Spatial Equivalent Impedance Model Based Initial Position Detection for PMSM with High-Frequency Injection

Accurate initial position detection is important for enhancing the start-up performance of permanent magnet synchronous motors (PMSMs). However, the conventional high-frequency (HF) injection methods make it difficult to estimate the accurate initial position in PMSMs with low saliency ratios and significant cogging harmonics. To address these issues, this paper proposes a spatial equivalent impedance model (SEIM) based initial position detection method. Firstly, a quasi-sinusoidal functional model containing the spatial equivalent impedance information is established, where the effect of cogging harmonics on initial position detection can be reduced. Moreover, the overall spatial equivalent impedance information is considered in the proposed method, which improves the estimation accuracy on low-saliency PMSMs. To suppress the fluctuation error of estimation results, a variable forgetting factor sliding discrete Fourier transform (VFF-SDFT) algorithm is presented. Furthermore, to enhance the universality of the proposed method, an adaptive HF amplitude selection method based on split-step HF injection (SSHI) is given. In the same process, the magnetic polarity detection is achieved simultaneously by HF current peak-value accumulation, where the process of dual-pulse injection can be eliminated. Finally, the proposed method is verified on a 2.2-kW IPMSM and a 7.5-kW SPMSM.