阅读说明：本技术 一种基于隧道磁阻传感器的雷电流测量方法 (Lightning current measuring method based on tunnel magnetoresistive sensor ) 是由 向念文 魏定生 赵军 程永健 潘东 汪胜和 檀俊 李科杰 王仕刚 黄杰 杜雨晨 于 2021-06-03 设计创作，主要内容包括：本发明提出了一种基于隧道磁阻传感器的雷电流测量方法,属于电流测量技术领域。该测量方法基于隧道磁阻无芯双轴测量探头,具有结构简单、造价低、体积小、易于安装和维护等优势。该测量方法使用两个隧道磁阻无芯双轴测量探头安装在风力发电机塔筒任意高度的两侧,每个隧道磁阻传感器分别测量所处位置敏感轴方向的磁感应强度,通过测量出的四个磁感应强度和测量点之间的距离,依据本发明提出的测量方法即可反演计算出待测雷电流。本发明的测量方法不受待测导体体积的限制,可应用于任何型号的风力发电机,且不用对传感器的敏感轴方向进行校准,测量结果误差小、可靠度高。(The invention provides a lightning current measuring method based on a tunnel magnetoresistive sensor, and belongs to the technical field of current measurement. The measuring method is based on the tunnel magnetic resistance coreless double-shaft measuring probe and has the advantages of simple structure, low manufacturing cost, small volume, easiness in installation and maintenance and the like. According to the measuring method, two tunnel magnetic resistance coreless double-shaft measuring probes are arranged on two sides of a tower drum of the wind driven generator at any height, each tunnel magnetic resistance sensor is used for measuring the magnetic induction intensity in the direction of a sensitive shaft at the position, and the lightning current to be measured can be calculated in an inversion mode according to the measuring method provided by the invention through the measured four magnetic induction intensities and the distance between measuring points. The measuring method is not limited by the volume of the conductor to be measured, can be applied to wind driven generators of any model, does not need to calibrate the sensitive axis direction of the sensor, and has small error of the measuring result and high reliability.)

1. A lightning current measuring method based on a tunnel magnetoresistive sensor is applied to measuring the lightning current of a wind driven generator when the wind driven generator is struck by lightning, and is characterized by comprising the following steps:

step 1, arranging a measuring device for measuring;

the measuring device comprises two tunnel reluctance coreless double-shaft measuring probes with the same structure, wherein the two probe bodies are respectively marked as a probe T1 and a probe T2; each probe comprises a PCB and two same tunnel magnetoresistive sensors, the PCB in the probe T1 is marked as a board G1, the two tunnel magnetoresistive sensors are respectively marked as a TMR1 sensor and a TMR2 sensor, the PCB in the probe T2 is marked as a board G2, and the two tunnel magnetoresistive sensors are respectively marked as a TMR3 sensor and a TMR4 sensor;

the TMR1 sensor and the TMR2 sensor partition plates are aligned and respectively installed on the front face and the back face of a plate G1 in a back-to-back mode, the TMR3 sensor and the TMR4 sensor partition plates are aligned and respectively installed on the front face and the back face of a plate G2 in a back-to-back mode, the sensing axis of the TMR1 sensor and the sensing axis of the TMR2 sensor are perpendicular to each other, and the sensing axis of the TMR3 sensor and the sensing axis of the TMR4 sensor are perpendicular to each other;

step 2, setting the installation positions of the probe T1 and the probe T2;

recording a tower cylinder of the wind driven generator as a tower cylinder A, recording a cross section at any height of the tower cylinder A as a measuring surface C, and establishing a rectangular coordinate system by taking a central point O of the measuring surface C as a coordinate origin; the probes T1 and T2 are respectively arranged at two sides of the measuring surface C, and the installation position of the probe T1 is simplified to be a first measuring point P₁Simplifying the installation position of the probe T2 to a second measurement point P₂First measurement point P₁And a second measurement point P₂The sensitive axes of the TMR1 sensor and the TMR3 sensor are parallel to the X axis and the directions of the sensitive axes are towards the direction of the negative half shaft of the X axis, the sensitive axes of the TMR2 sensor and the TMR4 sensor are parallel to the Y axis and the directions of the sensitive axes are towards the direction of the positive half shaft of the Y axis,

