Combined Grid-supporting and Market-based Operation Strategy for Battery Storage Systems

The growing supply from renewable energy systems (RES) into the distribution grid is leading to overloading of the existing grid lines. In that regard, battery storage systems (BSS) could be used to prevent power line overloading. If operated optimally, the BSS could buffer the high supply from RES and fulfill the (n-1) criterion replacing hence otherwise required grid expansion measures. In addition to the technical ability of the BSS, the cost efficiency of such an application must be verified. This paper proposes a new application strategy combining a grid-supporting and marketbased operation of the BSS. The approach proposed determines, in a first step, the optimal dimensioning and operation plan of grid-supporting BSS in combination with a dynamic curtailment of RES to prevent grid congestion and ensure the (n-1) criterion. This approach has been applied to a real German 110 kV grid over a period of one year. In a further step, the BSS dimensioned were integrated into the EPEX spot market in order to generate revenues at times when no grid congestion is forecasted. The total costs of the grid-supporting use of BSS and dynamic power curtailment less the gains from the electricity market were then calculated and compared to the costs of the real planned grid expansions.