Common-Phase-Based Reliable Commutation and Shutdown Strategy for Three-Phase Single-Stage Converters

Three-phase single-stage isolated ac–dc converters are popular alternatives to conventional two-stage systems owing to their high power density and integration. However, the matrix converter on the primary side requires a four-step commutation process. If commutation fails, capacitor short circuits or resonant current interruptions may occur, leading to overcurrent or device overvoltage stress. This letter proposes a common-phase commutation (CPC) strategy that utilizes the natural freewheeling path of the common phase to guide resonant current transitions. It avoids direct comparison between two phase voltages with similar magnitudes and is independent of current polarity. A microsecond-level reverse-voltage shutdown method based on the CPC strategy is also introduced, enabling fast and robust demagnetization of the resonant inductor and transformer under any current direction. Simulation and experimental results confirm its effectiveness in improving commutation reliability and ensuring safe converter shutdown.