A Master-Slave-Structure Position Observer for Multiharmonics Suppression in Sensorless PMSM Drives

Due to the influence of inverter nonlinearity and nonideal spatial flux, it inevitably exists the back electromotive force (BEMF) harmonics in permanent magnet synchronous motor (PMSM) drives, affecting the accuracy of model-based position-sensorless control. Although different schemes have been studied to suppress the BEMF harmonics, it is still challenging to alleviate the contradiction between harmonics suppression effect and structure complexity. To address this problem, a master-slave-structure position observer is proposed for multi-harmonics suppression in this article. With the help of the master-slave structure, the fundamental frequency component of the BEMF is extracted as the output of the studied observer, realizing the separation from the harmonic components. The number of integrators can be reduced by half with complex-coefficient resonators instead of real-coefficient resonators. Thus, the design degree of freedom is fully exploited to realize the desired frequency-domain characteristics of band-pass and specific frequency band-stop. The studied method is verified by the experiments on a 2.2-kW PMSM platform.