Grid-assistive use of private battery energy storage systems based on fuzzy logic

The energy transition is changing the structures of the electrical grid. The increasing number of decentralised energy generation systems, especially private photovoltaic (PV) systems, as well as high-power electrical loads in the low-voltage (LV) grid are leading to overloads at the local grid transformer in both power flow directions. This can lead to protection, reliability, stability and voltage quality problems. This paper investigates whether these overloads can be reduced by the grid-assistive use of private battery energy storage systems (BESS), which are installed in households in combination with a PV system. For this purpose, a real LV grid with a high density of PV systems is simulated. Fuzzy logic is used to develop a control system for the BESS installed in the grid based on a 24-hour power forecast. The results show that the control can reduce normal power peaks by up to 33.1% respectively reverse peaks by up to 16.1 % and fully utilise the storage capacity. When considering future grids, however, it becomes clear that the presented method does not offer a complete alternative to grid expansion, but rather enables a delay in grid expansion.