Open-circuit fault-tolerant control strategy based on five-level power converter for SRM system

Switched reluctance motor power converters are prone to open-circuit faults because it need to withstand large voltages and currents. Due to the small number of traditional asymmetrical half bridge topology switches, it is difficult to carry out fault tolerant control when power converters has an open-circuit fault, resulting in larger output torque ripple. This paper presents a five-level power converter based on the traditional asymmetric half-bridge power converter. The five-level topology has more switching states and can work in multi-level mode. Based on the topology, different excitation and demagnetization voltages can be choose at different speeds. A fault-tolerance strategy is developed to decrease the influence of the open-circuit fault. The five-level power converter has four switches per phase, and two of them will be used in one of the operating mode. So the remaining two of the switches can be used for safe backup, enabling fault-tolerant control when an open-circuit occur. Since each phase of the five-level power converter proposed in this paper is independent of each other, a reasonable control strategy can be used to avoid the unbalance of the midpoint potential. Finally, the topology and fault-tolerant strategy proposed in this paper are verified by simulation and experiment.