Universal PLL Strategy for Sensorless Speed and Position Estimation of PMSM

The implementation of the phase locked loop (PLL) structured observer in high frequency signal injection schemes requires tuning of the PI controller to lock on the rotor position. The PI controller is tuned depending on the signal to noise ratio (SNR) which is related to the amount of saliency/anisotropy presented in the machine, the amplitude and phase of the incoming modulated carrier signal. Thus, in case any of the mentioned factors changes then the PI has to be retuned again, otherwise it will loose track. In this paper a new PLL structure is suggested to avoid any disturbance that affects the demodulation and detection process. The new PLL scheme is totally independent of any machine parameters except the saliency/anisotropy, which is essential to obtain the rotor speed and position information.