Control characteristics of an induction motor speed sensorless control system for the railway vehicle traction

In this paper, we discuss theoretically the characteristics of an induction traction motor speed sensorless control system applied to the DC electrified railway vehicle traction. A state equation is derived from linearized equation models of the speed sensorless control system including the DC input filter circuit, the inverter and the induction motor. By means of bode diagrams, we discuss torque current control characteristics, the characteristics against the rotor frequency disturbance and against the sudden change of the line voltage, comparing the control system with the speed sensor. Through the study, we conclude that the suggested speed control system has high enough performance to be applied to railway vehicle traction.