The Decentralized Control For Steam Valve Opening Of Time-delay Multi-machine Power Systems

ABSTRACT: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 HVDC and 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 it’s 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 addition, time-delay and various uncertainties are very common to interconnected large-scale system. For these reasons, 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 detail results are list as follows:1. The delay-independent robust decentralized controller and delay-independent controller based on interconnected observer are proposed while all the states are not completely measurable. After the nonlinear interconnected function is converted into a bounded quadratic inequality of the subsystem states, In addition, LMI sufficient conditions of asymptotical stability of closed-loop system or augmented closed-loop system are derived via the proper choice of Lyapunov-Krasovskii function. At the same time, the solving algorithm of each gain matrix is presented. 2. The two delay-dependent robust decentralized controllers and one delay-dependent controller based on interconnected observer are put forword to while all the states are not completely measurable. Two LMI sufficient conditions of robust asymptotical stability of the closed-loop system and one sufficient condition of asymptotical stability of the augmented closed-loop system are derived via the state transformation whose stability is equivalent to the original system states and the different choice of Lyapunov-Krasovskii function from the ones the common delay-dependent condition are used. In addition, the solving algorithm of each gain matrix is presented and the upper delay-time of eache subsystem is obtained at the same time. Furthermore, the derived delay-dependent stabilized conditions are easier and more convenient to solve than the common ones.3. The delay-independent and delay-dependent robust decentralized controllers are discussed considering sector saturation actuator. Because it must make more serious influence on a system when the two nonlinearities of time delay and saturation exist simultaneously. To this status, one delay-independent LMI sufficient condition and two delay-dependent LMI sufficient conditions of robust asymptotical stability of closed-loop system are derived via the proper choice of Lyapunov-Krasovskii function. In addition, the design algorithm of each gain matrix is presented.4. The delay-independent and delay-dependent robust decentralized controllers of steam valve opening in Lurie-type time delay multi-machine power system which is composed of steam turbo set with non-reheater are put forward to. Two delay-independent LMI sufficient condition of robust asymptotical stability of closed-loop composed large-scale system are derived when single delay and multi-delay are considered respectively. Furthermore, two delay-dependent LMI sufficient condition of robust asymptotical stability of closed-loop composed large-scale system are deduced via state transformation whose stability is equivalent to the original states and the proper choice of Lyapunov-Krasovskii function when single delay and multi-delay are considered respectively. In addition, the solving algorithm of each gain matrix is presented.From the Matlab simulations in two-machines infinite bus, it can be easily seen that the presented control schemes are efficient and permits the rapid stability of the closed-loop system. The comparisons with the ones without exerting any controller show that it is of great significance to the study of steam valve opening control of time delay multi-machine power system in this thesis. In addition, the upper time delay increases indeed by introducing the slack variables.