Cooperative Control of Power System Load and Frequency by Using Differential Games

Electric power systems are evolving toward smart grids all over the world, which are generally regarded as the next-generation power systems with extensive application of advanced control, communications, and computation techniques. More and more distributed intelligent controllers will be employed in smart grids. Load frequency control (LFC) is a key issue in the traditional interconnected power systems, which constantly requires different control areas (CAs) to share the regulation burden of the CA that lacks regulation capacity by providing the power supports via the tie-line. Such a process imposes extra regulation costs on the helping CAs, for example, the wear and tear of generating units, which may result in the unfairness and the CAs´ deviation from the LFC command. This situation becomes even more serious with the integration of intermittent renewable energy such as wind and solar power. In this paper, cooperative control by using differential games (DGs) is proposed as a possible solution to this problem. With a two-area and a three-area LFC models, a noncooperative equilibrium solution, and two cooperative equilibrium solutions with different time-consistency properties are derived. The case studies compare the proposed three DG-based LFC schemes with the traditional approaches based on proportional-integral control and the optimal control, and the results show that the cooperative control schemes allocate the regulation burden more rationally and ensure the CAs´ sticking to the LFC command, which will be favorable to the stability of power system operation. The capability of conflict solution of DG-based cooperative control makes it a very promising scheme for smart grid control.