Research On H_∞ Control For Steam Valve Opening Of Multi-Machine Power System Based On T-S Fuzzy Model

Multi-machine power system is known as a complex interconnected large-scale system that is composed of many electric and electronic devices and mechanical components. At the same time, the structure and the model of the systems become more complicated, and many uncertain factors are brought to the system because of the application of high-voltage direct current (HVDC) and flexible alternating current transmission systems (FACTS), the interconnection of the area power systems, and the open of the electric power market. These make the grid structure be complex increasingly, so is the dynamic behaviour. Thus, it’s necessary to exert some control on the power system to improve its stability and dynamic level. It’s well known to us that it’s of great significance to enhance the stability level of power system that the research on the steam valve opening control of steam turbo set, which improves the stability with the big disturbance, as well as the stability with small disturbance and low-frequency oscillation and etc.In actual operation of power system, all kinds of uncertainties of the system lead to the changes of system parameters. Therefore, the actual multi-machine power system is difficult describe with accurate mathematical model. Restricted by the environment and the relevant conditions, not all state variables are available. In addition, due to various signals of the quantitative factors such as collection, processing and transmission is not timely, time-delay is widespread. Based on these, the thesis emphasises on the investigation on steam valving opening control in time-delay interconnected nominal or robust multi-machine power system which is composed of steam turbo set with non-reheater.The thesis first presents a dynamic model of the opening of the valve control of multi-machine power system, and then the fuzzy model is established in view that the characteristics of the actual power system is difficult to describe with accurate mathematical model. Observer-based decentralized control for the opening valve of multi-machine power system is studied, and controllers are designed based on LMI, considering the parameter uncertainty of system. Then in terms of network-based interconnected power system, network communication transmission between control areas is treated as packets form according to the actual amount of the network communication protocol, and control of network-based interconnected power system with time delay is investigated adopting the idea of network control. A controller is given to make the closed-loop system asymptotically stable considering the problem of actuator fault. Finally, stability conditions of multi-machine power systems with mixed time-varying delays are studied. The mixed time-varying delays include the interval retarded-type discrete delay, the neutral-type discrete delay and the time-varying distributed delays. Linear matrix inequalities (LMIs)-based stability conditions are derived to guarantee the H∞ performance. The simulation examples for interconnected power system show the effectiveness of the given method.