IIR Digital Filter based Discrete SOGI Controller and Discrete DSOGI PLL for Grid Integrated Solar Photovoltaic System

Abstract

In this paper, a discrete second-order generalized integrator (SOGI) control algorithm is implemented in a two-stage grid-tied solar photovoltaic (PV) system. The control strategy is entirely designed in the z-domain. This paper presents an easy and accurate way to execute the discrete SOGI control algorithm using IIR digital filter. The implemented algorithm extricates the fundamental component from the currents of the non-linear load. This control technique offers the benefit in terms of harmonic elimination, correction in power factor, and load balancing functionality. In addition, the control algorithm provides excellent performance in steady-state and dynamic conditions owing to the inclusion of solar photovoltaic power feed-forward term. The reference current is extracted using the implemented discrete SOGI control algorithm for controlling the voltage source converter acting as an interface between the solar PV panel and the utility grid. An optimal power extraction technique is applied to extract maximum power from the solar PV array. A fair comparison of the implemented discrete SOGI control algorithm with the existing continuous control algorithm is carried out. The performance of the implemented system is extensively evaluated by MATLAB/Simulink platform. The system’s performance is also tested for dynamic conditions of solar irradiance variation, different states for load variations to confirm the viability of the implemented control algorithm.