Research On TMR Sensor Based Large Current Measurement Technology

In recent years,the rapid development of smart grids has made the structure of power network more complicated.In order to ensure stable,efficient and safe operation of power system,smart grid puts higher requirements on the accuracy and real-time performance of parameter information(including node current and voltage).Since current is an important parameter in the power system,research on its measurement technology has remained active in modern power system.In order to meet the needs of smart grid development,current measurement method should be high precision,low cost and easy installation.Conventional current transformers suffer from the problem of magnetic saturation due to the usage of a magnetic flux concentrator.Rogowski coil based current transformers that measure current through an integrating circuit can only measure AC power and are not easy to install due to their closed loop configuration.Thanks to its safety,easy installation,small size,low cost,etc.,non-contact current measurement technology based on magnetic sensors has received more and more attention.Among the magnetic sensors,the tunnel magnetoresistance effect based sensor has been under research and applied in the field of current measurement due to its advantages over Hall sensors,giant magnetoresistance effect based sensors and anisotropic magnetoresistance effect based sensors.Since the superposition of the magnetic field and the high sensitivity of the existing magnetic sensor,the magnetic sensor is susceptible to interference from an external magnetic field.Reducing or even eliminating the interference of external magnetic fields is an important issue in the research of magnetic sensor based current measurement technology.Based on the predecessors,this paper has carried out more in-depth research on current measurement technology in smart grid,especially large current measurement technology.The research content mainly deals with the application from the physical level and the algorithm level.Aiming at the application scenarios of gas-insulated substation,busbar and switchgear in power system,after comparing and analyzing the traditional current measurement methods,this paper studies the tunneling magnetoresistance sensor based current measurement method,mainly from the structural design of the sensor placement and the algorithms to eliminate interference.A magnetic sensor array structure is proposed for scenarios where the external disturbance current is parallel to the target current,such as the busbar and the switchgear.Biot-Savar's law and Ampere's circuit Law analyze the magnetic field detected by the magnetic sensor.For the scene where the interference source information is unknown,it is proposed to shield the external complex magnetic field with a high magnetic permeability material.Finally,through simulations and laboratory experiments,the non-contact current technology based on magnetic sensor can make the measurement result have higher precision through effective algorithm and shielding structure,and overcome the shortcomings of the traditional current transformer.