A novel modulation strategy for three-phase four-leg matrix converters

A novel modulation strategy for three-phase four-leg matrix converters (3×4 MC) is proposed in this paper. A 3×4 MC consists of 12 bi-directional switches, one leg more than the conventional three-leg matrix converters (3×3 MC). The 4th leg provides a circulation loop for unbalanced components of load currents, as the neutral wire in three-phase four-wire power supplies. Existing control methods for 3×4 MC, such as space vector modulation (SVM), etc., are facing complexity of control and large amounts of calculation. Hence, they´re difficult to be implemented. In this paper, an average model of common mode output voltage of MC based on the method of two line voltage synthesis (TLVS) is built, which helps to predict the neutral-point voltage needed in each sampling period. The neutral-point voltage is obtained on the 4th leg by conducting its switches properly, thus realizing three-phase four-wire output. This method inherits the advantages of TLVS; moreover, it´s much simpler and easier for hardware implementation. At last, the vadility and feasibility of this method has been verified via simulation by MATLAB.