A New Fault-Tolerant Three-Level T-Type Converter for SRM Drives in EVs/HEVs

Multilevel inverters enhance system-level performance in traction motor drives. This paper presents a novel three-level asymmetric T-Type converter for switched reluctance motors (SRMs) that offers robust fault tolerance against multiple open-circuit faults. Compared to existing multilevel inverters, the proposed topology achieves higher average torque and reduced torque ripple under fault conditions by ensuring that the faulty phase continues contributing to torque production. The operating modes of the converter are defined, and a current chopping control scheme is introduced. Under normal operation, bidirectional current excitation ensures full utilization of switching devices and balanced heat dissipation. Additionally, two-switch conduction reduces power losses compared to conventional four-switch conduction counterparts. The proposed topology offers excellent fault-tolerance for multiple open-circuit faults. During open-circuit faults, the faulty phase transitions to unidirectional current excitation while maintaining three-level operation or reducing to two-level operation under multiple failures. The feasibility of the proposed fault-tolerant converter is validated through MATLAB simulations on a three-phase <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$12 / 8$</tex> SRM model.