Study On Light-weight Induction Power Supply For On-line Monitoring Equipment Of Distribution Network Line

With the rapid development of China’s electric power industry,the power grid not only covers the whole country more and more densely,but also develops in the direction of more and more automation and intelligence.Online monitoring technology has become an important part of the development of strong smart grid in China.However,due to the complexity of the working environment,the power supply problem for the on-line monitoring equipment has become one of the important constraints for the development of this technology.Hence using energy collection technology to convert the energy from nature and around transmission lines into usable electric energy has gradually become a solution to the problem.With the development of microelectronic technology,ultra-low power devices and wireless communication modules provide an excellent application platform for the development of online energy harvesting technology on distribution lines.In this paper,a corresponding online energy harvesting power supply is designed for the online monitoring equipment of the transmission line of the distribution network.The magnetic field energy around the transmission line is induced by using energy harvesting CT,which is converted into electrical energy,and then transformed by circuit to provide stable and reliable low-voltage direct current.Then use with solar energy as auxiliary,and equipped with lithium battery as energy storage backup to constitute the overall power supply.The principle and output characteristics of magnetic induction energy extraction are theoretically analyzed,the advantages and limitations of the current energy extraction method are analyzed,and the measures to delay core saturation are explored.Then,the methods to suppress core saturation are discussed from core material,size parameters and air gap.The power characteristics of magnetic induction energy extraction coil under ideal linear condition and practical working condition are analyzed theoretically,and the output power is approximately proportional to the square of primary current.The relationship between power density and inner and outer diameter of magnetic core under ideal conditions and between output power and filter capacitance in practical application is analyzed.It is found that there exists a maximum output power point,and the number of turns in the secondary winding does not affect the maximum output power.Furthermore,the structure and size of the CT energy fetching end are optimized.Firstly,NSGA-II algorithm was used to optimize the size of the magnetic core at the energy harvesting end of CT,and its volume was minimized to make it light while ensuring the output power.At the same time,the magnetic core structure is optimized,and the magnetic core with internal and external double ring structure is designed.The parallel magnetic circuit is formed locally in the magnetic core,and the magnetic leakage of the magnetic core is reduced.After simulation analysis and comparison,the effectiveness of the optimization is verified.After optimized design,the magnetic core not only greatly improves the energy fetching power of the CT energy fetching end,but also greatly reduces the weight,which alleviates the load bearing burden of the transmission line,and solves the existing problems of the energy fetching method to a certain extent.The hardware circuit of the corresponding power conversion is designed,and the hybrid access of magnetic field and solar energy is realized through the energy management chip.In addition,the lithium battery is equipped as the backup of energy storage.When the output power of the energy harvesting end is enough,the lithium battery can be charged and power to the load at the same time.When the output power of the power fetching end is not large enough,it supplies power only to the load.When the output power of the energy harvesting end is very small,the lithium battery supplies power to the load.The overall power supply strategy greatly enhances the stability and reliability of the power supply,and improves the shortcomings of insufficient output power and unstable output of the single energy harvesting power supply on the current transmission line,which has a certain engineering practical significance.Finally,an experimental platform was built to simulate the power supply,and the overall weight of the power supply was 1.47 kg.In the laboratory environment,in the simulation of 10-900 A primary wire current,the power supply is successfully run,and the load is stable and reliable power supply,which verifies the feasibility of the design to a certain extent.