A Multiharmonics Suppression Backstepping Extended State Observer for the PMSM Electrolytic Capacitorless Drives Sensorless Control

The electrolytic capacitorless driver has a longer service life and higher reliability than traditional permanent magnet synchronous motor (PMSM) drivers. However, the ac component in the dc-link voltage will generate corresponding harmonics in the back electromotive force (BEMF), which will reduce the control accuracy of sensorless. The traditional extended state observer exhibits low-pass filtering characteristics, making it difficult to accurately estimate the BEMF that varies sinusoidally and effectively suppress the BEMF harmonics. Therefore, a multiharmonics suppression backstepping extended state observer (M-BESO) is proposed in this article. The BESO is designed in reverse according to the amplitude frequency characteristics of the bandpass filter, so that the center frequency changes with the motor frequency. Then, the complex coefficient module is introduced into the structure of BESO to eliminate the harmonics in the BEMF caused by the fluctuation component of the dc-link voltage. To mitigate the position estimation error when the motor speed changes rapidly, an improved phase locked loop based on third-order extended state observer is designed. Finally, the proposed method is verified on a self-built experimental platform based on the PMSM electrolytic capacitorless drives.