Nonlinear Multi-Agent Optimal Load Frequency Control Based on Feedback Linearization of Wind Turbines

Large scale power systems have distributed structure since power generation units are distributed in the network. In such systems, where the communications are sometimes imperfect, centralized control structures have concerns to be applied. For such inherently distributed systems, multi-agent control structures are more appropriate. On the other hand, power systems have nonlinear dynamics. When all generation units are synchronous generators, linear approximation of swing equation of generators is a common choice. However, by penetration of renewable energy generation units, those have highly nonlinear dynamics, nonlinear control approaches should be applied. In this paper, a nonlinear multi-agent feedback linearization approach is adopted for optimal load frequency control of a power system with wind generation units. Multiagent controllers with both distributed and decentralized structures are proposed. Centralized feedback controller is also applied for comparison purposes. The parameters of the controllers are optimized using gray wolf optimization algorithm to improve time response of the system and reduce generation costs. IEEE 30-bus system with six synchronous generators and four wind turbines is considered as a test system. Simulation results verify the inefficiency of centralized controller and show that distributed control structure can produce a balanced performance in terms of time response and is better from the cost reduction view point than the decentralized controller.