a first measurement point P₁And a second measurement point P₂The distance is recorded as a distance L, L is more than or equal to 0.5D and less than or equal to 1.2D, and D is the outer diameter of the tower barrel A;

step 3, installing the probe T1 and the probe T2 according to the requirements set in the step 2, and measuring a first measuring point P₁And a measuring point P₂I.e. determining the value of the distance L;

step 4, measuring the magnetic induction intensity of lightning current to the tower drum A through the four tunnel magnetic resistance sensors, and solving to obtain the lightning current I flowing through the tower drum A when the wind driven generator is struck by lightning;

lightning current I flowing through a tower A when the wind driven generator is struck by lightning is measured at a first measurement point P₁The magnetic induction generated is recorded as a first magnetic induction B₁Measuring by using TMR1 sensor to obtain first magnetic induction B₁And is noted as the first horizontal magnetic field value B_1XThe magnetic induction intensity B is measured by a TMR2 sensor₁And is noted as a first vertical magnetic field value B_1Y(ii) a Lightning current I flowing through the tower A when the wind driven generator is struck by lightning is measured at a second measuring point P₂The magnetic induction generated is recorded as a second magnetic induction B₂Measuring with TMR3 sensor to obtain second magnetic induction B₂And is noted as a second horizontal magnetic field value B_2XThe magnetic induction intensity B is measured by a TMR4 sensor₂And is noted as a second perpendicular magnetic field value B_2YCalculating the lightning current I flowing through the tower A when the wind driven generator is struck by lightning according to the following formula:

wherein mu is magnetic permeability in vacuum, and mu is 4 pi multiplied by 10^-7H/m。

Technical Field

The invention relates to the technical field of current measurement, in particular to a lightning current measurement method of a lightning fan based on a tunnel magnetoresistive sensor.

Background

When the wind driven generator is struck by lightning, the lightning current carrying huge energy can generate a transient electromagnetic field in the wind turbine generator, and electromagnetic interference can be generated in an electric power circuit, a signal circuit and an electronic control system to further threaten the safe and stable operation of the wind turbine generator. Accurately measuring lightning current is of great significance to analyzing lightning accidents and improving lightning protection measures.

At present, the existing measuring method has some defects and cannot meet the requirement of accurately and reliably measuring lightning current of a lightning fan. For example, the magnetic tape and magnetic steel bar method can only measure the amplitude and gradient of lightning current and cannot measure the full waveform of the current; the lightning positioning system can only realize large-area lightning information monitoring, the measurement precision is low, and the cost is huge; the Rogowski coil needs 360 degrees to surround the conductor to be measured in the measurement process due to the inherent closed-loop structure, so that the Rogowski coil is not convenient to be used for measuring large structures such as a tower drum of a wind driven generator; the lightning current measurement method based on the optical fiber current sensor has a high measurement bandwidth, but the accuracy is greatly influenced by environmental disturbances such as mechanical vibration and temperature variation. In the document elder, blue epitaxy, wenshushan, bend road, queen feather, xujianwei, weijian, [ J ] instrument technology and sensor, 2017 (10): 46-49), a lightning current measuring system for the whole lightning stroke process of a wind driven generator is designed, which consists of a rogowski coil arranged at a fan carbon brush cabin and a rogowski coil arranged on a tower barrel and is used for measuring the current flowing through the cabin and the current flowing through the tower barrel to ground.

With the continuous development of magnetic sensor technology, non-contact current measurement technology based on magnetic sensors is mature gradually. The non-contact measurement method adopts the magnetic sensor to measure the magnetic field, and then determines the magnitude of the current to be measured according to the relation between the magnetic field and the current, thereby providing a new development direction for the measurement of the lightning current.

