An intelligent based LQR controller design to power system stabilization

This paper presents an intelligent model, named as free model, approach for a closed-loop system identification using input and output data and its application to design a power system stabilizer (PSS). The free model concept is introduced as an alternative intelligent system technique to design a controller for such dynamic system, which is complex, difficult to know, or unknown, with input and output data only, and it does not require the detail knowledge of mathematical model for the system. In the free model, the data used has incremental forms using backward difference operators. A linear transformation is introduced to convert the free model into a linear model so that a conventional linear controller design method can be applied. Also. it is shown that the free model is controllable, observable. and robust to disturbance. In this paper, the feasibility of the proposed method is demonstrated in a three-machine nine-bus power system. The linear quadratic regulator (LQR) method is applied to the free model to design a PSS for the system, and compared with the conventional PSS and LQR controller based on the ARMA-model. The free-model based (FMB) PSS is robust in different loading conditions and system failures such as the outage of a major transmission line or a three phase to ground fault which causes the change of the system structure. (C) 2004 Elsevier B.V. All rights reserved.