Active Fault Current Mitigation With Multi-Phase Inverter and Windings for Resilience Against Short-Circuit Faults Between Adjacent Turns

Abstract

This paper presents an active fault mitigation technique in response to a short-circuit fault between adjacent turns in electric machines. The proposed technique is demonstrated using a six-phase inverter, differential mode chokes (DMCs), and a dual three-phase interleaved winding arrangement. With this arrangement, a short circuit fault between adjacent turns becomes a phase-to-phase fault. Thus, the fault current no longer circulates only inside the motor; instead, it passes through motor terminals and can easily be measured. Then, a fault current mitigation control loop (FCMCL) is added to the field oriented control (FOC) algorithm to adjust the voltages applied to the affected phases to reduce the fault current. When a fault current is detected, the FCMCL injects a zero-sequence voltage in one of the three-phase sets. Using this method, the fault current is reduced to less than 4% of the rated current, allowing the machine to continue its operation almost completely close to normal conditions in the presence of fault. This 4% is an order of magnitude smaller than the 42% achieved with the baseline passive implementation involving only DMCs and a three-phase inverter. Close agreement between simulation and experimental results validates the effectiveness and accuracy of the proposed method.