Power balancing control of a multilevel converter using high-frequency multi-winding transformer

A novel multilevel converter is proposed where a high-frequency multi-winding transformer is applied to realize the isolation and energy balance instead of the conventional phase-shifting transformer. In the proposed topology, all of the DC buses are connected to the same high-frequency multi-winding transformer through separated H-bridge units. Load powers can be equalized among different windings by the energy delivery using transformer flux. Furthermore, the equivalent circuit is proposed consist of the high-frequency voltage source and high-frequency multi-winding transformer. The power relations between these H-bridge cells are analyzed. Based on these relations, power exchange law among different transformer windings is obtained with high-frequency square wave inputs and outputs. Moreover, a control strategy for power balancing by adjusting the phase of input voltage on each H-bridge unit is proposed. Experimental results are given to validate the proposed strategy.