Accurate Phase Detection System Using Modified SGDFT-Based PLL for Three-Phase Grid-Interactive Power Converter During Interharmonic Conditions

Grid synchronization algorithm is used to track the fundamental phase angle and frequency of the grid voltages/ currents accurately, to generate the reference currents for control of grid-interactive power converters. Phase-locked loop (PLL) is vital in the grid synchronization technique. It is mandatory to track the phase angle and filter out the harmonics and interharmonics during distorted grid conditions. In this article, a modified sliding Goertzel discrete Fourier transform (SGDFT)-based PLL is proposed to extract the fundamental component during interharmonics conditions. The proposed PLL grants three degrees of freedom (DOFs), i.e., vigorous against several distorted grid conditions, namely, voltage sag, high-frequency harmonics, interharmonics, and dc offset. Furthermore, the proposed PLL precisely extracts the fundamental frequency and phase angle with the faster transient response and attains superior system stability. The detailed mathematical modeling of recommended PLL is analyzed with existing PLLs, such as harmonic, interharmonic, and dc offset PLL (HIHDO PLL), hybrid prefiltering stage PLL (HPFS PLL), and SGDFT-based PLL. The numerical simulations for the proposed PLL are carried out using MATLAB
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/Simulink environment and the performance of the recommended PLL is tested experimentally through the dSPACE 1104 DSP platform.