Study of a battery energy storagesystem in a weak distributiongrid

The awareness of the problems with fossil energy sources have increased the past decades. To decrease the effects of the fossil fuels on the climate and the environment, the use of intermittent energy sources such as solar- and wind power are increasing. Intermittent generation creates instability in the power grid, which cause fluctuations in the voltage and the frequency of the power grid. To be able to handle these fluctuations, regulating capacity such as for example pumped storage or batteries are needed. This thesis has investigated how the placement and the power capacity of a battery energy storage system affects the possibility for frequency and voltage regulation in a weak distribution grid. The investigation was made in MATLAB Simulink by creating a weak radial distribution grid with a high penetration of solar power. The distribution grid had variable loads with different power consumption at each bus, creating instability in the distribution grid. The optimal placement of a battery energy storage system is firstly at the largest load and secondly as far away from the other power generation units as possible. A battery storage with a power capacity that can handle all consumption is optimal. It is possible to have a smaller power capacity if the grid is stable enough to withstand the appearing fluctuation of frequency or voltage. The frequency variations are more dependent on the power capacity and the voltage variations are more dependent on the placement of the battery energy storage system. ISSN