Postfault Sensorless Control of Three-Phase SPMSM Based on Unified Model of Diode-Through Residual Current under Single-Phase IGBT Open-Circuit Fault

Sensorless control under open-circuit faults is challenging for classic three-phase half-bridge motor drives. This paper proposes a method that exploits the correlation between back-electromagnetic force (back-EMF) and diode-through residual current in the IGBT open-circuit phase. First, the residual current model is developed, followed by a sampling strategy that unifies the model under different speeds. Using this unified model, a phase back-EMF observer is designed, enabling accurate postfault estimation of rotor speed and position. Experimental validation demonstrates the effectiveness of the proposed method, achieving an estimation error of 0.3 radians under steady-state conditions and 0.5 radians during acceleration and deceleration.