Operation of a Standalone Microgrid With an Advanced Discrete Generalized Integrator Based FLL Control

Abstract

This paper deals with an advanced discrete generalized integrator frequency-locked loop (DGI-FLL) control algorithm designed for regulating grid-side converter (GSC) of doubly-fed induction generator (DFIG). Its primary function is to ensure consistent regulation of DC-bus voltage of rotor side converter (RSC) and GSC. Notably, this advanced DGI-FLL control demonstrates robust performance even amidst fluctuations in wind speed and varying loads. By implementing advanced DGI-FLL control, notable enhancements in system dynamics such as improved rise time, delay time, and settling time are achieved across diverse load conditions. Furthermore, this control algorithm effectively addresses power quality (PQ) concerns associated with DFIG. Synchronization of DFIG stator windings with local grid is a pivotal aspect, with local grid established through a combination of a battery and a double-stage photovoltaic (PV) supported grid forming converter (GFC). Initially, open-circuit voltages and frequency are generated across stator windings of DFIG via stage-I RSC control. Subsequently field-oriented control (FOC) algorithm takes charge of RSC post-stator synchronization. This algorithm not only fulfills reactive component requirement of DFIG but also maximizes power extraction from wind turbine. Moreover, an energy storage system (ESS) based on batteries is integrated to store surplus energy and subsequently distributes it based on load demand. This paper presents comprehensive test results showcasing integrated performance of hybrid microgrid at varying load conditions, solar insolation and changes in wind speed. Notably, it demonstrates how total harmonics distortion (THD) for both current and voltage at point of common coupling (PCC) adhere to the standard set forth by the IEEE 519-2022.Std.