A single-phase cascaded H-bridge rectifier (CHBR) in the front end of the traction drive system of a transformer without power frequency is studied, and its mathematical model is constructed. On the basis of the voltage and current double closed-loop control strategy, the non phase-locked loop technology is introduced to improve the transient current control strategy. The grid-side current can quickly and accurately track the voltage phase frequency when the system is disturbed. Furthermore, the traditional additional balanced voltage control strategy has been improved, and the fuzzy control technology is added to solve the problems of unbalanced voltage and large voltage difference between all levels of capacitors on the DC side of CHBR when it is not ideal power grid or load is switched over a wide range. Finally, MATLAB/Simulink is used for simulation to verify the fast response and anti-interference ability of the proposed strategy during CHBR operation.