Unidirectional rectifier based on hybrid modular multilevel cascade converter — Double-star chopper-cells

In this paper a hybrid topology of Modular Multilevel Cascade Converter (MMCC) - Double-Star Chopper-Cells (DSCC) is proposed. This configuration is applied as a unidirectional controlled single-phase rectifier, wherein one of the converter legs is composed by diodes instead of the submodules (SMs) connections. In order to ensure the energy balance among the local SM capacitors, a voltage balancing control strategy is also presented. Besides, a grid current control strategy associated to a method that eliminates zero-crossing distortion caused by the diode leg is proposed, resulting in a power-factor correction (PFC) and a sinusoidal grid current. Experimental results are presented and allow validating the control strategies.