An Improved Modulation Scheme of Isolated Matrix Converter for Common-Mode Voltage Reduction and DC-Bias Current Mitigation

In this article, an optimized space vector modulation method is proposed for the isolated three-phase matrix-type ac/dc converter, where the four-quadrant operation ability of the bidirectional power switch can be fully used. The primary-side transformer current can be eliminated naturally during zero current vectors without extra switching actions. Therefore, the conduction loss of matrix converter (MC) is reduced and the efficiency can be increased. Moreover, the proposed method can avoid the shoot-through operation in MC, and the common-mode voltage can be mitigated effectively. As the zero current vector is kept with the proposed modulation strategy, the current harmonics will not be increased. Thirdly, both the dc-link inductor current and dc-bias current of high-frequency transformer (HFT) are measured through the secondary-side current of HFT. Therefore, the dc-bias current and the saturation of HFT are avoided by closed-loop control with the proposed modulation strategy. The experiments have been carried on a 1-kW laboratory prototype to verify the validity of the proposed modulation scheme.