Six-leg single-phase multilevel rectifier-inverter: PWM strategies and control

This paper discuss a rectifier-inverter composed of two three-leg converters with unequal DC-links connected in series. This increases the number of voltage levels and contributes to reduce harmonic distortion and losses. Several PWM strategies are discussed (Space-Vector, Level-Shifted and Hybrid Level-Shifted PWM). The balance of separated DC sources is addressed in this paper. In order to achieve this, an adapted version of Level-Shifted PWM is developed. A feedforward controller is used to control the average value of the DC voltages. Simulation results compare losses and harmonic distortion of Three-Leg and Six-Leg topologies. Experimental results are provided to validate the feasibility of the system.