Enhancing the Current Quality of Four-leg Direct Matrix Converter Under Unbalanced Loads

With the lack of dc-link capacitor in the direct matrix converter, the disturbance in the output will be immediately reflected in the input. The four-leg direct matrix converter can fed an unbalanced three-phase load. Feeding unbalanced loads leads to input current distortion. In this paper, a simple method known as model predictive control for regulating the current reference of four-leg direct matrix under unbalanced load is presented. It is implemented by selecting the optional switching state in the subsequent sampling period of the converter by evaluating the cost function. This proposed method can narrowly achieve the desired load current. Moreover, it gains the sinusoidal source current with degrading the load current slightly by adding the source current error to the cost function and selecting the appropriate weighting factor. The simulation results verify the correctness and the feasibility of the method.