A Sensorless Control Method With Identification of Stator Inductance for IPMSM at Low-Speed Under Low Switching Frequency

High-frequency (HF) voltage injection methods are usually used in sensorless control for interior permanent magnet synchronous motor (IPMSM) at low-speed. The stator resistance is ignored when the frequency of HF voltage is high enough. However, in high power application, the frequency of injected voltage becomes low and limited to low switching frequency, which leads to rotor position estimation error due to ignoring stator resistance. Moreover, the phase delays caused by the filter and large system delay under low switching frequency bring estimation error, which changes with speed and cannot be directly compensated. Therefore, this article proposes a sensorless control by injecting HF voltage at one-third of the switching frequency. To reduce the influence of stator resistance on the estimated result, the HF current generated by the fifth harmonic of injected HF voltage is adopted to estimate rotor position, which increases the equivalent frequency of the HF signal. To eliminate the estimation error caused by filter and system delay, an adaptive compensation strategy for total disturbance is applied. Besides, the voltage and generated current at injection frequency are adopted to identify the stator inductance by recursive least squares (RLSs), which improves the performance of torque control. The proposed methods are verified by simulation and experimental.