A new optimal robust controller for frequency stability of interconnected hybrid microgrids considering non-inertia sources and uncertainties

Abstract

In this paper, a virtual inertia control based on a new optimal robust controller is proposed to improve the frequency stability of modern power systems considering renewables, nonlinearities, and frequency measurement effects. In applying the virtual inertia control technique, a phase-locked loop (PLL) is required to obtain the estimation of the system frequency data. However, the use of PLL can lead to greater system frequency fluctuation, and thus this problem will be aggravated with a lack of inertia in microgrids, which leads to system degradation and instability. Therefore, the proposed robust control technique is implemented based on a coefficient diagram method (CDM), which is designed optimally by a novel metaheuristic algorithm named chaotic crow search algorithm (CCSA). Where this proposed algorithm results from adding chaotic behavior to the crow search algorithm (CSA) in order to avoid suboptimal solutions and increase the convergence rate. Moreover, this study seeks to keep pace with smart future power systems by presenting a two-area interconnected hybrid microgrid (HMG) considering high penetration levels of renewable energy sources (RESs). Each HMG contains a thermal power plant, solar and wind power, electric vehicles (EVs), energy storage system (ESS), and customer loads. The superiority of the proposed control strategy (i.e., virtual inertia control based on the optimal robust CDM controller) is validated by comparing its performance with; conventional load frequency control (LFC) (i.e., integral controller), and virtual inertia control technique-based derivative control with/without the PLL. Moreover, the simulation results proved that the proposed control strategy could substantially endorse low-inertia multi-HMG for several contingencies.