Active Distribution Grid Management based on Robust AC Optimal Power Flow

Further integration of distributed renewable energy sources in distribution systems requires a paradigm change in grid management by the distribution system operators (DSO). DSOs are currently moving to an operational planning approach based on activating flexibility from distributed energy resources in day/hour-ahead stages. This paper follows the DSO trends by proposing a methodology for active grid management by which robust optimization is applied to accommodate spatial-temporal uncertainty. The proposed method entails the use of a multiperiod AC-OPF, ensuring a reliable solution for the DSO. Wind and PV uncertainty is modeled based on spatial-temporal trajectories, while a convex hull technique to define uncertainty sets for the model is used. A case study based on real generation data allows illustration and discussion of the properties of the model. An important conclusion is that the method allows the DSO to increase system reliability in the real-time operation. However, the computational effort grows with increases in system robustness. Index Terms — Decision-making; uncertainty; distribution system operator; robust optimization; solar power; wind power. NOMENCLATURE The main notation used throughout the paper is stated next for quick reference. Other symbols are defined as required. A. Parameters P ∆ Power deviation of the vertices of the uncertainty set , η η Ch Dch Charge and discharge efficiency B Imaginary part in admittance matrix Bus Number of buses C Cost BatCap E Maximum capacity of energy storage systems Min E Minimum energy in the energy storage system G Real part in admittance matrix N Number of unit resources T Time horizon y Series admittance of line that connects two buses sh y Shunt admittance of line that connects two buses