An Application Study Using Unified Power Flow Controller In Gansu Power System

On the basis of synthetically calculating and analyzing the power load characteristics of Gansu Power Network and the 330kv power flows of superhigh voltage power net operating in typical way, the author of this thesis points out the main problems existing in Gansu Power Network. By using the UPFC's research result and its control means, it is supposed to install UPFC on part of Gansu Power Network in order to improve the power transmission capacity, optimize power flow, mediate power block access, and prevent bus voltage to be overlimited. As a result, the power net will be more flexible, the power operation will be safer, and Gansu Power Network will really become the power exchange hub in the North-west of China.As the nature of power system is nonlinear, and UPFC itself is a nonlinear subsystem controlled by many variables, this thesis sets forth the methods and principles of UPFC's cascade compensation, transformation, voltage regulation and parallel connection compensation. On the design of control regularity, the thesis focuses on main control objectives, brings up the design of adopting simple and reliable RGA (Relative Gain Array) to decouple, determining best variables matching relations, and simplifying the control regularity of UPFC. In view of local measurements on implication and control of UPFC, the control mode of reactive currents control and voltage injection should be used.According to the constraint relations among the active powers and reactive powers at the end system, and bus bar voltage, the thesis draws a diagram of voltage on transmission lines—active curves and voltage—reactive curves. It also analyses the system stability and security when the transmission lines reach the power limit under the action of UPFC.Finally, the design is emulated with MATLAB by installing UPFC on the superhigh voltage line between the West Substation of Lanzhou and the Yincheng Substation, and on the superhigh voltage biloop-line between Pingliang Power Plant and Dingxi Substation. Unnecessary loop currents are cut off when UPFC transformation function is adopted. When UPFC transformation and adjustment functions are used, power limit on the transmission current successfully breaks through the voltage fall limit and improves the heat limit power on the transmission current. The result of emulation confirms the author's assumption and the efficiency of the UPFC control system. Therefore, this technology has a great significance bothon theory and on practical implication, and will provide technological support and aid on program, design and security dispatch for Gansu Power Network.