Research And Design Based On Impedance Matching For Transmission Line Online Energy Acquisition Method

With the development of smart grid in China,the construction of UHV transmission and EHV transmission engineering,it is very important to monitor the real-time state of the transmission lines to ensure the safe operation of the transmission lines.However,the power supply problem of the transmission line monitoring equipment has been the key factor restricting its development and application.In several power supply sources of the monitoring equipment,the online energy source based on the open magnetic core has good practical application value.This thesis aims at the shortcomings of large starting current and small output power for conventional current transformers inductive energy acquisition method based on open magnetic core,and an on-line energy harvesting method for transmission lines based on impedance matching be proposed.In this method,parallel resonance is generated by matching the series capacitance of the secondary wingding of the open air gap magnetic core with its excitation inductor,thereby increasing the equivalent impedance of the damping branch where the magnetic core is located,the load can get more current and electric energy through the other branch.In this thesis,firstly according to the principle of on-line energy acquisition on transmission line based on impedance matching,the equivalent circuit model of the damping branch in on-line energy acquisition method is established,the relationship between output power of on-line energy acquisition method and the parameters of damping branch core is quantitatively analyzed and calculated,so that the optimized design of the damping branch magnetic core is carried out.Secondly,in order to achieve maximum power output in a given load condition,the PWM rectifier circuit based on input impedance control is adopted.The rectifier circuit can regulate its input impedance,and then achieve maximum power output and control the current of the bus current to the energy fetching branch,ensure power supply can work normally under a wide range of bus current.At the same time,the hardware circuit design of online energy acquisition power supply system is also carried out.Finally,the correctness and effectiveness of the theoretical analysis are verified by MATLAB Simulink software simulation and system experiment.The results show that the on-line energy acquisition method based on impedance matching can obtain more power than conventional current transformer induction energy acquisition method under the same condition.And the on-line power supply system designed by this method can output a stable 12V voltage under a wide range of bus current and provide a power of not less than 10W when the bus current is 50A,the on-line power supply system is satisfied with the voltage and power requirements of subsequent monitoring equipment.