Enhanced DVR Control Using NF Assisted CSOGI-PLL under Diverse Grid Scenarios

Accurate and fast grid synchronization is critical for the control of Dynamic Voltage Restorers (DVRs) in 3phase power systems, especially in presence of diverse grid disturbances. The conventional Phase Lock Loop (PLL) and Second-Order Generalized Integrator (SOGI) based PLL often degrades in performance under voltage sags/swells, harmonic distortion or phase shifts etc. leading to poor DVR compensation. Therefore, for handling these disturbances, this paper designed Notch Filter (NF) assisted Cascaded SOGI (CSOGI-PLL) for three-phase DVR control and its performance has been comprehensively compared with multiple PLL techniques including PLL, SOGI-PLL, CSOGI-PLL, Enhanced PLL (EPLL) and SOGI-EPLL. The proposed technique employs a multi-loop structure in which an inner loop is used for extraction of multi-cycle fundamental and an outer loop for frequency and amplitude normalization; both, ensure robust phase and frequency tracking. Simulation are carried out in Matlab Simulink under voltage sag/swell, harmonic distortion, phase shift and frequency variation shows that the proposed PLL achieves lowest value of frequency overshoot (50.08 Hz) and having fastest settling time (20-25 ms) as compared to others. The multi-loop, normalized SOGI architecture provides enhanced harmonic rejection, fast transient response, and amplitude invariance making it highly appropriate for real-time three-phase DVR.