Frequency-Locked Loop Based on Active Noise Cancellation Syncretized Two First-Order Low Pass Filters

Abstract

To improve the performance of the frequency lock loop (FLL) under the conditions of a distorted power grid and unexpected noise, a new type of frequency locked loop (Al-FLL) is proposed, in which the AL-FLL prefilter is formed by fusing two first-order low-pass filters (LPFs) with an improved active noise cancellation (ANC) method. Firstly, the improved S function variable step size least mean square algorithm (I-SVSLMS) is discussed and its performance is verified under different signal to noise ratio conditions. Secondly, the function and parameter selection method of LPFs are described. Finally, the stability of the whole system is analyzed. In addition, the denoising work is completed in the synchronous reference frame and the output frequency of the FLL is fed back to the Park transform as the rotation frequency, which further improves the dynamic response and steady state performance of the FLL. The results of simulation and experiment verify the effectiveness and reliability of the proposed method. Compared with the FLL based on second-order generalized integrator (SOGI-FLL), the Comb Filter based on FLL (COMB-FLL), and the AL-FLL without frequency feedback (AL-NF-FLL), the AL-FLL has the advantages of small computation, fast response speed, and small steady-state errors, etc., and it is fully competent to work under the conditions of power grid distortion and unexpected noise.

Keywords

• Frequency-locked loop
• grid synchronization
• active noise cancellation
• low pass filter