Multiple-Loop Digital Control Method for a 400-Hz Inverter System Based on Phase Feedback

To keep phase balance and improve output voltage quality, a novel multiple-loop control system in 400-Hz inverter power supply based on unipolar sinusoidal pulse width modulation (SPWM) is proposed. The causes of phase imbalance in a three-phase combined inverter power system are analyzed, and a new multiple-loop control strategy based on phase control is presented to eliminate it. For reducing the total harmonic distortion (THD) of high-power inverter output, unipolar SPWM is added with this new control strategy. The designs of drive circuit and snubber circuit are discussed to eliminate dead time effects and voltage oscillation. The stability of the control system is analyzed and the power system and the control strategies are realized with digital signal processing. Contrastive simulation results indicate the advantages and the correctness of this novel controller for inverter. A three-phase combined inverter system based on a multiple-loop control strategy is constructed, and experimental results show that the inverter system can make a phase difference between each phase less than 2^°, and the THD of output voltage can be controlled within 2%.