Integration of battery energy storage with flexible AC transmission system devices

This dissertation, consisting of five papers, presents the results of research on the incorporation of battery energy storage into a Static Synchronous Compensator (StatCom). The main contribution of this body of work is the establishment of the modeling and control of the StatCom/BESS in power system dynamic applications. The first paper is focused on the steady state characteristics of the StatCom and StatCom/BESS. The characteristic curves of output voltage and output power were proposed and used in comparing the functionality of the StatCom and StatCom/BESS. In the second paper, a StatCom model was proposed and used in power flow analysis. The main advantage of new proposed StatCom model is that the StatCom switching losses and high frequency losses are considered and well represented using an equivalent resistor. This new model can be easily implemented in the traditional power flow program. The accuracy of the new model is verified by a detailed steady state simulation and dynamic simulation. The third paper introduced an integrated StatCom/BESS for the improvement of dynamic and transient stability and transmission capability. This paper compares the performance of different FACTS/BESS combinations, and provides experimental verification of the proposed controls on a scaled StatCom/BESS system. In the fourth paper, the conventional PI control for StatCom is compared and contrasted with various feedback control strategies. A linear optimal control based LQR control is shown to be superior in terms of response profile and control effort required. The fifth paper presents the Load Increase Index which is a new computationally efficient loadability index derived from the continuation power flow method. The proposed index is a by-product of the continuation power flow, and may be obtained with little extra computational effort, while yielding considerable information about the distance to the critical loading point. The mathematical relationship of the proposed index to two other cornmonly used voltage stability indices: the smallest singular value of the loadflow Jacobian and the determinant of the loadflow Jacobian are also presented in this paper.