A Robust Decentralized Power System Load Frequency Control

This paper presents a new robust decentralized controller based on mixed H2/H∞ control technique for the solution of Load Frequency Control (LFC) in a deregulated electricity environment. To achieve decentralization in each control area, the connections between this area and the rest of the system and the effects of possible contracts are treated as a set of new disturbance signals. It is shown that, subject to a condition based on the structured singular value (μ), each local area load frequency controller can be designed independently so that stability of the overall closed loop system is guaranteed. In order to minimize effects of load disturbances and to achieve desired level of robust performance in the presence of modeling uncertainties and practical constraints on control action the idea of mixed H2/H∞ control technique is being used for the solution of LFC problem. This newly developed design strategy combines advantage of H2 and H∞ control syntheses and gives a powerful multiobjectives design addressed by the Linear Matrix Inequalities (LMI) technique. To demonstrate the effectiveness of the proposed method a two-area restructured power system is considered as a test system under different operating conditions. The results of the proposed decentralized controller are compared with the conventional PI and pure H∞ controllers and are shown to minimize the effects of load disturbance and maintain robust performance in the presence of specified uncertainties and system nonlinearities.