Low-Order Measurement Offset Rejection Methods in Single-Phase SOGI-PLL

Conventional second-order generalized integrator (SOGI) phase-locked loop, designed for dc offset (DCO)-free measurements, experiences significant accuracy degradation in the presence of DCO. To tackle this issue, the literature offers various solutions, including low- and high-order methods. This letter focuses on low-order methods due to their computational and implementation simplicity. It has been modeled, tuned, and systematically analyzed for the first time using a constructive approach and three key low-order DCO rejection methods: extended state SOGI (ESOGI), third-order generalized integrator (TOGI), and low-pass filter-based SOGI (LSOGI). Results indicate that LSOGI and TOGI share similar time- and frequency-domain characteristics, while ESOGI prioritizes fast dynamic response over steady-state accuracy. Therefore, careful consideration is necessary when choosing DCO rejection methods based on specific application requirements. The results presented here offer explicit guidance in this context.