DC voltage control strategy for a five-level converter

This paper describes a control method for a diode-clamped three-phase five-level PWM power converter considering the DC-link capacitor balancing problem. The proposed control circuit uses multiband hysteresis comparators (MHCs) to simplify the control of the main circuit. The DC-link capacitor balancing problem is solved by changing the shape of the MHC. The proposed method can: (1) overcome voltage imbalance in the DC capacitors; (2) achieve unity power factor; (3) generate nearly sinusoidal input currents; and (4) regenerate electric power back to the power system. Simulation and experimental results demonstrate the validity of the proposed method.