Comprehensive Analysis of SOGI-PLL Based Algorithms for Single-Phase System

The orthogonal signal generator (OSG) plays a crucial role in the synchronization of single-phase system under distorted grid condition. Power quality issues such as phase disturbances, voltage sag/swell, frequency oscillations, harmonics, and dc offset required fast and robust phase-locked loop (PLL) method to enhance stability of the grid-connected system. Among different PLL techniques, second-order generalized integrator (SOGI) based PLL has low computational burden and shows robust performance against hostile grid conditions. With requisite modification, it can show robustness towards dc offset and grid harmonic disturbances. This paper presents the mathematical modeling and performance analysis of SOGI-PLL, cascaded SOGI (CSOGI) PLL, second-order SOGI (SO-SOGI) PLL, modified SOGI (MSOGI) PLL, mixed second and third-order generalized integrator (MSTOGI) PLL. To improve the dynamic response of the PLLs, a new design approach is adopted to calculate the damping factor. Finally, the performance of different methods are validated by simulation and experimental results under voltage-sag, varying grid frequency, phase jump, and dc offset disturbances.