Coordination Control of Modulation Index and Phase Shift Angle for Current Stress Reduction in Isolated AC-DC Matrix Converter

Due to the potential for high power density and high efficiency, the isolated ac-dc matrix converter is an attractive alternative for voltage source converters in applications requiring isolation and bidirectional power flow. However, existing control schemes fail to coordinate the modulation index and phase shift angle, and instead focus on optimizing one of the two variables. This can cause high current stress on the high frequency transformer, leading to low efficiency under a light load. To optimize the operation of the isolated ac-dc matrix converter, the coordination control of the modulation index and phase shift angle is proposed in this article to suppress the peak current of the transformer. First, a mathematical model based on Fourier transform is established to calculate the current stress. Then, the combination of the modulation index and the phase shift angle is obtained to minimize the current stress and improve the converter efficiency. Experimental results on an isolated ac-dc matrix converter are provided to verify the effectiveness of the proposed method.