A recursive DFT based technique for accurate estimation of grid voltage frequency

This paper proposes an estimation technique of the single-phase grid voltage fundamental frequency under distorted conditions. The proposed frequency estimation technique relies on a band-pass filter and an algorithm based on three consecutive samples. The band-pass filter relying on the recursive discrete Fourier transform (DFT) and inverse recursive DFT is used to extract the instantaneous grid voltage fundamental component. The algorithm based on three consecutive samples is then used to estimate the grid voltage fundamental frequency. The estimated frequency is used to synchronize the window size of the band-pass filter with the period of the grid voltage waveform. The proposed frequency estimation technique is relatively simple, computationally efficient and can also estimate the fundamental frequency accurately from a grid voltage waveform distorted by DC offset and harmonics. Simulation results are presented to verify the performance of the proposed technique.