Hierarchical optimization technique for placement of battery energy storage system to improve transient frequency stability of a grid

Abstract

Battery energy storage system (BESS), due to its very fast dynamic response, plays an important role in improving the transient frequencystability of a grid.The performanceof BESS varies with its installation site in the system. Hence, the optimal location of BESS is of utmost importance for improving the transient frequency stability. Therefore, this thesis presents a hierarchical approach for optimizing the placement of BESS to improve the transient frequency stability of a grid. In most of the research, frequency nadir and rate of change of frequency have been considered for studying the frequency stability. This thesis considers two more parameters along with frequency nadir and rate of change of frequency to study the transient frequency stability, which are settling time and decay ratio. A novel frequency stability index (FSI) has been developed using thefour transient frequency parameters.After a large disturbance in an IEEE 9-bus test system, the FSI has been used to identify the optimal location of BESS in stabilizing the frequency.It has been observed that, after a sudden generator outage, the rate of change of frequency and the frequency nadir improve the best when BESS is located at the bus closest to the generator experiencing the outage.However, considering the other two parameters as well, the value of FSI is the minimum i.e. optimum with BESS located at the bus that is the second closest to the generator experiencing the outage.Results of similar studiesvalidate the proposed FSI in indicating the optimal location of the BESS in improving the transient frequency behaviour of the system.