Among magnetic sensors, tunnel magnetoresistive sensors offer higher sensitivity, linearity and bandwidth than hall, anisotropic magnetoresistive sensors and giant magnetoresistive sensors, and have the characteristics of good stability, small size, low power consumption, high integration level and wide frequency band. Conventional open or closed loop current sensors based on magnetic sensors require a magnetic core around the conductor to be measured, and such sensors are subject to magnetic saturation, hysteresis, and other magnetic nonlinearities.

In the patent specification of the invention, namely a non-contact current measuring device suitable for a smart grid protection system (CN109444510A), a coreless current measuring method based on a magnetic sensor circular array is provided, a magnetic sensor array is installed on a PCB, and in the coreless method, a plurality of magnetic sensors are installed on a circular ring around a conductor, so that a magnetic core is avoided. However, this circular array method has certain disadvantages that it requires the direction of the sensitive axis of each sensor to be consistent with the direction of the magnetic field generated by the measured current, and assuming that the conductor is located at the center of the sensor array, any deviation in the position offset of the sensing element relative to the conductor and the alignment of the sensitive axis will introduce large errors in the measurement result output.

Based on the method, the applicant considers to design a brand-new measuring method, and then measures the lightning current of the wind driven generator in case of lightning stroke more accurately and conveniently.

Disclosure of Invention

The invention aims to provide a lightning current measuring method based on a tunnel magnetoresistive sensor aiming at the defects of the existing lightning current measuring technology of a lightning fan, so as to solve the problem of system errors caused by the calibration of a sensitive shaft of the sensor during the measurement, and the measurement is not limited by the diameter of a conductor to be measured any more, so that a measuring device is easier to install and maintain, and the convenience and the accuracy of the measurement of the current of a large-diameter conductor (such as the lightning current of a wind driven generator suffering from lightning stroke) are greatly improved.

In order to achieve the purpose, the invention adopts the following technical scheme:

a lightning current measuring method based on a tunnel magnetoresistive sensor is applied to measuring the lightning current of a wind driven generator when the wind driven generator is struck by lightning, and comprises the following steps:

step 1, arranging a measuring device for measuring;

the measuring device comprises two tunnel reluctance coreless double-shaft measuring probes with the same structure, wherein the two probe bodies are respectively marked as a probe T1 and a probe T2; each probe comprises a PCB and two same tunnel magnetoresistive sensors, the PCB in the probe T1 is marked as a board G1, the two tunnel magnetoresistive sensors are respectively marked as a TMR1 sensor and a TMR2 sensor, the PCB in the probe T2 is marked as a board G2, and the two tunnel magnetoresistive sensors are respectively marked as a TMR3 sensor and a TMR4 sensor;

the TMR1 sensor and the TMR2 sensor partition plates are aligned and respectively installed on the front face and the back face of a plate G1 in a back-to-back mode, the TMR3 sensor and the TMR4 sensor partition plates are aligned and respectively installed on the front face and the back face of a plate G2 in a back-to-back mode, the sensing axis of the TMR1 sensor and the sensing axis of the TMR2 sensor are perpendicular to each other, and the sensing axis of the TMR3 sensor and the sensing axis of the TMR4 sensor are perpendicular to each other;

step 2, setting the installation positions of the probe T1 and the probe T2;

recording a tower cylinder of the wind driven generator as a tower cylinder A, recording a cross section at any height of the tower cylinder A as a measuring surface C, and establishing a rectangular coordinate system by taking a central point 0 of the measuring surface C as a coordinate origin; the probes T1 and T2 are respectively arranged at two sides of the measuring surface C, and the installation position of the probe T1 is simplified to be a first measuring point P₁The installation position of the probe T2 is simplified to the fourthTwo measurement points P₂First measurement point P₁And a second measurement point P₂The sensitive axes of the TMR1 sensor and the TMR3 sensor are parallel to the X axis and the directions of the sensitive axes are towards the direction of the negative half shaft of the X axis, the sensitive axes of the TMR2 sensor and the TMR4 sensor are parallel to the Y axis and the directions of the sensitive axes are towards the direction of the positive half shaft of the Y axis,

