Energy storage system in the medium-voltage network

The distribution network in Germany is due to the rapid expansion of renewable energies the most affected part of the electrical power system. The behavior of the load flow in the medium and low voltage levels, especially through the feed of photovoltaic systems, is completely changing. The power supply from the overlaid voltage levels is subject to stronger fluctuations, which are mainly depending on weather conditions. The consequence is that higher power gradients can be expected at the supplying transformer. These can in turn be mastered by only a few types of power plants or be carried out very costly. With the use of central energy storage (CES), these power fluctuations are smoothed. Depending on the size of the storage peak shaving or even load leveling can be achieved. In this paper, the application of a central storage is presented in a rural distribution network, which has a high penetration of photovoltaic systems. The fluctuating feed of these solar power plants is considered with a measuring data set of several years which has a resolution of quarter-hour values. The centrally installed storage system has been simulated with different storage sizes. For the determination of results load flow calculations were performed with load profiles for a whole year in a quarter-hour resolution.