Research And Design Of Energy-Taking Current Transformer Device

As the main artery of the whole power system,the safe,stable and reliable operation of high voltage transmission lines is very important.To achieve this purpose,more and more online monitoring devices have been put into use.High voltage transmission lines are located in harsh field environment and wide distribution area,so the existing energy acquisition methods cannot meet the requirements of online monitoring equipment operation.In thesis,after deeply understanding the difficulties of online monitoring devices taking up energy and analyzing the working mechanism of Current Transformer(CT)in detail,a CT energy-taking device is studied and designed.Firstly,Ansys software was used to carry out simulation analysis and verification from the aspects of core material,core air gap structure and selection of secondary side turns,mainly through the analysis of B-H curve under different materials,core saturation under different air gap structure,CT output power changes with the number of secondary side turns,and according to the simulation results to complete the optimization design of the core.This not only effectively reduces the starting current,but also increases the upper limit of current adaptation of the transmission line,which lays a foundation for the subsequent circuit design.Secondly,aiming at the problem of wide range of line current fluctuation caused by unstable power load,the analysis is mainly carried out from the following perspectives: When the primary side current is small,the output characteristics of CT energy-taking and the cooperative power supply mode of auxiliary battery are analyzed respectively.It is concluded that the parallel matching capacitor on the secondary side and the cooperative power supply mode of auxiliary battery can effectively improve the output power of CT energy-taking and prolong the battery life of CT energy-taking device.When the primary side current is large,a semi-active rectifier voltage regulator method is proposed by comparing and analyzing the working process of passive rectifier,semi-active rectifier and full active rectifier,and is verified by Matlab/Simulink simulation.It is concluded that this method can effectively solve the energy overflow problem when the primary side current is too large and improve the heating condition of the energy taking device.At the same time,a PWM control method based on Buck type DC-DC circuit is proposed to ensure the stable and reliable work of the load.Finally,the CT energy-taking device is designed according to the above theoretical simulation results.The experimental platform was built to simulate the actual working condition of the transmission line,and a number of tests were carried out on the device.The test results show that the CT energy-taking device can stably reach 7W output in the line current range of 20～1200A,and there is no significant heating at high current,basically achieving the objective of thesis,and further verifying the effectiveness of the research and design in thesis.