AC-DC Matrix Converter with Positive and Negative Output Capacity in Unbalanced Grid

The study of AC-DC matrix converter under unbalanced power grid is mostly focused on the suppression of the two harmonic of output voltage. In this paper, the voltage type AC-DC matrix converter under unbalanced power network is studied, focusing on the control of the three-phase current in the grid side and the predictive unbalance control strategy with negative sequence voltage compensation is proposed. The strategy can suppress the current harmonics of the grid side, realize the unit power factor and the effect of grid side current sine and high balance under unbalanced power grid, and eliminate the grid side current distortion, in order to reduce the pollution to the power grid. In this strategy, new voltage feedforward quantity is get by the negative sequence voltage compensation and the number of regulators in the current loop in the dq frame is reduced, so that the controller parameter design is greatly simplified. And a de-re-couple SVM modulation strategy with voltage command signal basing on the positive and negative switching is proposed, so that it can meet the requirements of the AC-DC matrix converter with positive and negative output capacity under unbalanced network.