A digital phase locked loop based on frequency self-adaptive

Some independent micro grids occur serious frequency offset, which cause steady-state error in phase and frequency detection. This paper proposed a novel digital phase locked loop based on frequency self-adaptive filtering algorithm to improve the control performance of phase locked loop under frequency fluctuation and distortion grid conditions. Using two biquadratic butterworth band-pass filters real-time detect phase and frequency of the voltage of grid and extract fundamental component. The characteristics of Butterworth band-pass filter and the structure of digital phase locked loop was analyzed. The implementation of digital discrete domain was given. The simulation and experiment show that the proposed digital phase locked loop effective and feasible. The method can detect accurately the phase and frequency of the voltage of grid, and eliminate effectively detection error caused by frequency fluctuations and distortion of grid. It works in single-phase or three-phase system.