Power Quality Improvement in PV System Tied to Weak Grid

Abstract

An integrator-based positive sequence estimator control is presented in this article for the enhancement of power quality of a grid interfaced double stage solar PV system. This control extracts positive sequence components from the grid voltages (distorted and unbalanced) for the computation of unit templates and grid reference currents even during grid anomalous situation of distortion, unbalance, sag/swell, dc offset, etc. In order to achieve a rapid transient response of the system, a feedforward term for the photovoltaic array is also applied. The dc-link voltage is also adjusted adaptively for the reduction of the voltage source converter losses during the conditions of the weak grid. The system with an integrator-based positive sequence estimator control is simulated in the environment of MATLAB and experiments are performed on a prototype built in the laboratory. Simulation and experimental results validate the satisfactory system performance at different odd states such as intermittent solar irradiations, dc offset, voltage distortions, unbalance, voltage sag, and swell. During the grid disturbance and other intermittent conditions, grid currents total harmonics distortion is found as per the IEEE standard-519.