Abstract
Applications of Battery Energy Storage Systems (BESS) in the power grids will be expanded in the coming years due to factors such as decreasing costs of such systems. In a modern power network, BESS systems can be optimally controlled for peak-load shaving and other ancillary services such as volt-var control, system balancing and loss reduction. However, all these "system-level" controls will depend on the capability of each individual BESS to independently control the active and reactive power injection/absorption at its connected bus, and to maintain the voltage of the DC link between its AC/DC and DC/DC converters. As a result, understanding the behavior and control requirements for the operation of the BESS is necessary. In this paper, an active AC/DC rectifier and a bidirectional DC/DC converter have been modeled and analyzed for charging and discharging of the batteries in a BESS system. The models used in these analyses have been developed based on an integrated state-space equation set for the converters and the battery. This type of modeling is proper for demonstration of the effects of massively integrated storage systems in the bulk power grids.