Study On Field-weakening Control Of Induction Motor In High-speed Train

ABSTRACT:With the rapid growth of high speed train, wide speed control system is becoming more and more important. Variable voltage and variable frequency system based on vector control is applied widely in high speed train. In this system, it must adjust the stator voltage and frequency at the same time to adjust motor speed. When frequency is up to the base frequency, the amplitude of voltage vector is restricted constant. Field-weakening control can make the motor running over the rated speed and meet the wide speed range of high speed train.In the field weakening region, the torque capacity decreases with the increasing frequency, torque output capacity depends largely on the field-weakening control strategy. The conventional vector control is not applicable as it requires controllability of both the amplitude and the phase of the voltage vector for all time, so the torque capacity can't play fully, the actual output torque can not follow the given torque. This paper uses effective optimization strategy to increase torque output capacity through studying the motor running state in the field weakening region.This paper analyses the operation conditions under the limits of voltage and current based on the induction motor mathematical model and presents flux compensation and phase compensation control method through analyzing the operating characteristics of induction motor in different region. The flux compensation control coordinates d, q axis current so as to produce the maximum torque by changing the flux curve form while the phase compensation control changes the phase of stator current.This paper sets up the vector control model based on the high speed train of CRH2A under the Matlab/Simulink environment. The simulation uses the traction motor parameters and traction characteristic curves of CRH2A to verify the two strategies. The flux compensation strategy is also realized based on a 7.5kW experimental motor platform. Experiment and simulation results show that the proposed methods are effective for increasing motor output torque, and the results verify the validity of the theoretical analysis.