A Hybrid Common Mode Voltage Suppression Method for Matrix-Type Back-to-Back Converter

The matrix-type back-to-back converter (MTBBC) is a novel AC-AC converter topology with only 12 switches and no dc-link energy-storage elements. Like other AC-AC converters, the MTBBC suffers from the high common-mode voltage (CMV) due to the pulse width modulation (PWM), which results in problems such as motor bearing damage and winding failures. This paper proposes a hybrid CMV suppression method for the MTBBC, which adopts appropriate algorithms based on the voltage transfer ratio (VTR). When the VTR is lower than 0.5, a method is proposed to select the output vector group according to the input voltage intervals, where a vector group consists of three most remote voltage vectors, achieving a 71.1% reduction in the CMV peak and zero high-frequency CMV. When the VTR is higher than 0.5, the proposed method adopts the active zero state PWM method and the near state PWM method to reduce the CMV peak to 50%. Through the combination of three algorithms, the proposed method achieves superior CMV suppression and acceptable input-output performance across the entire VTR range. Experimental results verify the validity and effectiveness of the proposed method.