A cooperative distributed droop gains adjustment in DC microgrids

Abstract

Direct Current (DC) microgrids are a very promising solution to integrate renewable energy sources, energy storage systems and loads. The main goals of a microgrid controller are to achieve voltage regulation and load sharing among multiple distributed generators (DGs). Distributed control techniques are widely adopted to address these two objectives. Most of the existing distributed methods in the literature adjust the deviation caused by the conventional droop control by adding two additional terms. In this work, a new cooperative distributed controller to adjust the droop gains of DGs is proposed. The proposed method achieves average voltage regulation and proportional current sharing in a unified manner. It does not require additional corrective terms, resulting then in a simple control structure. Moreover, it relies only on exchanging one communication variable among neighboring DGs, which reduces the communication overhead. The stability of the proposed controller is analyzed using a small signal model of the system. The effectiveness of the proposed controller is evaluated under common load changes, local load variations, communication link failures and communication delays. The designed control scheme is verified through Hardware-In-the-Loop (HIL) tests using NI PXIe real-time simulator.