SECURITY OPTIMIZATION OF BULK POWER SYSTEMS IN THE MARKET ENVIRONMENT

The Chapter describes some applications of optimization procedures in the area of power system control, with attention to security in the market environment. In particular, the focus of the Chapter is on the reactive/voltage security. In the first Section, the authors will focus on the use of optimization methods to manage the reactive resources: the Optimal Reactive Power Flow (ORPF) problem will be introduced and analysed in detail, taking the minimization of power losses as reference. The goal of such procedures is to define voltage profiles suitable for the operation of bulk power systems in order to optimize both economy and security. In the market environment, due to a change of perspective, the minimization of power system losses could be no longer adequate; therefore, the authors developed some ORPF procedures adopting different objective functions (OFs) dealing with security. In the Section, such objective functions will be explained and the relevant issues described: the voltage collapse distance, different formulations of voltage stability indices derived from the Power Flow Jacobian, the role of the Secondary Voltage Regulation. These new approaches are dealt with adopting modern optimization techniques. The second Section will present the application of optimization technique based on the Interior point and Artificial Intelligence (in particular, Genetic Algorithms). Finally, the third Section will explain how, in a market environment, different points of view can be taken into account by the use of Multiobjective methodologies. They allow improving the security and reliability of power systems at the same time during the short-term planning and the operation. The possible use of several objective functions, the methods adopted to take into account the different (non inferior) solutions and the procedures that can be implemented to compare the non inferior operating points will be described. In particular, once the determination of the Pareto set of non inferior solutions is performed, some different methodologies are available in order to make the ultimate choice and to determine the final operating point for the system. This Section will present a review of these methodologies, with particular attention to the Worth Trade Off analysis.