Abstract
Numerous control methods based on modern control theory have been proposed to improve the load frequency control (LFC) characteristics of power systems. These control methods generally regard the load frequency control system as a linear system model. Furthermore, complicated mathematical equations have to be solved to determine control laws. However, realistic power systems are nonlinear, i. e., the nonlinearities of tie-lines connecting between the control areas and of generation rate constraints of power plants are existed. Consequently, it is considered that the design of controllers are difficult.
In this paper, the application of fuzzy control to the load frequency control system is proposed to solve the problems stated above. The proposed control first, to satisfy the load frequency control requirements, estimates power demand variations of the control areas and uses them as the output set-point values of power plants, instead of using an integral-type controller. Next, to improve stability and optimality of the nonlinear load frequency control system using the above output set-point control method, the proportional-type fuzzy control considering a computation time-delay is implemented. Parameters of the proposed fuzzy controller are determined by minimizing the integral square of the area control error (ACE) to assure optimality of the system.
