controller. Experimental results are presented and compared for all strategies. A performance analysis is conducted as regards the region of operation and the machine parameters.

An on-line method for stator fault detection in multi-phase PMSM drives

This paper deals with an on-line fault detection method for multi-phase PMSM drives. The method is based on the detection of the stator current positive- and negative sequence fundamental components expressed in the stationary αβ reference frame. These components allow calculating a fault index used for the detection of stator faults, such as open-circuit faults. The decision criterion is based on the CUSUM algorithm. A model of a five-phase machine with one single-phase open-circuit is derived and validated with experimental results. Then, it is shown that the proposed method achieves fault detection on a wide speed range and even during speed transient.

Control strategies and reconfiguration of four-leg inverter PMSM drives in case of single-phase open-circuit faults

This paper deals with control strategies and reconfiguration needed to maintain PMSM drives in operation after a fault leading to a single-phase open circuit has occurred. The considered drive is composed of a three-phase star-connected machine and a four-leg voltage-source inverter, the fourth leg being permanently connected to the neutral point of the machine. We investigate different current and voltage control methods: hysteresis control in the abcn natural reference frame and in the dq0 synchronous reference frame and PI control in the dq0 synchronous reference frame. The methods are compared considering as criteria: the ease of implementation and reconfiguration and the performance before and after a fault such as the value of the torque ripple, the behaviour during transients and robustness against parameter variation.

Fault detection, isolation and control reconfiguration of three-phase PMSM drives

This paper deals with on-line software fault detection and isolation method for a drive composed of a fourleg inverter and a three-phase permanent magnet synchronous machine. The considered faults are single-phase open-circuit and current sensor outage. The method is based on the monitoring of the abc currents with phase-locked loops and the ‘CUSUM’ algorithm for the decision system. The impact of the considered faults is examined: first, in case there is no modification of the control and then in case a control reconfiguration is performed taking into account the fault diagnosis. Closed-loop operation is performed before, during and after the fault. Experimental results show that the latter case allows maintaining the drive in safe operation.

Computation of optimal current references for flux-weakening of multi-phase synchronous machines

Multi-phase synchronous machines are more and more used in specific applications where high power density, low bus voltage, wide speed range and fault-tolerant capabilities are required. Due to the high number of degrees of freedom, multi-phase machines are difficult to optimally operate in flux-weakening zones. This paper proposes a technique to numerically compute optimal current references that can be used for feed-forward flux-weakening techniques in order to exploit the maximum machine performances for given DC bus voltage and current limits. The proposed technique is applied to a five-phase permanent magnet synchronous machine specifically developed for an automotive application.

Different virtual stator winding configurations of open-end winding five-phase PM machines for wide speed range without flux weakening operation

This paper presents a specific control strategy of double-ended inverter system for wide-speed range of open-end winding five phase PM machines. Different virtual winding configurations (star, pentagon, pentacle and bipolar) can be obtained by choosing the appropriated switching sequences of two inverters. The motors speed range is thus increased.

Enhanced control of a PMSM supplied by a four-leg voltage source inverter using the homopolar torque

This paper investigates an electrical drive composed of a four-leg voltage source inverter and a three-phase star-connected surface permanent magnet synchronous machine. The fourth leg of the inverter is clamped to the neutral point of the machine. We find the current references leading to smooth torque and maximum torque per ampere operation in the presence of a third harmonic electromotive force component. We further analyze the advantages of the proposed topology in terms of torque increase and dc-link voltage requirements. Design aspects are briefly discussed.

Current sensor fault detection and isolation combining model-based and signal-based algorithms in PMSG drives

This paper presents a new on-line open-phase and current-sensor fault detection and isolation method for permanent-magnet synchronous generator (PMSG) drives with neutral point voltage control. Simple signal processing implementations for sensor outage and open-phase faults detection are combined with a cumulative-sum (CUSUM) algorithm capable of detecting smaller sensor output errors (offset or gain variation). The algorithm uses output signals from eight current sensors (two on each phase and two on the neutral wire). Experimental tests have been done on a 2kW-PMSG at different speeds and braking torques where different sensor-fault combinations have been tested with and without open-phase fault. Finally a test has been done while the shaft speed and the torque were varying in order to test the ability of the algorithm to work in transient conditions. Results show that the algorithm allows 3-out-of-6 redundancy in case of sensor outage and 5-out-of-6 redundancy in case of sensor offset or gain change with globally limited computational cost. Combinations of two outages and one offset or gain error can be isolated. In case of open-phase fault the algorithm can continue to detect sensor faults if at least one sensor is working on each remaining phase and on the neutral. A short fault detection time is obtained in case of sensor outage with a transitional detection by the CUSUM algorithm followed by the final detection by the signal processing algorithm.