Control Methods of Inverter-Interfaced Distributed Generators in a Microgrid System

TLDR

Microgrids integrate renewable energy through inverter‑interfaced distributed generators, operating in grid‑connected or island modes, but abrupt mode changes and voltage/frequency variations can degrade performance. This study develops and optimizes controller designs to stably coordinate multiple inverter‑interfaced DGs and robustly control individual inverters against voltage and frequency disturbances. Droop‑control concepts coordinate the system, while control‑theoretic methods tune device‑level inverters, with optimal parameters obtained via particle‑swarm optimization. Simulation results confirm that the optimized parameters improve control performance, demonstrating stable coordination and robust disturbance rejection.

Abstract

Microgrids are a new concept for future energy distribution systems that enable renewable energy integration and improved energy management capability. Microgrids consist of multiple distributed generators (DGs) that are usually integrated via power electronic inverters. In order to enhance power quality and power distribution reliability, microgrids need to operate in both grid-connected and island modes. Consequently, microgrids can suffer performance degradation as the operating conditions vary due to abrupt mode changes and variations in bus voltages and system frequency. This paper presents controller design and optimization methods to stably coordinate multiple inverter-interfaced DGs and to robustly control individual interface inverters against voltage and frequency disturbances. Droop-control concepts are used as system-level multiple DG coordination controllers, and control theory is applied to device-level inverter controllers. Optimal control parameters are obtained by particle-swarm-optimization algorithms, and the control performance is verified via simulation studies.