Research On Constant Current And Constant Voltage Inductive Power Transfer System Based On Domino-Coil Structure

With the development of smart power grid,Online Monitoring Equipment(OME)plays an increasingly important role in it,and how to supply power safely and stably for OME is a difficulty.Solar and wind power are too influenced by the environment to supply a steady power.And battery power supply directly requires frequent battery replacement is not a good choice considering the safety cost and labor cost.The current more popular power supply mode is: Energy in the magnetic field of the transmission line is captured through a Current Transformer(CT)mounted on the transmission line.Then the technology of Inductive Power Transfer(IPT)is adopted.The energy is transmitted to the storage battery in the OME level by level through a domino coil spaced relay coil concentrically.The advantages of this CT charging + domino coil structure are stable energy supply and high safety.In the current studies that use domino coil structure and IPT technology to charge OME,most of them only realize Constant Voltage(CV)charge or Constant Current(CC)charge.However,in order to give consideration to charging safety and speed,the usual charging method is CC/CV charging: use CC charging first,and then switch to CV charging when the voltage rises to a certain value.At present,CC/CV charging can be realized by frequency control,phase shift control or adding front and rear DC-DC converter to control the output voltage and current,so as to achieve CC/CV output.However,the control algorithm of this method is too complex and will lead to the increase of system volume.CC/CV charging through hybrid topology + on and off of additional switches simplifies the control algorithm,but the system complexity is still high due to the introduction of additional components.To solve the above problems,this paper proposes a CC/CV output method that switches the system working frequency once only without complex control and additional components.Firstly,deduce and establish the theoretical model of constant current and constant voltage output of IPT system containing N coils based on matrix theory.Secondly starting from a specific five-coil IPT system,analyze the characteristics of IPT system based on domino coil structure in detail,including frequency characteristics,parameter sensitivity and efficiency characteristics.Then,based on the theoretical model and considering the efficiency and output stability,a parameter design process is proposed for the IPT system with any number of coils and configurable output gain.Finally,A five-coil IPT system prototype with input voltage of 20 V,constant current charging current of 1 A and constant voltage charging voltage of 18 V was built.In the CC charging process,the load current only fluctuates 2%,and the maximum efficiency is 61.7% with stable current.In the process of CV charging,the load voltage fluctuates only 6.1%,and the maximum efficiency is 64%.At the moment of load switching,current fluctuation is 1%,voltage fluctuation is 1.3%;During the whole charging process,the reactive power can be ignored.This verifies the correctness of the theoretical model and parameter design process and the feasibility of realizing constant current/constant voltage charging method by switching frequency.