A Luenberger observer-based phase locked loop for single-phase systems under harmonic disturbances

摘要

Harmonics in single-phase systems challenge the performance of quadrature signal generator-based phase-locked loops (QSG-PLLs). This paper proposes a Luenberger observer-based PLL (LO-PLL) to address the issue. The proposed method enhances the harmonic suppression capability when estimating the fundamental grid voltage, thus leading to improved system harmonic rejection robustness. In detail, the improvement is enabled by the integrated grid voltage, which is mathematically established in this paper. Subsequently, the observer is adopted to generate the fundamental grid voltage and its quadrature signal. The resultant two signals for synchronization are highly robust against arbitrary-order harmonic disturbances, especially for interharmonics and noises. More importantly, as the poles of the observer can be designed flexibly, fast dynamics and strong harmonic robustness can be ensure for the entire PLL system. Experiments verify the performance of the proposed LO-PLL in terms of high harmonic immunity and fast dynamics.