A novel partial units energy feedback cascaded multilevel inverter with bypass control

This paper proposes a novel composite cascaded multilevel inverter, of which uncontrolled converters and pulse-width modulation (PWM) converters are connected in parallel. The proposed composite inverter could reduce the cost as compared with the pure PWM inverter, realize energy two-way flow and simplify the structure design of the phase shifting transformer. This paper adopts bypass control strategy to make the renewable energy wholly fed back through the PWM power units. To verify the proposed technique, this paper designs a three-phase cascaded multilevel medium-voltage inverter composed by five cascaded units, of which three are energy feedback units. Investigations using MATLAB/Simulink based simulations and an experimental prototype confirm the practicability and validity of the proposed technique.