DC-link voltage stability enhancement in intermittent microgrids using coordinated reserve energy management strategy

Abstract

In recent years, due to its cost effectiveness and environmental advantages, demand for renewable energy resources has grown and their contributions to grid power has therefore increased while requiring effective frequency and voltage regulation. DC link voltage instability is a potential problem in solar energy microgrids, especially during an intermittency, where the system reliability degrades and DC link capacitor is under higher stress. In this article, a novel reserve energy management scheme based on battery and super capacitor storage is presented to stabilize the DC link voltage and reduce capacitor stress, while enhancing the system reliability. The scheme is tested in four different scenarios: Inverter connected DC-microgrid with irradiance intermittencies, standalone DC-microgrid without inverter and irradiance intermittencies, standalone DC-microgrid without inverter and load intermittencies, and standalone DC-microgrid with inverter under irradiance intermittencies. Simulation results indicate that the proposed control strategy stabilizes DC link voltage over all scenarios, even subject to large instances of irradiance or load changes. During low solar irradiance, the battery and super-capacitor promote voltage stability by compensating power deficits from the utility grid in the inverter connected grid case. In stand alone mode, the battery provides power during intermittencies and the supercapacitor provides fast transient voltage compensation. The strategy is notable in reducing stress on DClink capacitors and mitigating inverter voltage fluctuations, ultimately enhancing inverter longevity. The results show that the proposed control scheme can improve voltage stability, mitigate the transient effects and guarantee the reliable operation of solar microgrids in variable conditions.