Energy feedback device with composite unit cascade multi-level inverter circuit and control method of energy feedback device

The invention relates to an energy feedback device with a composite unit cascade multi-level inverter circuit and a control method of the energy feedback device. The energy feedback device consists of a power unit based on a three-phase control rectifying circuit and a power unit based on a three-phase PWM (pulse width modulation) rectifying circuit, wherein the two power units are in cascade connection. Direct-current voltage of an intermediate direct-voltage circuit of the power unit based on the three-phase control rectifying circuit is stabilized within a safety range by controlling a closed loop of the direct-current voltage of the intermediate direct-voltage circuit of the power unit based on the three-phase control rectifying circuit in a feedback manner, while load feedback energy mainly flows into the intermediate direct-voltage circuit in the power unit based on the three-phase PWM rectifying circuit and is fed into the power grid in a grid integration inverter mode by the three-phase PWM rectifying circuit. The energy feedback device is capable of realizing feedback of load energy to the power grid, so that energy-saving effect is achieved, output voltage is stabilized, and meanwhile, the topological structure of the power units and complexity of control links are simplified to some extent. Further, usage number of insulated gate bi-polar transistors is reduced, manufacturing cost is reduced as well, and the energy feedback device has high economic value.