Load following operation of NAS battery by setting statistic margins to avoid risks

Among various types of battery energy storage systems (BESSs), NAS battery is the most promising products. NAS battery is a commercial product implemented widely in the world. The first purpose of BESS was improvement of load factors. The second purpose is improvement of power quality, especially against voltage-sag. The recent interest is oriented to utilize BESS to mitigate the intermittency of renewable energy. NAS battery has two types of operation mode. The fixed pattern operation mode operates BESS by the scheduled pattern that is determined in advance. This mode is not flexible, but there are no risks of shortage/surplus of battery. The load following operation mode operates BESS according to the real-time variable load. This flexible mode assists load control by energy managers. However, there are risks of shortage/surplus of battery. A control method of load following operation which uses statistic margins is proposed in this paper.