The Control Strategy of Buck-Type 3-1 MC Under Unbalanced Input Voltage

To optimize input current distortion, output voltage fluctuation, and other problems caused by a three-phase to single-phase matrix converter (3-1 MC) under unbalanced input voltage, the harmonic characteristic of the 3-1 MC input current is analyzed. A control strategy based on virtual dc current is proposed using input positive-sequence voltage as current reference vector, which avoids the dividing error of input sector by the positive-sequence voltage as reference vector. Through dynamic modulation ratio and stable output voltage, a pseudo-dc current is synthesized after the output phase current and decoupling phase current are modulated. A closed-loop control system is designed using the virtual dc current and deduced 3-1 MC mathematical model. Finally, the control strategy is validated by simulations and experiments and the control target of the input current harmonic and output voltage stability is achieved. The effectiveness and practicability of the control strategy are confirmed.