Cost-effective Use of Flexible Resources for Voltage Support in Medium Voltage Distribution Grid

With higher electrification and presence of distributed renewable energy resources, over- and under-voltage are likely to occur more frequently. Power system flexibility is an active measure the distribution system operators (DSOs) can utilize to mitigate voltage issues, but their effectiveness and cost from activation must be considered. This work aims at capturing how flexible resources can provide cost-effective assistance to voltage issues in the grid. The method used creates an optimization model with AC optimal power flow (OPF) that includes flexible activation with a marginally increasing cost. The method finds the cost-effective dispatch of flexibility, both considering spatial effectiveness and the cost of flexible activation. This methodology is applied to a modified IEEE 33-bus test grid with several flexibility available. The results show how cost-effective activation is impacted by different cost curves for flexibility, where the marginal cost difference for increasing contribution affects where activation is deemed cost-efficient. With increasing under-voltage limit, a supply curve for flexibility on voltage support can be created from the results that considers the marginal cost of voltage support and activation volume. These supply curves can be incorporated towards market clearing principles to visualize the cost and price flexibility towards voltage support.