Voltage Balancing Control of Cascaded Single-Phase VIENNA Converter Based on One Cycle Control With Unbalanced Loads

A research study on a type of cascaded single-phase VIENNA converter (CSVC) is presented in this paper. And a type of DC voltage balancing control strategy for each cascaded module of the CSVC based on improved one-cycle control (I-OCC) is proposed, in which voltage balancing signals are added to the conventional OCC (C-OCC) control loop to cause a difference in the modulation signals of each of the cascaded modules, so that the DC voltages of all modules can be quickly balanced under unbalanced loads. At the same time, the average modulation wave maintains a constant value so that the CSVC achieves a unity power factor operation. The operating principle of the I-OCC strategy is discussed in detail, and the corresponding mathematical relationships are derived. In the proposed strategy, the ability to adjust the DC voltages is also analyzed. Finally, the simulation and experiment results are provided to verify the validity and feasibility of this I-OCC-based voltage balancing control strategy. The control strategy proposed by this paper is also applicable to all other cascaded unidirectional rectifiers.