Study On Nonlinear Coordinated Sliding Mode Control Of Power System With SVC

With the development of electric power technology, computer technology and control technology, the Flexible AC Transmission System (FACTS) appears which supply some new means to raise transmission capacity and improve power system stability. The static Var compensator (SVC) which is one of FACTS is an effective device to improve the transient stability, which has been proved.In recent years, more and more FACTS controllers are added to power system for improving system performance. However, these controllers have also increased power system complexity and uncertainty. Besides, their mutual effects become especially obvious between these subsystems, such as the FACTS controller and the excitation control system, the FACTS controller and the vapor valve control system, FACTS controller and FACTS controller. A multi-input nonlinear system which is composed of these controllers and the system must adopt advanced, reliable, good robust coordination control method to ensure this system safe and stable. Therefore, this thesis mainly studies on nonlinear coordinated sliding mode control of power system with SVC. The main contents have:Firstly, the FACTS technology is introduced and the basic structure and principle of static Var compensator is illustrated specially. The effect of static Var compensator on power system is analyzed deeply. Some functions are elaborated in detail, such as raising transmission capacity, improving power system stability, strengthening system damping, relieving system sub-synchronous oscillation, preventing the voltage fluctuation, optimizing HVDC transmission system performance.Secondly, the basic concept of the differential geometry theory is introduced. The exact linearization condition and the linearization process are analyzed on basis of SISO system and MIMO system, respectively. The basic principle of the sliding variable structure control is expounded. The design process and method is analyzed fully. A detail analysis on the vibration cause of the sliding variable structure control is made, and ways how to weaken vibration are discussed.Thirdly, a novel coordinated controller is proposed for SVC and excitation of a single machine linked to an infinite bus system. On the basis of differential geometry, the generator nonlinear SVC and excitation control system is putted up by combining the differential geometry theory with the vector variable structure control theory. At last, a novel coordinated controller is compared with excitation controller and SVC controller, respectively. Simulation results show that the novel coordinated controller gives better dynamic and good robustness.Fourthly, another novel coordinated controller is provided for SVC, excitation and steam valve of a single machine linked to an infinite bus system. On the basis of exact linearization geometry, the generator nonlinear SVC excitation and steam valve control system is exactly linearized via state feedback. The exact linearization system is controlled by using sliding model control based on Lyapunov direct method. At last, the novel coordinated controller is compared with tradition linear controller and nonlinear optimal control, respectively. Simulation results show that the novel coordinated controller gives better dynamic and good robustness.Finally, third novel coordinated controller is presented in the paper for Steam-turbine Generator excitation,steam valve and FACTS (TCSC/SVC) to improve the stability of power system which is a single machine infinite system. Firstly, the nonlinear mathematic modeling of the nonlinear FACTS, excitation and steam valve of the system is exactly linearized via state feedback. Then , the quasi- linearization system after exact linearization is controlled by sliding model control method. At last, simulation results show that the novel coordinated controller gives better dynamic response and stronger robustness.