Rotor Temperature Monitoring and Torque Correction for IPMSM of New Energy Vehicle

As the electric vehicle market grows rapidly, thermal analysis related to the performance of electric drive motors has gained increasing interest. However, it is hard to obtain rotor temperature for torque correction during operation which leads to unexpected inaccurate control of motors. Rotor temperature monitoring and torque correction for IPMSM (Interior Permanent Magnet Synchronous motor) of new Energy vehicles are discussed in this paper. Considering the practical application, a low-order lumped parameter thermal network (LPTN) composed of three nodes is built for calculating the rotor temperature under different operating conditions on a 160kw IPMSM of a three-in-one electric drive. To identify the parameters of LPTN, the measurements were done on a test bench with a prototype of the three-in-one electric drive. K-type thermocouples were used to directly measure the temperature of each node. The data transmission of rotor temperature was realized by a wireless transmitter and receiver. Then, by measuring the back EMF with no-load at different rotor temperatures, the curve of flux linkage and rotor temperature was achieved. Finally, the Field oriented Control strategy of IPMSM was optimized with torque correction based on the rotor temperature model. A comparison test was performed in specified operating conditions of IPMSM between the base model and the optimized model of torque control. The test data indicates that under a speed of 16000rpm and torque request of 50Nm, the maximum measured torque deviation decreases from -8.28% under the base model to -1.66% under the Optimized model. The torque correction based on the rotor temperature estimate can effectively improve the torque control accuracy in the three-in-one electric drive.