There are two ways to solve the problem of midpoint potential fluctuation in the academic world: One is small vector adjustment based on SVPWM control; the second is zero-sequence voltage injection based on SPWM control. The midpoint potential balance control method used in this paper was an improved zero-sequence voltage injection method with correction control. Compared with the traditional zero-sequence voltage injection method, it took into account the advantages of traditional saddle-shaped modulated waves, and improved the over-modulation problem, and studied the practical zero-sequence voltage calculation method, which finally effectively suppresses the fluctuation of the midpoint potential, and the practical calculation method of checking and correcting zero sequence voltage is studied, the fluctuation of medium voltage point is successfully limited to 5 V, and the THD of grid side current is correspondingly reduced by 1%. Finally, the correctness and feasibility of the control method are verified by MATLAB/ Simulink software simulation and experiment.