Grid Forming and Grid Following Control for Frequency and Voltage Stabilization of Hybrid Renewable Energy Systems in Microgrid

Abstract

This study presents a grid-forming (GFM) inverter designed for a battery energy storage system (BESS) to maintain voltage and frequency stability within an AC microgrid. The proposed GFM inverter plays a critical role in autonomously regulating voltage and frequency when the utility grid experiences failures or disruptions. Unlike grid-following (GFL) inverters, which rely on an external grid reference, the GFM inverter takes control during grid outages, forming a stable local grid by dynamically adjusting its output. This ensures uninterrupted microgrid operation, enabling seamless transition between grid-connected and islanded modes. The battery storage system, managed through the GFM inverter, supports frequency stabilization by balancing power fluctuations, thereby enhancing microgrid reliability and resilience. The AC microgrid network consists of a windgenerating system (WGS), photovoltaic system (PVS), BESS, three-phase utility grid, AC loads, AC/DC converters, and DC/DC converters. Maximizing power extraction methodologies augment energy production from both WGS and PVS. A GFL inverter employing active and reactive power regulation is executed with a Phase Lock Loop (PLL) and vector control methodology to achieve synchronization with the utility grid. The GFM inverter utilizes droop control to maintain steady voltage and frequency for effective grid integration. The system is validated using simulations under different scenarios, including the sudden implementation of WGS and grid failures. The rapid frequency response illustrates the efficacy of the proposed control approach. Simulation results provide a swift frequency response and maintain grid stability, validating its appropriateness for AC microgrids.