Design and Application of Complex Vector Current Controller for IM Based on Ripple-Free Minimum Beat System

In the AC drive system of urban rail transit, in order to reduce the loss of switching devices and improve the output power of the converter, the switching frequency of the traction converter is usually low, resulting in a considerable digital control delay, which intensifies the coupling between the motor excitation current and the torque current. To solve the above problems, the paper comprehensively analyzes the mathematical models of the traction induction motor (IM) in the S domain and Z domain, and the coupling factors caused by the digital control delay. Combining with the design method of ripple-free minimum beat system, an optimized complex vector current controller for the traction IM is proposed. In the discrete time domain, the current controller not only ensures an excellent dynamic response performance; Moreover, it can realize effective decoupling between the excitation current and torque current. Through Matlab/Simulink simulation and testing with CRH6F-A intercity Electric Multiple Unit (EMU) IM traction converter, the effectiveness and feasibility of the optimized complex vector current controller are proved.