Control and Power Sharing of an Islanded DC Microgrid Integrating a Back-up Diesel Generator

Abstract

Originally proposed at the beginning of the twenty-first century, as a solution to electrify remote areas and integrate renewable energy sources to mitigate environmental pollution, Microgrids are gaining nowadays an increased interest, especially, DC microgrids. Many merits over AC grids, such as ease of control, higher efficiency and reliability make DC microgrid applications spread worldwide. Several researches address the control hierarchy and strategy in DC microgrids. On a local control level, Droop Control is a commonly used technique that ensures simultaneously DC bus voltage regulation and proper load sharing between operating converters. Yet, this paper investigates DC Microgrids control strategy from a different approach which is convenient, fundamentally, for remote islanded DC Microgrids. In such applications, the existence of the energy storage system (ESS) is substantial for a safe and stable Microgrid operation, especially, due to the intermittency and unpredictability of renewable energy sources (RESs) generated power. Hence, this paper proposes a simple, local control level, technique which is applied to a standard islanded DC Microgrid topology including: RESs, ESS and a back-up Diesel Generator (DG) as a traditional polluting source. The adopted control strategy main goal is to stabilize DC bus voltage, through ESS, and prevent battery excess discharge by connecting, temporarily, a back-up DG to the Microgrid as an additional source. When connected to the common DC bus, the DG takes charge of stabilizing the DC bus voltage. Once the power flow balance equation is reached again, the DG is disconnected instantly in order to reduce Carbone emissions. Finally, simulation tests are conducted in order to prove the viability and robustness of the proposed method.