Active compensation for supply voltage unbalance on two-stage direct power converter

It is known that the output voltage capability of Matrix Converters (MC), which has no energy storage, is seriously affected when the supply voltage is unbalanced. Passive compensation methods improve the waveform quality of the output, but provide reduced output voltage depending on the level of unbalance. This paper proposes an active compensation technique for unbalanced supply voltages in the two-stage Direct Power Converter (DPC). The technique is based on the utilisation of the clamp capacitor, which is normally needed to protect a MC, to extend the operating range of a two-stage DPC during unbalanced supply, preserving its theoretical output voltage capability. A comprehensive simulation study with analytical explanations justifies the proposed method. Experimental results using a laboratory prototype confirms the viability of the proposed active compensation technique.