The main circuit of the traditional single-phase cascade H-bridge rectifier is improved, the power decoupling arm is added, the mathematical model is established, and the voltage balance and ripple suppression strategies are studied. Firstly, the whole loop is controlled by double closed-loop, and the extraction scheme of fundamental signal is optimized by the second-order generalized integration method. Secondly, the power balance relationship of the system is derived, the primary relationship model of the grid-side current and the capacitance voltage squared is established, and the variable proportion link is introduced to effectively improve the robustness of the system to resist parameter changes. Then, the independent Buck-type active power decoupling control strategy is adopted, and the duty cycle of the decoupled bridge arm switch tube is distributed in real time by calculation, and an adaptive frequency selector is designed to separate the secondary ripple signal to realize the suppression of the secondary ripple voltage ripple of the DC bus. Finally, the experimental verification based on Matlab/Simulink software shows that the proposed method can effectively solve the problems of voltage balance and secondary ripple power suppression.