Taking the cascaded H-bridge rectifier (CHBR) of power electronic transformer (PET) in the traction drive system of the new electric locomotive without power frequency transformer as the research object, the CHBR mathematical model of power electronic transformer is established. Based on the theory of instantaneous power, a new type of power electronic transformer CHBR DC capacitor voltage balance control strategy is pro- posed. At the same time, the unit power factor of the system under non-ideal traction network voltage is realized. Finally, the computer simulation software is simulated by Matlab / Simulink, and the simulation results show the effectiveness and superiority of the proposed control strategy.