This paper investigates the open-circuit fault-tolerant current control for a five-phase fault-tolerant permanent-magnet (PM) machine used for electric vehicles. By relieving the common constraint of zero neutral point current in the existing fault-tolerant control strategies and reconfiguring the maximum round rotating magnetomotive force under different fault conditions, the new current sets, which enable the five-phase PM machine to output the maximum smooth torque, are obtained by the analytical method. Compared with the existing fault-tolerant control strategy, larger torque and lower torque ripple can be obtained with the proposed fault-tolerant control strategy, and the five-phase PM machine can safely operate with the loss of up to three phase windings. The proposed fault-tolerant control strategy is verified by both finite-element analysis and experimental results. The developed fault-tolerant current control strategy can be generalized into any multiphase PM machines.

In this paper, a six-phase fault-tolerant modular permanent magnet synchronous machine (PMSM) with a novel 24-slot/14-pole combination is proposed as a high-performance actuator for wheel-driving electric vehicle (EV) applications. Feasible slot/pole combinations of the fractional-slot concentrated winding six-phase PMSM are elicited and analyzed for scheme selection. The novel 24-slot/14-pole combination is derived from the analysis and suppression of the magnetomotive force (MMF) harmonics. By making use of alternate-teeth-wound concentrated winding configuration, two adjacent coils per phase and unequal teeth widths, the phase windings of the proposed machine is magnetically, thermally isolated, which offers potentials of modular design and fault tolerant capability. Taking advantage of the leakage component of winding inductance, 1.0 per unit short-circuit current is achieved endowing the machine with short-circuit proof capability. Optimal design of essential parameters aiming at low eddy current losses, high winding factor and short-circuit-proof ability are presented to pave the way for a high-quality system implementation.

The multiphase machine is a competitive candidate for applications where uninterrupted operation is demanded under post-fault conditions. In this paper, the decoupling vector control for a surface mounted five-phase permanent-magnet (PM) synchronous machine (PMSM) under single-phase open-circuit fault is investigated. The decoupled mathematical model of the five-phase PMSM under single-phase open-circuit fault is derived. Then, two post-fault control strategies are obtained, which are based on the principles of minimum copper loss and equal amplitudes of currents, respectively. The post-fault control strategy based on the feed-forward compensation is proposed in order to eliminate the influences of certain factors and decrease the current ripple. The validity of the post-fault control strategies is proved by experiments.

The hybrid variable-flux permanent-magnet synchronous machine (VF-PMSM) is an alternative candidate for adjustable speed applications. The series magnet and parallel magnet configurations are the two existing topologies for hybrid VF-PMSMs. However, they both have drawbacks that have not been fully resolved. A premium topology with high power density and magnetization regulation using acceptable current pulses is highly desired. This paper proposes a new hybrid VF-PMSM with a quasi-series magnet configuration and a passive flux barrier. After introducing the proposed topology and its operating principles, the results of a comparative study are presented comparing the magnetization characteristics and torque capabilities of the three configurations. The influences of key design variables on the machine’s performance are investigated, showing that the proposed machine can achieve a relatively high power density comparable to the series configuration, and the required magnetization current amplitude falls within acceptable limits.

This paper proposes a multiphase modular fault-tolerant permanent-magnet (PM) machine with hybrid single/double-layer fractional-slot concentrated winding (FSCW). Comparisons between the proposed machine and conventional FSCW machines are made to indicate the special characteristics in aspects of armature magnetomotive force harmonic distribution, cogging torque, magnetic isolation ability, and torque capability. Then, influences of specific structural parameters, including the angle between single-layer slot (SLS) and double-layer slot (DLS) and the opening widths of SLS and DLS, on machine performances are investigated, and power density of the machine is improved by selecting the parameters appropriately. In addition, two stator modular design schemes are proposed. The influences of gaps between modules on machine performances, such as torque, losses, inductances, and short-circuit current, are investigated.

Current-source inverter is considered as a promising candidate in the permanent-magnet synchronous machine drive system for its superior current waveforms and inherent capability of withstanding the short-circuit failure. However, the resonance issue is yielded, resulting from the paralleling of machine inductances and filter capacitors. Very limited control bandwidth can be retained if only considering the passive damping of winding resistance. In this article, the decoupled active damping current controller in the synchronous frame is investigated. The impedance analysis is performed to make a more intuitive demonstration on the damping mechanism, which reveals that the virtual impedance is not always linearly correlated with the damping gain. The digital delay is crucial for the accurate assessment on the damping effectiveness, and the z -domain discrete model is established to emulate the real circumstance. The quantified analysis is performed on deriving the stable boundaries of controller parameters. The frequency responses and root trajectories are illustrated to validate the conclusions. The optimized parameters are obtained by the proposed tuning procedure, which realizes a balance between the damping effect and the bandwidth performance. Finally, the experiments are performed to verify the proposed control schemes.