Stochastic Optimal and Robust Control Scheme for Islanded AC Microgrid

Abstract

This paper presents a stochastic optimal and robust control scheme for islanded AC microgrid (MG). Such AC MG is composed of multiple wind turbine generators (WTGs), photovoltaic (PV) units, fuel cells (FCs), micro turbines (MTs), diesel engine generators (DEGs), battery energy storage (BES) devices, flywheel energy storage (FES) devices and loads. Our purpose is to design a controller such that two targets are achieved: 1) the rational utilization of MTs, FCs, DEGs, BES devices and FES devices; 2) the regulation of the AC bus frequency deviation. Firstly, we consider the modeling of the islanded MG system. Considering the stochastic power change within renewable power generation devices, energy storage (ES) devices and loads, we formulate the system via a group of linear stochastic differential equations (SDEs) and ordinary differential equations (ODEs). Secondly, we formulate the problem of rationally utilizing MTs, FCs, DEGs and ES devices as the stochastic optimal control ( $\pmb{H}_{2}$ control) problem, and we formulate the issue of frequency regulation as the stochastic $\pmb{H}_{\infty}$ control problem. Thirdly, we present a mixed stochastic $\pmb{H}_{2}/\pmb{H}_{\infty}$ controller via the Nash game approach such that both our aims are achieved. Finally, numerical simulations are used to illustrate the effectiveness of the proposed design technique.