Research On Inductive Energy Extraction Under Ground Resonant Compensation Of Overhead Transmission Lines

With the rapid development of smart grids,online monitoring terminals are increasingly widely used in power grids,and the key factor affecting their application is the power supply problem of online monitoring terminals.Currently,the online monitoring terminal power supply method usually selects a combination of solar panels and batteries,which is susceptible to climate and environmental factors and has a short service life cycle;If traditional current transformer ground wire energy extraction methods are used,problems such as insufficient power in the energy extraction system and saturation of the magnetic core will result,greatly reducing the power supply reliability of the online monitoring terminal.Aiming at the problems existing in the above power supply methods,this paper proposes a multi-stage transformer group energy extraction method with overhead ground wire resonance compensation.Firstly,based on the basic principle of inductive energy extraction of overhead ground wire,this paper compares the advantages and disadvantages of the energy taking methods of single and two overhead ground wires,and the design of the energy harvesting system is carried out on two overhead ground wires that are grounded tower by tower by optical cable ground wire and single point by common ground wire,the spatial geometric distribution of the overhead line and the influence of the line parameters on the input parameters of the system under this grounding mode are analyzed,and the input parameters of the energy taking system are adjusted.Then,based on the equivalent parameters of the ground wire,a multi-stage energy-taking transformer group with resonance compensation is designed.The energy-taking transformer group consists of tuning,energy-taking and energy-collecting circuits.The tuning circuit is used to compensate the reactive power loss of the external input of the system,while the internal reactive power of the system is compensated by the resonant capacitance of the energy-taking and energy-collecting circuits.Then the equivalent circuit model of the energy transformer group is established,the current expression of each circuit is solved,and the output power function is derived.Taking the key parameters in the function as the target,the functional relationship between the physical parameters and the electrical parameters of the energy transformer group is established,and the influence of the physical parameters on the system output power is derived.At the same time,using Maxwell and Simulink to conduct simulation analysis on the energy harvesting system,the results show that the current and voltage phases of each circuit in the energy extraction system designed in this paper are consistent,the reactive power loss in the system is compensated,and the output power is greatly improved compared with the conventional single-stage transformer energy extraction system.At last,an experimental prototype and related test platform of resonant compensation for multi-stage transformer group ground wire are built.The experimental results are basically consistent with the simulation analysis.When the system input is the average current of the ground wire 8A,the output power of the system can reach 5.16 W,which is more than 6 times of the output power of the conventional single-stage transformer energy extraction system,which greatly improves the output power of the system.At the same time,when the ground wire current reaches the maximum value of15 A,the magnetic core is not saturated,which ensures that the energy extraction system can pick up electric energy on the ground wire for a long time,and improves the reliability of the online monitoring terminal power supply.