Unbalanced thrust control of multiple induction motors for traction system

Multiple induction motors (IM) fed by a single inverter are generally applied in traction system, such as rail transportation. The characteristics of the thrust difference are theoretically analyzed firstly. A novel control strategy based on weighted voltage vector is proposed to relieve the thrust difference in each wheel with induction motor. The essence of weighted voltage vector is to select suitable slip for the rotor flux oriented vector control. The weights of each voltage vector are calculated by the thrust regulator to obtain new voltage vectors. Results show that unbalanced thrust can be reduced more than 50% comparing proposed method to conventional method. This strategy can be applied in practical traction system driven by multiple induction motors.