Control strategy of frequency and DC voltage for interfacing converter of hybrid AC/DC microgrid based on improved virtual synchronous generator

Abstract

Integrating renewable resources in microgrids (MGs) poses a substantial challenge: ensuring stability with low inertia. This paper provides control techniques for the AC frequency and the DC voltage for an isolated/islanded hybrid AC/DC MG using intelligent virtual synchronous generators (VSGs) and intelligent virtual capacitors (VCs). The suggested approaches take advantage of VSG's adaptive damping coefficient and VC's adaptive virtual resistance as defined by intelligent controls. The controllers operate independently, relying solely on local DC voltage and AC frequency measurements without additional communication infrastructure. Compared to the traditional VSG and VC, the hybrid MG with intelligent VSG and VC controls performs better in suppressing AC frequency and DC voltage deviations, regardless of operating mode (rectifier or inverter). Simulation studies in MATLAB/Simulink validate these findings, showing that the artificial neural network (ANN) approach reduces DC voltage deviation by 34.4% and AC frequency deviation by 26.3%, while the fuzzy logic control (FLC) approach further reduces these deviations, particularly DC voltage deviation by 41.9% and AC frequency deviation by 23.2%. ANN excels in reducing deviations for AC frequency, while FLC is more effective in lowering deviations for DC voltage. The proposed controllers' positive impact on system stability is assessed using small-signal stability analysis.