DC-link Voltage Balance Strategy for Three-Phase Cascaded H-bridge Rectifier Based on Logic Combination Modulation

Cascaded H-bridge Rectifier (CHBR), the key component of Power electronic transformer, is faced with the challenge of DC-link voltage balance. This paper proposes a DC-link voltage balance strategy realizing it by Logic Combination Modulation (LCM). The mathematic model of the topology, the control strategy of three-phase CHBR, and basic modulation of the cascaded converter have been designed. The theoretical analysis, simulation, and experiment have been done to verify the stability, effectiveness of the proposed strategy. Also, the limitation of the proposed strategy is calculated and proved. The LCM could balance the DC-link voltage while one module is no-load under 0.83 modulation depth.