Research Of Dynamic Capacity-increasing For Based On Simultaneous AC-DC Transmission Technology

At the present stage, it is in the industrialization and urbanization process in country,there is a growing demand of electricity power. At the same time, the contradiction between the erection of new transmission lines and the land resource is becoming more and more prominent. The better solution is to transform the existing transmission lines. Don’t change the structure of power grid, it can improve the transmission capacity of existing transmission line.Buried power transmission capacity is excavated, and investment costs is reduced.The scheme of dynamic capacity expansion based on simultaneous AC-DC transmission is designed.The basic principle of simultaneous AC-DC transmission lines is described in detail, and the main circuit topology is analyzed. For the single loop simultaneous AC-DC transmission lines DC power injection device are compared, Zigzag transformer can effectively eliminate the error of current, which caused by DC magnetic bias. Active power, reactive power loss and voltage drop of simultaneous AC-DC transmission lines are analyzed, the results show that reducing the voltage drop along the line and reactive power loss. the construction investment and operation cost can be reduced greatly. The anti-jamming ability can be enhanced by using the fast controllability of HVDC transmission system.The superiority of the dynamic compatibility of simultaneous AC-DC transmission technology is verified.The limiting factors and ways of improving the delivery capacity for simultaneous AC-DC transmission are analyzed in the paper,advantages and disadvantages of several methods about capacity-increasing are analyzed,lead to the AC transmission lines turn into simultaneous AC-DC transmission way,the effect of simultaneous AC-DC transmission is better than AC capacity-increasing is proved by theoretical calculations.Forecasting transport capacity by Elman neural network,A simulation model of simultaneous AC-DC transmission system is constructed.In order to ensure safe operation of the simultaneous AC-DC transmission line after dynamic capacity-increase, using Elman neural network to predict climatic conditions of the transmission line.Calculate the amount of transmission capacity which can increase,provide guidance and reference to the size of inject dc power, and evaluate the safe operation of the transmission after DC power injection. Finally, the correctness andreasonableness of simultaneous AC-DC transmission line theory are verified by the simulation model established in MATLAB software,the results showed that the transmission method can effectively improve the transmission capacity.