Research On Application Of Controllable Shunt Reactor In Ultra-high Voltage AC Transmission Lines

The operating characteristics of ultra-high voltage (UHV) alternating current (AC) transmission line are different from extra-high voltage (EHV) and high voltage (HV) transmission line. Reactive power balance and voltage control are very important research contents of UHV AC transmission line. The shunt reactor which is used to solve these problems is uncontrollable, it can't change the power smoothly and bring negative effects to the line when transmission power change constantly. Controllable reactor of transformer type (CRT) is one kind of controllable reactor, it has many characteristics as follows:big capacity, small harmonics, changing its power fleetly and smoothly, increasing the capacity of power transmission and voltage level, improving the flow distribution, restricting the over-voltage and sneaking current, boosting the stability of power transmission system and so on. This thesis is aimed at researching on how we can make the CRT used in UHV transmission line and operating characteristics of the line before and after the installation of CRT.The original parameters of UHV transmission line are analyzed and studied, and the formula for calculating conductance of unit-length line is established by experimental numerical method. Based on the equivalent circuit of unit-length line, calculating formulas of parameters inΠ-type equivalent circuit of UHV line with distributed parameters considered accurately are obtained, meanwhile, the simulation model with dialog box is established under the environment of MATLAB/SimPower Systems. Characteristics of the line without CRT such as voltage and current along the line, power frequency overvoltage, reactive power and so on are analyzed in detail.Based on equations of uniform transmission line, the formula for calculating compensation degree of controllable shunt reactor which is applicable to various loads of receiving system is achieved by power flow calculation. At the same time, the calculating formula of transmission power is obtained. The relationships of compensation degree, transmission power, voltage and length of the line are studied detailedly. The installation location and capacity of CRT are analyzed, and the installation distance is calculated.On the basis of operational principle of CRT and according to the parameters of the line and flow chart of parameters calculation, the program of M type is compiled, then basic parameters of CRT model are gotten and the model is established. CRT's work mode of sequential single branch is analyzed, and the control system is designed according to its characteristics. At last, the simulation system of UHV AC transmission line with CRT installed in ends is obtained.The operating characteristics of UHV transmission line with CRT installed in ends are analyzed detailedly. Thease include power frequency overvoltage, reactive power, sneaking current and so on. At last, graphical user interface (based on the program files and simulation models) which is used to research the operating characteristics of UHV transmission line with CRT is established and it is used to analyze an example of UHV AC transmission project.