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To improve the performance of the frequency lock loop (FLL) under the conditions of a distorted power grid and unexpected noise, this paper creatively introduces an active noise cancellation (ANC), which syncretizes two first-order low-pass filters (LPFs) to improve the frequency locking ability. Meanwhile, the improved SVSLMS algorithm (I-SVSLMS) for ANC is thoroughly discussed. What is more important is that the function and parameter selection of the two first-order LPFs are described, and 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. Compared with SOGI-FLL, COMB-FLL and AL-NF-FLL, the proposed 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. The results of simulation and experiment verify the effectiveness and reliability of the proposed method.INDEX TERMS Frequency-locked loop, grid synchronization, active noise cancellation, low pass filter I. INTRODUCTION