Effect of distributed energy storage systems in the voltage stability of an island power system

In this work the author studies the effect of energy storage systems (ESS) used as distributed reactive compensation for voltage stability of an island power system. The dynamic voltage behavior using four load models was studied for these scenarios. The system under study was closer to voltage instability when loads were modeled using static load models than with load models considering induction motors, being the constant power load model the most critical. Modal analysis was performed to determine the system's weakest buses. V-Q curves were plotted for these buses to determine their reactive power margin. For our ESS, we consider the use of superconducting magnetic energy storage (SMES) technology as well as battery energy storage systems (BESS) and assumed the availability of four 15 MVA ESS units for reactive compensation. Six reactive compensation cases considering the allocation of all four SMES units at a single bus and their allocation distributed at different buses were evaluated. Cases considering one-site ESS location were able to increase bus voltages at one weak area, while the distributed ESS schemes managed to increase critical bus voltages at more than one weak area.