Abstract: The technical guidelines for grid-connected photovoltaic power generation require grid-connected inverters to achieve high power factor,and also set clear requirements for the total harmonic distortion（THD）of the grid-connected current. At present,the above goals are mainly achieved by modulating the grid-connected current of photovoltaic grid-connected inverters. Aiming at the operating characteristics of the photovoltaic quasi-Z source inverter,based on the working principle of the inverter’s two-state hysteresis current control,a three-state hysteresis controller and single-phase quasi-loop controller that can make the inverter pass through to achieve photovoltaic MPPT are proposed. The three-state hysteresis control system of the Z-source cascaded inverter is analyzed. The working principle of the three-state hysteresis controller is analyzed,and the three-unit quasi-Z-source cascaded inverter system is used to simulate the three-state hysteresis control and carrier wave. The control effect of the stacking method and the carrier phase shifting method. The simulation results show that the three-state hysteresis control modulation strategy exhibits better steady-state and dynamic response performance,and its grid-connected current harmonic distortion rate is smaller.