Sizing and optimization of battery energy storage system for wind and solar power plant in a distribution grid : A case study on optimizing the size of the battery for peak shaving and ancillary services

The increasing demand associated with the growing population poses a challenge to the operation of electricity systems worldwide. The electrification of the transport sector, accelerated electrification of industries and use of power demanding appliances in everyday life has increased the electricity demand significantly. With these challenges, the climate change is making the problem even more acute. To deal with climate change and other environmental problems resulting from the use of fossil for energy, renewable energy sources (RES) are predicted to play an important role. Clean and environmentally friendly sources are abundant in nature. These sources are highly dependent on weather which results into intermittency and variability in the electricity generation from them. High penetration of RES in a power system increases the uncertainty in the electricity supply. This exacerbates the need to balance the load and supply. A power system with high RES penetration might witness hours with high renewable power production, which might exceed the load. This is in addition to the peak load hours witnessed by the system. A potential solution to the problem is using battery energy storage system (BESS) to shave the load peaks the load peaks and store the surplus electricity from RES when needed. This project studies a system with and without the local generation by wind and solar power plants. In order to estimate the optimal size of the BESS, a threshold-base strategy is implemented, and the comparison is made based on the results of both systems. Whereby, 3% of the corresponding load peak is shaved. On-grid generation also contributes to the self-sufficiency of the grid in terms of total electricity consumption and leads to lower the overall peak supply from the transmission grid by about 5%. A study about revenue generation from participation of the BESS in the frequency market is also made, and the economic benefits are investigated. As a result of the study, a revenue of 34.5 million SEK can be generated during one year by participating in the frequency market.