A Decentralized Power Allocation Strategy for Dynamically Forming Multiple Hybrid Energy Storage Systems Aided With Power Buffer
Jialei Su, Kang Li, Li Zhang, Xuejiao Pan, James Yu
Abstract
Multiple hybrid energy storage systems (HESSs) consisting of batteries and super-capacitors (SCs) are widely used in DC microgrids to compensate for the power mismatch. According to their specific energy and power characteristics, batteries and SCs are used to compensate low-frequency and high-frequency power mismatches, respectively. This paper proposes a decentralized power allocation strategy for dynamically forming multiple HESSs aided with a novel power buffer. The power buffer is a device combing a capacitor and a bidirectional DC-DC converter, it is used as an interface between the batteries and DC bus, allowing easy Plug-and-Play of different energy storage units and effective and efficient power allocation. First, the power buffer and SCs split the power mismatch into a low-frequency and high-frequency part with a modified I-V droop control. Then the power buffer transfers the low-frequency mismatch to the batteries for compensation based on their respective state-of-charges (SoCs), while the high-frequency part is dealt by the SCs directly. This new scheme further allows elimination of the DC bus voltage deviations. Finally, the real-time hardware-in-loop (HIL) tests of three case studies confirm the effectiveness of the proposed control strategy.