Real-time Corrective Control in Active Distribution Networks

The continuous growth of renewable energy injected into Medium-Voltage (MV) distribution systems is expected to create new operational problem such as over- and under-voltages and/or thermal overloads of equipment. Therefore, the need for real-time corrective control will go increasing, since reinforcing the network to deal with these temporary situations is seldom an economically viable option for the Distribution System Operator (DSO). This requires monitoring the system through an appropriate measurement and communication infrastructure and taking control actions if the system is going to exceed its prescribed operational limits.
In this thesis, number of methods and algorithms have been devised, developed and tested which can allow DSOs to enhance the real-time monitoring and control of their grids, taking into account various practical challenges. The main components taking part in these corrective actions are Dispersed Generation Units and the transformer Load Tap Changer in the main sub-station. A centralized control architecture is chosen mainly for its capability of coordinating multiple control actions. Furthermore, the scheme is extended to a two-level structure in order to combine a fast but partial correction by the local controllers, followed by the smooth, coordinated control of the centralized one. Another extension deals with enabling the controller to contribute to LV network voltage corrections by adjusting voltages on the MV side of the MV/LV transformers where a voltage problem has been detected.
Finally, the time frame of the centralized controller is extended with preventive security restoration. The latter uses near-future production/consumption predictions to determine if the active distribution network is going to operate within prescribed limits and, if not, to determine appropriate preventive decisions that can be used, for instance, as reference for the real-time corrective controller.