Duty-cycle-regulation based PWM control of five-level flying-capacitor inverter

Controlling voltage balancing of flying-capacitor multilevel inverter is very important for safe operation. Duty-cycle-regulation based PWM control is proposed, which can suppress capacitor voltage shifts caused by asymmetry of inverter installation such as delay mismatch of triggering pulses, and can also balance voltage distribution of capacitors when supply voltage increases abruptly in about two periods of carrier signal. Furthermore, it has good harmonic properties even during transients. In order to improve the control performance, current-predictive model is established to detect zero-crossing point of load current. The efficiency and validity of the method is demonstrated by simulation results.