An Improved Synchronous Frequency Extractors PLL with Low Computational Burden

The embedded magnetic encoder applies several linear Hall sensors in permanent magnet synchronous machine (PMSM) and estimates rotor angle from linear Hall signals. The angle estimation precision is decreased due to the inherent third harmonic component in linear Hall signals, which requires to be eliminated. The conventional synchronous frequency extractors (SFE) is a frequency adaptive selective filter, featuring good noise immunity. However, an extra frequency calculation module (FCM) is necessary to provides the fundamental frequency of input signals. In this paper, the computational cost of conventional SFE phase-locked loop (PLL) is released by replacing the FCM with the estimated frequency value from PLL. The start-up problem, introduced by above simplification, is addressed at the cost of two subtractions and one multiplication computational burden. The effectiveness of proposed SFE-PLL is proved through mathematical analysis and comprehensive experiments based on dSPACE.