Frequency Adaptive Grid Synchronization Detection Algorithm Based on SOGI

In response to the complex working conditions of the power grid caused by the high proportion of new energy access, which leads to insufficient output accuracy of the second-order generalized integrator (SOGI) phase-locked loop, this article proposes an improved frequency adaptive phase-locked loop structure for SOGI. Firstly, an amplitude compensation branch is introduced to compensate for the SOGI tracking fundamental frequency signal, ensuring the accuracy of the SOGI output orthogonal signal under frequency fluctuation conditions. Secondly, by cascading two adaptive SOGI modules, the suppression capability of low-order harmonics and Direct Current (DC) components has been improved. Finally, the positive and negative sequence separation method of orthogonal signals is introduced to eliminate the influence of unbalanced components on the phase-locked loop. The comparative experiment with the classic SOGI-PLL method shows that the proposed phase-locked loop structure effectively improves the accuracy of power grid synchronization detection under complex working conditions such as harmonic components, unbalanced components, and frequency fluctuations. It can complete frequency detection within 1.5 power frequency cycles, and the detected fundamental frequency positive sequence voltage has a higher sinuosity and harmonic distortion rate within 0.5%.