Adaptive Phase Synthesizer With In-Loop Variable Gain Control for Reliable Grid Integration

Modern electrical distribution networks face challenges from dc offsets and harmonics within the grid voltage, often caused by nonlinear loads or power electronics devices. This article proposes a phase-locked loop (PLL) as an adaptive phase synthesizer with in-loop variable gain control (VGC) to achieve reliable grid integration. The design of this PLL builds upon a type-3 in-loop filter-based second-order generalized integrator (ISOGI), known for effective dc offset and harmonics filtering. To optimize transient performance, the ISOGI-VGC structure is introduced. The VGC controller provides dynamic bandwidth adjustment, enhancing both transient and steady-state response. Comparative simulations demonstrate the superiority of the proposed PLL design under various grid disturbances. Further validation is provided through a hardware prototype tested on a dSPACE real-time platform. The results confirm that the ISOGI-VGC-based type-3 PLL delivers improved performance and reliable grid integration.