Evaluating the trade-off between grid expansion and flexibility usage in electrical distribution grids

The increase of operational flexibility potential, provided by distributed energy resources (DER), might extend the distribution grid operators toolbox for congestion management beyond typically used measures such as grid expansion. However, the usage of grid expansion and flexibility measures are interdependent and their cost-minimal mix is unknown. Therefore, within the presented work, the trade-off between grid expansion and flexibility usage is investigated for three different coherent medium- and low-voltage grid structures. To evaluate the different degrees of grid expansion, multiple expansion variants are determined varying regarding their remaining thermal congestions. Subsequently, the optimal usage of flexibility to mitigate these remaining congestions is identified and the incurred costs are calculated. The investigations show that a sensible combination of both measures leads to cost optimal results. However, the optimal trade-off between grid expansion and flexibility usage is highly dependent on the grid structure. Within the rural grid, grid expansion measures can reduce the total costs by almost 80 %, whereas the usage of flexibility can reduce the total costs within the urban grid by 52 %.