A Novel SPWM Method with Voltage Balancing Capability for Multilevel Rectifier/Inverter Systems

This paper presents a novel SPWM control method with voltage balancing capability for the diodeclamped multilevel rectifier/inverter system. A complete analysis of the voltage balance theory based on a 5-level back-to-back converter is given. The voltage balancing effects of the triplen harmonic offset voltage added to all three phase voltages are discussed. The proposed control utilizes the offset voltage to control the average currents flowing into and out form the inner junction. The voltage balancing was achieved by selecting proper offset voltages for both sides. A 5-level experimental system has built up and used to prove the theory.