Improved Capacitor Voltages Balancing Control for Five-Level Hybrid Flying-Capacitor Inverter

In this paper, an improved capacitor voltages balancing control for five-level hybrid flying-capacitor (5L-HFC) inverters is proposed. The 5L-HFC inverter has advantages of having lower voltage stresses of active switches comparing to the five-level active neutral-point-clamped (5L-ANPC) inverter. The 5L-HFC inverter requires either auxiliary balancing circuits or a control algorithm utilizing phase-shifted PWM (PSPWM) to achieve capacitor voltage balancing. However, the former method requires the additional devices and the latter incurs worse THD of line-to-line voltage. In this paper, thus, a novel capacitor voltage balancing control method with better THD and without auxiliary circuits for the 5L-HFC inverter by controlling the duty ratios and selecting the redundant states based on COPWM. The proposed method has been verified through simulation result at various conditions.