A new modulation method for a five-level hybrid-clamped inverter with reduced flying capacitor size

In order to reduce the size of high-voltage flying capacitors in the five-level hybrid-clamped inverter, an improved modulation strategy based on phase-shifted PWM (PSPWM) is proposed in this paper. The four carrier waves are redistributed and the charge/discharge time of the high voltage capacitor can be largely reduced. The only disadvantage of this PWM scheme is that the harmonic characteristic will become worse. The harmonic characteristics of this method are studied and compared with traditional PSPWM method. Simulation results shows that the high-voltage flying capacitor value can be reduced by 90% while only the carrier-frequency harmonic components in the line voltage are increased. Experimental results are also presented to demonstrate the effectiveness of this method.