Distributed Secondary Voltage and Frequency Restoration Control of Droop-Controlled Inverter-Based Microgrids

TLDR

The paper addresses simultaneous voltage and frequency restoration in droop‑controlled inverter‑based islanded microgrids. A distributed finite‑time voltage control and a consensus‑based frequency control are implemented on local DGs, enabling reference convergence without a central controller. The distributed strategy restores voltage and frequency to reference values with accurate real‑power sharing under a proven local stability condition, as validated on a four‑DG MATLAB test system.

Abstract

In this paper, restorations for both voltage and frequency in the droop-controlled inverter-based islanded microgrid (MG) are addressed. A distributed finite-time control approach is used in the voltage restoration which enables the voltages at all the distributed generations (DGs) to converge to the reference value in finite time, and thus, the voltage and frequency control design can be separated. Then, a consensus-based distributed frequency control is proposed for frequency restoration, subject to certain control input constraints. Our control strategies are implemented on the local DGs, and thus, no central controller is required in contrast to existing control schemes proposed so far. By allowing these controllers to communicate with their neighboring controllers, the proposed control strategy can restore both voltage and frequency to their respective reference values while having accurate real power sharing, under a sufficient local stability condition established. An islanded MG test system consisting of four DGs is built in MATLAB to illustrate our design approach, and the results validate our proposed control strategy.