Maximum Torque per Ampere (MTPA) Control of an IPM Machine Based on Signal Injection Considering Inductance Saturation

The aim of this study was to develop a new method to operate an interior permanent magnet synchronous machine (IPMSM) on the maximum torque per ampere (MTPA) condition. The characteristics of the MTPA condition were analyzed and the MTPA condition was derived based on the input electric power. The proposed method injects a small current signal used for tracking the MTPA operating point along with the fundamental current for torque generation. This method does not require any machine parameters or premade lookup table. The frequency of the injected signal is several hundred hertz, and the performance of the MTPA tracking is almost free from load torque disturbance. The feasibility of the proposed method was verified under various operating conditions with computer simulation and testing with an 11 kW IPMSM drive system.