Optimal Frequency Regulation in AC Mobile Power Grids Exploiting Bilinear Matrix Inequalities

Abstract

By day-to-day improvement in a microgrid (MG) control, frequency regulation in the shipboard alternating current (ac) MGs has received much interest in the past decade. The shipboard MGs involve renewable energy sources (RESs) that are unable to produce reliable and constant energy. This important fact vividly demonstrates the requirement of modern frequency regulation techniques. This article proposes a novel dynamic output feedback controller (DOFC) for load frequency control (LFC) in a sample shipboard MG. The considered ac MG involves fuel cell, gas turbine, and diesel generator as the controllable power generators; photovoltaic array and sea wave energy converter as the renewable energy sources; and batteries and flywheels as the storage units. The existing approaches almost exploit linearization for solving the problem, which imposes restrictions on the problem and raises conservative constraints resulting in shrinking the solution space. This article suggests a simple approach that effectively reduces such limitations through the formulation of sufficient conditions on the controller design in the form of bilinear matrix inequalities (BMIs). This consequences in a more exact solution compared to the previous methods. To show the merits of the developed approach, OPAL real-time (RT) simulations are executed, and the results are compared to the other state-of-the-art-methods that prove the efficacy of the suggested approach. Also, the results of our proposed method (DOFC; <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n=2$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n=3$ </tex-math></inline-formula> ) are compared to the typical <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathrm {H}_{\infty }$ </tex-math></inline-formula> optimization, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mu }$ </tex-math></inline-formula> -synthesis, fuzzy type-1, and intelligent-PI methods. The comparisons between norms of the frequency deviation verify the efficacy of the proposed controller in this article.