DSC-FLL Based Sensorless Control for Permanent Magnet Synchronous Motor

The (6k +/- 1)th harmonics exist in the extended electromotive force estimates due to the influence of the inverter nonlinearities and the flux spatial harmonics in the process of sensorless control of permanent magnet synchronous motor (PMSM), which give rise to the (6k)th harmonic in the rotor position estimate. A method of rotor position observation based on the time delay signal cancellation-frequency locked loop (DSC-FLL) is proposed to improve the sensorless control system of PMSM. The equivalent back EMF information is obtained by using the sliding mode observer, and the harmonic component in the specified back EMF observation value is filtered by using the delay signal elimination operator in the two-phase static coordinate system. The frequency locking loop is designed to track the rotor position information online, so as to improve the observation accuracy of the rotor position information. The model of sensorless control system of PMSM based on DSC-FLL is established and compared with the model of sensorless control system of PMSM based on arctangent function. The results show that after adopting the method of rotor position observation based on DSC-FLL, the high harmonic in back EMF is suppressed, the error of rotor position fluctuation observation reduced, and the error of rotation speed observation reduced. The observation accuracy of rotor position information is significantly improved.