An Improved High-Frequency Voltage Signal Injection-Based Sensorless Control of IPMSM Drives With Current Observer

An improved high-frequency (HF) pulsed sinusoidal voltage signal injection (HFPS-VSI) sensorless control strategy applied to interior permanent magnet synchronous motor (IPMSM) is proposed in this article. In the HF current signal demodulation process, this article proposes a demodulation approach that can demodulate a four times injection frequency component. Hence, a low-pass filter (LPF) with higher cutoff frequency can be selected to suppress the HF component. The proposed demodulation method can improve the bandwidth of the position estimation loop and increase the signal-to-noise ratio (SNR) of position angle errors fed to the rotor position observer. To enhance the current loop bandwidth, this article uses the current observer (CO) to extract the fundamental current. Theoretical analysis shows that the proposed fundamental current extraction method has no amplitude attenuation and time delay and is robust against motor parameter mismatches at the fundamental frequency. Therefore, it can eliminate the LPF used in the fundamental current extraction to improve the dynamic response of the current loop. Meanwhile, a design method of CO is proposed, which makes CO keep a constant and high bandwidth in the low-speed region, suited for low-speed sensorless operation. Finally, the effectiveness of the improved HFPS-VSI algorithm is verified by experimental tests.