Maximum Torque per Ampere Control for IPMSM Traction System Based on Current Angle Signal Injection Method

Rail transportation interior permanent magnet synchronous motor traction control system (IPMSM TCS) requires high torque output capability. Traditional algorithms used to find the maximum torque per ampere (MTPA) operating point in TCS have strong dependence on motor parameters. Because the algorithm is less robust to motor parameters, there will be deviation between the MTPA operating point and the actual value when the parameters change, so that it is difficult to guarantee the torque output capability of the traction system under different working conditions. This paper introduces a current angle signal injection control method (CASIM) to solve this problem. The proposed method tracks the MTPA operating point and generates d-axis current command according injecting an angle signal to current and making the partial derivative of torque to current angle equal to zero. At the same time, less motor parameters are needed to calculate the torque in this method. Consequently, in the process of looking for MTPA operating point, the accuracy is less affected by the variation of motor parameters. And also it does not inject any real signal to IPMSM, so that it does not increase copper and iron losses. Moreover, it is robust to speed mutation and torque disturbances. The effectiveness of CASIM proposed in this paper is proved by simulation and experiment results on an IPMSM TCS platform.