Advancements in DC offset rejection techniques: a comparative analysis of SOGI-PLL schemes

The rise of photovoltaic-based distributed power generation (PV-DPG) systems necessitates precise grid synchronization. To this extent, various PLL strategies have been introduced to facilitate smooth grid synchronization. In the case of three-phase systems, SRF-PLL has been widely implemented. For single phase system however, orthogonal signal generation-based PLL (OSG-PLL) is proposed but requires other supporting techniques for generating an imaginary phase. Transfer delay (TD) and second order generalized integrator (SOGI) have been proposed as promising aiding techniques for phase detection in single phase PLL. However, one challenging issue with the latter is that a slight DC offset can leads to unwanted frequency oscillations, thereby reducing the performance efficiency of the PV-DPG systems. This paper introduces a novel DC offset rejection scheme to eliminate these errors, enhancing the system performance. Analytical and simulation tests confirm the scheme's effectiveness, showcasing superior DC component rejection and harmonic attenuation compared to the other two existing offset rejection approaches.