A Novel Suppression Method for Position Estimation Error in Sensorless Control of Electrolytic Capacitor-Less PMSM Drives

— The permanent magnet synchronous motor (PMSM) drives using small-capacity film capacitors has the advantages of high-power density, low cost, and long service life. However, large fluctuations appear in the dc-link voltage and system power according to the small capacitance of the dc-link capacitor. This will result in many additional harmonic components in the back electromotive force (BEMF) and flux linkage, which could deteriorate the performance of the sensorless control and cause the large position estimation error. Hence, a novel flux linkage observer (FLO) using generalized integral master-slave filter (GIMSF) is proposed to suppress the harmonics. GIMSF is composed of multiple generalized integral structures with different center frequencies, and it has not only the bandpass characteristic, but also the band-stop characteristic. After extracting the flux linkage through GIMSF, the rotor position and speed could be estimated through the phase-locked loop (PLL). In addition, the accuracy of the PLL is also affected by the harmonics caused by the inductance asymmetry and current sampling error. Hence, an improved PLL is proposed to further eliminate the impact of harmonics on the estimated position. Finally, the effectiveness of the proposed method is verified by experimental results.