DEVELOPMENT OF AN ADAPTIVE VIRTUAL SYNCHRONOUS GENERATOR-BASED FREQUENCY CONTROL STRATEGY FOR HYBRID AC/DC MICROGRIDS

Abstract

The rapid transition to sustainable energy sources has led to the large-scale integration of renewable energy technologies such as solar and wind power into today's power grids. These renewable resources do not generate mechanical inertia like conventional synchronous generators; the grids increasingly risk becoming more unstable when frequencies drop. This is particularly challenging in hybrid AC/DC microgrids, where both AC frequency and DC-link voltage must be controlled simultaneously, and Virtual Synchronous Generator (VSG) control is an efficient solution. A control algorithm is implemented to make inverters behave like the inertial and damping characteristics of a synchronous machine. However, most current VSGbased schemes use fixed values for virtual inertia and damping, which fail under varying disturbance magnitudes. Deviating from a fixed inertia value, this research designed and tested an adaptive VSG-based frequency control method for an isolated hybrid AC/DC Microgrid in MATLAB/Simulink R2024b. Real-time frequency deviation and rate of change of frequency (RoCoF) parameters are used to adapt the VSG frequency control. The interlinking converter was tested under two different load disturbances of opposite nature of 2s, i.e., load decrease and load increase, and compared with the conventional fixed-inertia controller (H = 0.5 kg·m²). In both scenarios, the inverter was found to be electrically stable, and the adaptive inertia was found to be sensitive to each disturbance, showing that it changes its operating condition from 0.5 kg·m² to approximately 0.6 kg·m² instead of remaining fixed; importantly, in each load change scenario, it was observed that the adaptive VSG performed a reduced transient frequency deviation than the conventional controller.