Decentralized load frequency control using a new robust optimal MISO PID controller

Load Frequency Control (LFC) is one of the most important issues in electric power systems. Although Proportional-Integral (PI) controllers are commonly used for LFC systems in industry, they are unable to obtain good dynamic behavior in presence of various load changes and operating conditions because the PI controller parameters are usually tuned based on a classical or trial and error approaches. In this paper, a new decentralized robust optimal MISO PID controller based on Characteristic Matrix Eigenvalues and Lyapunov method is proposed as an appropriate technique for Load Frequency Control (LFC) problem. In the proposed method, the tuning of PID controller is stated as an optimization problem in which a combination of quadratic index and maximal complex/real ratio of the closed loop poles is minimized subject to some constraints on Characteristic Matrix Eigenvalues. The proposed method supports a tradeoff between acceptable and desired performance and robustness at the same time. To ensure the good performance of the method, it is applied to a control area which is linked to other control areas of an interconnected power system. This control area includes two large dams, namely, Karoon3 and Des hydro power plants in KHOZESTAN (a province in southwest of Iran). Simulation results confirm the efficiency and consistency of the proposed method. (C) 2011 Elsevier Ltd. All rights reserved.