Direct Torque Control of Traction Motor Fed by Four-switch Inverter with Virtual Voltage Vector

It is necessary to ensure the traction driving system can survive from fault condition when the open-circuit or short-circuit fault of power electronic device occurs. The direct torque control system of traction motor based on fault-tolerant inverter is proposed in this paper. The basic principle of three-phase-four-switch traction inverter is introduced. Moreover, the direct torque control scheme based on virtual voltage vector for traction motor is designed. Meanwhile, an improved observer of stator flux with saturation limiter is employed to restrain the integral drift. Then an approximately circular flux linkage trajectory controller is designed, and the starting excitation scheme is given. Finally, MATLAB/Simulink simulation is carried out to verify the validity and effectiveness of the proposed control strategy.