Two-step commutation for Isolated DC-AC Converter with Matrix Converter

This paper proposes a two-step commutation method for a three-phase-to-single-phase matrix converter. Conventional two-step commutation cannot be applied at all operation regions because a commutation failure due to the detection error of grid voltages still occurs. In the proposed two-step commutation, by modulating only one of two devices in a bi-directional switch and utilizing a zero vector to let the switches naturally turn-off, the commutation failures are avoided completely regardless of the voltage detection error. From experimental results, it is confirmed that the proposed two-step commutation has always safety operation to avoid commutation failure. The input current THD at 10 kW with the proposed two-step commutation is improved by 37% in comparison with the conventional four-step commutation.