Design of Single-Phase Digital Phase Locked Loop Based on MVF-QSG

Abstract

QSG (quadrature signal generator) is the critical part of single-phase PLL. In order to effectively reduce the influence of DC components and harmonics on orthogonal signals, a QSG based on multivariable filter (MVF) is proposed, and it’s proved to have good frequency adaptability. In this paper, the author first analyzes the transfer function of MVF, theoretically analyzes the mechanism of its attenuation of DC and harmonics, analyzes the influence of parameter Kf on MVF-QSG, uses MATLAB to simulate the working performance of MVF-QSG on DC components and harmonics under steady state and dynamic conditions and the working performance under the conditions of abrupt voltage frequency variation, and finally establishes a 3kW grid-connected inverter platform, verifies MVF-PLL's phase-locking effect under the conditions of power grid amplitude step and distortion by experiments, and proves the feasibility of the method.