Multiple roles coordinated control of battery storage units in a large-scale island microgrid application

In order to build a large-scale island microgrid with 100% penetration intermittent photovoltaic power generation as the only power source, a structure with multiple role battery energy storage systems (BESSs) is proposed in this paper based on the analysis of energy storage demand in the island microgrid and performance comparison of two types of batteries. The storage system in the proposed structure is composed of three types of functional BESSs. In detail, the master control units (MCUs) with LiFePO4 batteries are responsible for the voltage and frequency stability and instantaneous power balance, slave storage units (SSUs) with lead-acid batteries are responsible for daily energy storage, and multi-function units (MFUs) with LiFePO4 batteries are used for short-time energy regulation. A hierarchical control structure is adopted in the system. At the local level, the converters of the MCUs are controlled as the voltage sources in paralleled mode as grid-forming units, and those of SSUs and MFUs are controlled in the current source mode as grid-feeding units. At the system level, a real-time power balance coordinated control strategy is proposed, which has the capability of efficient and orderly operation of different types of BESSs. Simulation and practical operation analysis of the Qumalai 7.023MW microgrid demonstrate the practicality and effectiveness of the research methods of the island microgrid. (c) 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.