MTPA Based Direct Torque Control for Energy-Efficient Operation of Induction Motors in Electric Vehicles

This paper presents a demonstration of the maximum torque per ampere (MTPA) based direct torque control (DTC) scheme for improving the energy efficiency as well as dynamic response of induction motor drives used in electric vehicles. The flux reference for MTPA condition was first formulated in the synchronous frame of reference and then it was converted into stationary frame of reference for implementing the DTC scheme. The MTPA controller was modified to incorporate the core losses and the DTC scheme was tested for varying torque reference. The results show that the MTPA based DTC scheme draws lesser current from the inverter than the traditional DTC scheme especially at light loads. This can lead to energy savings in electric vehicles in which the requirement of torque varies widely. An electric vehicle (EV) was modelled in Matlab-Simulink software and simulated to compare the performance of the MTPA based DTC scheme and the traditional DTC schemes for FTP75 drive cycle. The simulation results show that the MTPA based DTC controlled induction motor drives provides significant energy savings in electric vehicles for the specified drive cycle. The MTPA based DTC scheme was also experimentally verified on a laboratory prototype.