الفهرس | Only 14 pages are availabe for public view |
Abstract There has been continuing interest in designing load-frequency controllers with better performance during the past 3 decades. The usual design theory to develop control laws on the basis of the linearised mathematical model is used. In the application of optimal control techniques, the controller design is normally based on fixed-parameters. However, as the system parameters can not be completely known (or can be changed), controller design based on a fixed parameter model may not ensure the stability of the overall system if the real plant model differs from the assumed plant model. In this research two techniques are applied to design a supplementary load frequency controller (LFC) for power systems. The mathematical model used for LFC studies in this thesis considers parametric uncertainties represented by parameter deviations up to ±50 % from their nominal values. Moreover, a generation rate constraint for generating units is considered in the LFC model. The first controller developed in this research is a robust, fixed parameter controller designed using the standard Hco optimal regulator. The controller uses the frequency deviation of the system as a single feedback control signal. The second controller design is based on the Fuzzy logic concept. The controller inputs are the frequency deviation and its rate of change. The Fuzzy rules are deduced so as to simulate the Heo controller dynamic behaviour. Afterwards, some tuning is introduced to enhance the dynamic behaviour of the Fuzzy controller. The reliability of the proposed controllers is proved through a comparison of their responses to that of a Riccati-equation based robust controller.the design procedures for the two controllers are used to propose new strategies for the LFC of the Egyptian power system. To implement the Hco and Fuzzy controllers designed in this thesis, the program developed by the national energy control center (NECC) of the Egyptian Electricity Authority to design the load shedding scheme for the Egyptian power system is used. The Egyptian power system model was rebuilt using Matlab/Simulink without the load shedding modeL Since the NECC program considers only the effect of primary reserve concepts, a secondary loop based on a frequency signal is added to the Simulink program enable utilizing the effect of secondary reserve concepts. Case studies are carried out to evaluate the effect of the secondary control loop on the behaviour of the system frequency. The procedures applied for designing the Hco and the Fuzzy controllers are used. The two controllers are added one at a time to the Simulink model with the secondary controller. The obtained results prove better system performance with the added controllers. Finally, the two controllers (Heo & Fuzzy) are applied to a multiarea system obtained by interconnecting two hypothetical power systems with the Egyptian power system. The obtained results proved that the controllers exhibit an excellent performance. |