Robust Performance Satisfaction of DC Microgrids Using a Decentralized Optimal Voltage Control Strategy

Abstract

In this article, a decentralized scalable voltage control approach for islanded dc microgrids with a general structure is proposed. The microgrid system under study comprises several distributed generation (DG) units, every one containing an uncertain local ZIP [constant impedance (Z), constant current (I), and constant power (P)] load. We propose a voltage control strategy that ensures robust desired performance of the closed-loop islanded dc microgrid in addition to the robust stability under different uncertainty sources, including uncertain ZIP loads, topological changes, and plug-and-play functionality of DGs. The presented approach does not impose any restrictions on the dynamics of the distribution lines connecting different DG units. In the proposed control scheme, each local controller is the solution of a single convex optimization problem, which leads to the optimal performance of the dc microgrid. At first, an LTI state-space model with polytopic uncertainty is developed for islanded dc microgrid with different uncertainty sources. Then, a robust dynamic output-feedback-based controller with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\boldsymbol{H}}_\infty }$</tex-math></inline-formula> performance criterion is proposed for the satisfaction of all control objectives. The final obtained problem is turned into an LMI-based optimization problem. Different scenarios are simulated in MATLAB to affirm the feasibility and efficiency of the proposed control technique in the dc microgrids.