A novel technique of low frequency input current ripple reduction in two-stage DC-AC inverter

The input current of the two-stage DC-AC inverter contains low frequency ripple whose frequency is twice that of the inverter´s output voltage. The proportion of the low frequency current ripple´s amplitude to the average current´s can achieve as high as more than 30%. The stability of dc power system and life span of the input voltage source such as battery or fuel cell could be influenced seriously. The reason of low frequency input current ripple production is analyzed, and the new control strategy of the first stage DC/DC converter is proposed on this paper. Compared with the traditional control strategy, the resonant controller is introduced. The proposed new control strategy is effective in reducing the current ripple in the output filter inductor of the DC/DC converter. Moreover, the input current ripple of the two-stage DC-AC inverter can be decreased. The design of the resonant controller and the system transfer function are given in the paper. The design principles of system stability are also discussed. At last, the effectiveness of proposed new control strategy to reduce the input current ripple that exists in the two-stage DC-AC inverter is verified by simulation and experimental results.