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.

This paper deals with easy-to-implement control strategies when a seven-phase axial flux permanent magnet machine supplied by a seven-leg voltage source inverter is in fault operation mode. Using a vectorial multimachine description, a seven-phase machine presenting a heightened ability to be controlled with one or two open-circuited phases has been designed. The machine is first presented, and experimental results are provided when one or two phases are open circuited. Based on a vectorial approach, new current references are calculated to avoid high-torque ripples.

This paper deals with the generation of optimal current references for multiphase permanent-magnet (PM) synchronous machines in normal or fault mode (open-circuited phases). Current references are computed in order to keep a constant torque while minimizing instantaneous joule losses. In comparison with commonly used scalar methods, a vectorial approach makes it possible to reduce the number of computations in order to generate optimal current references in real time. In addition to this, since current references are expressed in terms of physical parameters of the machine, this approach can be used to evaluate the influence of machine parameters over the control performances. Finally, experimental results of a surface-mounted PM five-phase synchronous machine are provided in order to demonstrate the proposed strategy.

A generic and simple control method is suggested for any multileg voltage-source-converter. A specific coding yields an inversion table allowing a fast practical implementation. Phase-to-phase voltage references have to be defined for such a table. This original control strategy is validated by experimental results for two-leg, three-leg, four-leg, and five-leg structures supplying balanced and unbalanced multiphase loads.

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.

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.