Two Signal Injection Methods for Sensorless Control of PMSM at Very Low Speeds

This paper introduces and compares two different sensorless vector control methods for permanent magnet synchronous motor (PMSM) drive at very low speeds and standstill. One of the methods is high-frequency (HF) signal injection method, which utilizes the magnetic saliency of PMSM. The other one is low-frequency (LF) signal injection method, which is based on the fundamental-wave model of PMSM. The former relies on the difference between d- and q-axis inductances, while the latter depends on the ripple of fundamental-wave back EMF. This paper compares the two methods on sensorless vector control of IPMSM by various simulations and finally gets some useful conclusions.