Study On Coreless TMR Array Current Measurement Method Considering External Magnetic Field

Accurate current measurements is of great significance to the safe operation of the power grid.The array type coreless current sensor has good linearity dynamic range the advantages of small volume weight compared with iron core current sensor,and is widely followed.Howerver the coreless fails to shield the external magnetic field,influencing the accuracy of current measurement of the sensor array.In addition,the current measurement error of the model caused by the wire bending decreases the current measurement accuracy as well.Thus,this paper focuse on the study on coreless TMR array current measurement method considering external magnetic field and the wire bending.This paper selected three shaft tunneling Magnetoresistance chip as the magnetic component,and established the magnetic field calculation model considering external magnetic field and the wire bending.The simulation analyes the current measurement error considering the above two factors,and put forward the corresponding improved algorithm,and finally verified the effeciency through the experiment.The main achievements of this paper are as follows.(1)The paper analyses the performance of the three long straight wire current measurement method(the non-positioning algorithm,the 2D-positioning algorithm and the 3D-positioning algorithm),and the influence of relevant parameters on the current measurement errors of the above three algorithms is simulated theoretically,and the results show that the influence of the external magnetic field on the current measurement of the long straight conductor is not negligible,especially the influence of the inclination Angle and distance of the current carrying conductor.(2)This paper presents a current measurement method considing the external magnetic field,and analyzes the variation of the current measurement error of the improved method when the relevant parameters change.The simulation results show that the proposed method can accurately measure the current value of the target conducter,and the absolute value of error is within 2% when 40 d B noise is added.In addition,this method can also be used for ac current measurement.Compared with the non-positioning algorithm and the positioning algorithm,the accuracy of current measurement has been greatly improved.(3)The experimental verification of the improved method is carried out,and the current measurement system based on three-axis TMR array was designed.Including three-axis TMR element selection,open-type PCB design and experimental system construction.The non-positioning algorithm,three-dimensional wire positioning algorithm and the improved method were verified experimentally.The experiment shows that the improved method can greatly reduce the measurement error,which can be as low as 3%.(4)The calculation model of magnetic induction strength of bent conductor is established,the calculation value of current and its error based on ampere loop theorem are analyzed,the influence of various parameters on the error is discussed,and the improved method of current measurement of bent conductor is put forward.The simulation results show that the measured current value can be accurately obtained without adding noise.The absolute value of error is within 1.5% when 40 d B noise is added.Meanwhile,this method can be applied to ac current measurement.