Self-adjusting strategy based on rotating injection for sensorless control of high-power PMSM drives

As a sensorless control method suitable for permanent magnet synchronous motor (PMSM) at low-speed, rotating high-frequency injection method will face some special problems in high power applications. On the one hand, the low switching frequency limits the injected signal frequency, which is very close to the fundamental frequency. On the other hand, under heavy load conditions, the fundamental current amplitude is several hundred times of the negative sequence current. This will result in difficulty in signal extraction. In this paper, current spectrum is analyzed quantitatively based on the parameters of PMSM drive for rail vehicles, which illustrates the limitations of conventional bandpass filters. A method based on self-adjusting filter is proposed. The negative sequence current is successfully extracted, and the precise rotor position is obtained under the condition of variable speed and variable load. Based on a full-scale test platform the effectiveness of the proposed method is proved.