Self-precharge of floating capacitors in a five-level ANPC inverter

Five-level active neutral-point-clamped (ANPC) converter is a newly emerging topology which can overcome the drawbacks of traditional neutral-point-clamped and flying-capacitor multilevel converters. During the start-up of the converter, it must be ensured that the switches and capacitors cannot be overvoltage and overcurrent due to the uncharged floating capacitors. In this paper, a floating capacitor self-precharge method is proposed which, by transferring the circuit into a booster, charges the floating capacitors to the reference voltage with a very small average load current. Simulation and experimental results are presented to verify the validity of this method.