Fault-tolerant control strategy of the open-winding inverter for DC-biased vernier reluctance machines

This paper proposes a fault-tolerant control strategy of the open-winding inverter for dc-biased vernier reluctance machines (dc-biased VRMs), aiming to maintain the output capability after the open-circuit fault occurs in the inverter switches. DC-biased VRMs are with integrated winding current for both dc component for field excitation and ac component for torque generation. The torque generation is not associated with the current direction, making the full-bridge inverter be divided into two groups of devices. The proposed fault-tolerant control strategy is based on the regular full-bridge inverter for each open winding and can control the motor in the fault-tolerant mode with one group of devices. When an open-circuit fault of a device appears in the normal mode, the controller will switch to the fault-tolerant mode. After a short transient period, the motor will be able to work. Moreover, in the fault-tolerant mode, a pulsewidth modulation driving method is proposed to reduce the current ripple. The proposed method does not require any additional components, and the reliability of the drive control system with the open-winding inverter is improved. Experimental results verify the validity and feasibility of the proposed fault-tolerant control strategy.