Research on two-step voltage-controlled commutation strategies for Matrix Converter

Reliable current commutation between switches in matrix converters is more difficult to achieve than in conventional voltage-source inverters since there are no natural freewheeling paths. Based on analyzing the causes of input phase voltage short circuit in the critical situation, an improved method for two-step voltage commutation strategy is proposed in this paper. By using the critical intervals, defining new commutation steady states (P, M, N) and new commutation intermediate states (PM, MN, NP), selecting special zero vectors and changing sequence of vectors, the short circuit phenomenon in the critical intervals can be avoided. The method has little influence on input currents and output voltages. Experimental results of a 5 kW matrix converter prototype verify the validity and feasibility of the safe commutation method. The power equipment need not precise circuit to detect the polarity of input line voltage and the control circuit is easy to realize.