Mathematical modeling and advanced control strategies for enhanced voltage and frequency regulation of grid-forming inverters

Abstract

With the rapid increase in renewable energy integration, conventional inverters are finding it difficult to maintain stable voltage and frequency. In contrast, grid-forming inverters actively regulate these parameters, providing enhanced stability and flexibility. This thesis explores the core advantages of grid-forming inverters comparing to conventional inverters, develops mathematical models for voltage and frequency control, and proposes advanced control strategies to handle various disturbances and intermittent power sources. Comparison of the simulation results confirms that grid-forming inverters could output power with higher quality and have the functionality to switch between on and off-grid mode compared to conventional inverters. Meanwhile, this thesis improves the virtual synchronous machine control method by embedding the integral term in reactive power control to achieve the voltage regulation with zero difference.