Topology and modulation of asymmetrical hybrid multilevel inverter

A novel topology, referred to as asymmetrical hybrid multilevel inverter topology, was developed to solve the problems of enormous number of switching devices and low quality of output voltage of conventional multilevel inverter. It consists of asymmetrical multilevel inverter with clamped diodes and H-bridge multilevel inverter with the voltage source switchover between series state and parallel state. Under the same voltage levels, the number of switching devices reduced. The paper also presented a new modulation strategy, by which the most of switching devices can work at low frequency, the current backflow can be avoided with reduced switching loss and total harmonic distortion (THD) of output voltage, and then the amplitude modulation of continuous PWM can be realized. The validity of the proposed topology and control method was verified by simulation results.