الفهرس | Only 14 pages are availabe for public view |
Abstract Power systems are modeled as large-scale systems composed of a set of small- interconnected subsystems. It is generally impossible to incorporate many feed back loops into the controller design for large scale interconnected systems and is also too costly even if they can be implemented. These motivate the development of decentralized control theory where each subsystem is controlled independently on its local available information. On the other hand, the operating conditions of power systems are always varying to satisfy different load demands. Control systems are therefore required to have the ability to damp the system oscillations that might threaten the system stability as the load demand increases. However, as power systems are large-scale nonlinear systems in nature, the applications of conventional power system stabilizer (PSS) are limited. There is thus a need for controllers, which are robust to changes in the system operating condition. Robust controllers based on HeY;) control theory are particularly suited for this purpose. This thesis proposes two robust decentralized controllers for multimachine power system instead of using a complex centralized controller. The first one is based on H theory, and results in high order controller. The second controller is a 00 proportional integral (PI) type, and is tuned by a novel robust performance as the first one, but it is more appealing from an implementation point of view. In more detail, the second control design is first cast into the robust H control design in terms of 00 linear matrix inequalities (LMI) in order to obtain robustness against system operating conditions. An additional constraint is that the structure of the controller is predefined as a PI type, which is ideally practical for industry. In order to obtain the optimal controller parameters with regards to the H and controller structure constraints, . . 00 genetic algorithms (GAs), a powerful probabilistic search technique is used to find the control parameters of the PI controller. |