Mixed-Integer Nonlinear Optimal Power Flow for Congestion Management in Distribution Grids With Renewable Energy Resources

This paper presents an optimal power flow that enables the curtailment of active and reactive power of decentralized power plants in discrete and continuous levels, as well as the HV/MV-transformer tap changer, which is employed as part of congestion management. The resulting mixed-integer nonlinear optimization problem is solved using an outer approximation method. The calculation is subjected to analysis on two distinct bottlenecked MV-grids. For each, the impact of three distinct curtailment severities is examined. Considering further degrees of freedom, such as reactive power control of generation plants and tap changer control, allows to reduce redispatch costs and curtailed energy. The influence of finer curtailment levels on active power control depends on the topology of the grid and the number of plants. A comparison between mixed-integer and real-valued optimization problems shows the influence on performance of both optimal power flows.