Research On Nonlinear Sliding Mode Control Of One Machine System With STATCOM

With the development of the control theory, electronical technologies and computer operation speed, more and more new technologies, new equipments and new strategies are applied into power systems. The Flexible AC Transmission System (FACTS) is a widely studied and applied one, which can effectively increase the transmission capability, enhance the transient stality of the power system and improve the quality. However, more FACTS 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. Consider that the power system is a typical nonlinear,variable structure,variable transformation parameter system. A multi-input nonlinear system which is composed of these controllers and the system's self must adopt nonlinear control method which with more robust to design the STATCOM controller.Static synchronous compensator (STATCOM) is a very important device of FACTS. The fundamental principle of STATCOM is the generation of a controllable ac voltage source by voltage source inverters connected to a capacitor. In this way, STATCOM can provide smooth and rapid reactive power compensation to power system which can maintain the bus voltage satability of the device setting point. Meanwhile, it's also can damper the power oscillation,improve transient stability limit. In contrast with static VAR compensator (SVC), STATCOM with faster response, better control stability, lower harmonics, and smaller size, etc. Therefore, this thesis mainly studies on nonlinear coordinated sliding mode control of power system with STATCOM. The main contents have:Firstly, the FACTS technology is introduced and the basic structure and principle of Static Synchronous Compensator is illustrated specially. The reactive current properties of STATCOM and the effect of STATCOM on transmission system statbility have been analyzed thoroughly.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. An analysis to the guasi variable structure control theory is given and which is used in this paper.Thirdly, a novel coordinated controller is proposed for STATCOM and excitation of a single machine linked to an infinite bus system. On the basis of differential geometry, the STATCOM and generator excitation nonlinear control system is putted up by combining the differential geometry theory with the guasi variable structure control theory. At last, a novel coordinated controller is compared with excitation controller and STATCOM controller, respectively. Simulation results show that the novel coordinated controller gives better dynamic and good robustness.Fourthly, another novel coordinated controller is provided for STATCOM, excitation and steam valve of a single machine linked to an infinite bus system. On the basis of exact linearization geometry, the STATCOM and generator excitation and steam valve nonlinear 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.