Operative factors affecting energy balancing and speed of equalization in battery storage system

Abstract

Energy storage systems play a significant role in power management systems and control of the modern grid. One of the most challenging issues is controlling storage units in distributed form. This paper presents a possible means of controlling Energy Storage Systems (ESS) through a decentralized approach. Moreover, the balancing and equalization of stored energy in different storage units presents other challenges in such systems; to deal with this, the paper discuss here the factors that affect energy balancing and the speed of the energy balance convergence. A Proportional-Integral (PI) controller is used in the upper control level to generate an accurate reference value for the State of Charge (SoC), and a modified droop control is employed on the lower control level to equalize the energy on the basis of the SoC. To evaluate the control algorithm and to investigate the factors that affect the speed of equalization, this paper considers the result of a case study with three battery storage units.