Study of Indirect One-cycle Control Strategy Based on Three-phase Z-source Grid-connected Inverter

In this paper, an indirect one-cycle control strategy based on three-phase Z-source network is proposed to solve the disadvantages of complex system and slow response in the conventional control mode. Combined with the relationship between input and output of Z-source impedance network, the mathematical model of three-phase Z-source grid-connected inverter is built based on state-average equations, and the control equation is deduced according to one-cycle control principle, which make inverter connect to power grid with unit power factor. Simulation results show that the three-phase Z-source grid-connected inverter based on one-cycle control can realize grid connecting with unit power factor in single power cycle (0.02s), the harmonic distortion rate of output current is less than 1%, and the output almost is not affected by input voltage fluctuation. Comparing with traditional Z-source grid-connected inverter, the indirect current control mode based on one-cycle control can achieve grid connecting with unit power factor rapidly in the absence of current sampling, which has such advantages as fast dynamic response, strong stability, and good robustness.