A new three-phase hybrid five-level inverter with reduced number of high-frequency switching devices

Multilevel converters find themselves more and more in low voltage and renewable energy applications due to their better harmonic spectra and less filtering requirements, in addition to conventional medium voltage industry drives and high voltage utility transmissions. This paper presents a new three-phase hybrid five-level inverter topology and the corresponding pulse-width modulation principle and switching pulse generation mechanism. The proposed five-level inverter has a modular structure, built by a regular flying-capacitor three-level inverter operated by PWM and a regular two-level inverter, which is switched only at line frequency. Compared to well-known multilevel topologies, the number of high frequency switching devices is reduced by one-third. Therefore, the proposed approach is able to reduce overall cost and switching loss while still producing an optimum output voltage spectrum and maintaining flying capacitor voltage balancing. Computer simulation results have verified the operation and feasibility of the proposed hybrid five-level inverter.