A Simple Yet Robust Mechanism for the Improvement of Phase-Locked-Loop System and its Verification with Grid Side Converter Control

Abstract

The increasing number of nonlinear loads and the integration of renewable energy sources into the grid make the conventional SRF-PLL less accurate for estimating the phase and frequency of the grid voltage. A variety of enhanced filtering-based PLLs have been reported in the literature to solve this issue. However, these techniques are computationally more complex. For this reason, a method has been proposed to improve the performance of low pass filter (LPF)-based SRF-PLL, which is easy to implement and is computationally less expensive. In this paper, two in-loop second-order notch filters have been used with an LPF to nullify the effect of dominant lower order harmonics. The dynamic performance of the proposed technique is improved by implementing a PID type loop filter. The proposed scheme is compared with the other methods, like MRF-PLL, conventional and LPF-based SRF-PLL. The response of the proposed PLL is found to be encouraging under different grid disturbances. The efficacy of the proposed PLL has been verified by implementing the current controller to control the active and reactive grid current for the grid side converter in the hardware setup.