Modeling and voltage balancing control for a hybrid stacked five-level converter

A capacitor voltage-balancing control strategy based on switching state redundancies is proposed for the hybrid stacked five-level converter. In order to obtain the balancing properties for flying capacitors, a hybrid model in state-space representation is established by considering the continuous and discrete variables. The proposed balancing strategy can control the flying capacitor voltages to track the reference value, and simultaneously ensure the desired voltage levels. The attractive characteristic of the proposed strategy is that no additional balancing circuit is required but simple measurements and logical judgments are needed. Moreover, the desired voltage levels can be generated by many different PWM schemes. A three-phase hybrid stacked five-level converter system is modeled in MATLAB/Simulink. Both steady-state and transient operation conditions are investigated to evaluate the effectiveness and robustness of the proposed control strategy.