a first measurement point P₁And a second measurement point P₂The distance is recorded as a distance L, L is more than or equal to 0.5D and less than or equal to 1.2D, and D is the outer diameter of the tower barrel A;

step 3, installing the probe T1 and the probe T2 according to the requirements set in the step 2, and measuring a first measuring point P₁And a measuring point P₂I.e. determining the value of the distance L;

step 4, measuring the magnetic induction intensity of lightning current to the tower drum A through the four tunnel magnetic resistance sensors, and solving to obtain the lightning current I flowing through the tower drum A when the wind driven generator is struck by lightning;

lightning current I flowing through a tower A when the wind driven generator is struck by lightning is measured at a first measurement point P₁The magnetic induction generated is recorded as a first magnetic induction B₁Measuring by using TMR1 sensor to obtain first magnetic induction B₁And is noted as the first horizontal magnetic field value B_1XThe magnetic induction intensity B is measured by a TMR2 sensor₁And is noted as a first vertical magnetic field value B_1Y(ii) a Lightning current I flowing through the tower A when the wind driven generator is struck by lightning is measured at a second measuring point P₂The magnetic induction generated is recorded as a second magnetic induction B₂Measuring with TMR3 sensor to obtain second magnetic induction B₂And is noted as a second horizontal magnetic field value B_2XThe magnetic induction intensity B is measured by a TMR4 sensor₂And is noted as a second perpendicular magnetic field value B_2YCalculating the lightning current I flowing through the tower A when the wind driven generator is struck by lightning according to the following formula:

wherein mu is magnetic permeability in vacuum, and mu is 4 pi multiplied by 10^-7H/m。

Compared with the prior art, the measuring method has the following beneficial effects:

1. according to the lightning current measuring method based on the tunnel magnetoresistive sensor, the solution of the measured current is irrelevant to the relative distance and displacement between the sensor and the conductor, and is only relevant to the distance between two probes of the tunnel magnetoresistive coreless sensor and different magnetic field components. The method does not need to carry out relative calibration on the sensitive shaft of the sensor in the measuring process, is easy to install and maintain, and is convenient and reliable.

2. The measuring device does not need to surround the measuring probe on the conductor to be measured in the measuring process, is not limited by the size of the tower of the wind driven generator in the actual installation and application process, can be applied to wind driven generators of any type, is easy to popularize and reduces the measuring cost.

3. The tunnel magnetic resistance coreless double-shaft measuring probe adopted by the invention has the advantages of small volume, high precision and large lightning current measuring range, and can meet the lightning current measuring requirement when the wind driven generator is struck by lightning.

Drawings

FIG. 1 is a schematic diagram of the operation of the measurement method of the present invention.

FIG. 2 is a schematic view of the mounting positions of probe T1 and probe T2 on a tower.

Fig. 3 is a schematic view showing the mounting positions of the probe T1 and the probe T2 on the measurement plane C.

FIG. 4 is a diagram illustrating relative positions of a current source and a tunnel magnetoresistive sensor in a numerical simulation.

Fig. 5 is a schematic diagram illustrating the influence of the change of the relative position of the current source on the measurement error in the numerical simulation.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

In this embodiment, the current measuring method of the present invention is described by taking the measurement of the transient lightning current of the wind turbine when the wind turbine is struck by lightning as an example.

Fig. 1 is a schematic view of the operation of the measuring method of the present invention, fig. 2 is a schematic view of the installation positions of the probe T1 and the probe T2 on the tower, and fig. 3 is a schematic view of the installation positions of the probe T1 and the probe T2 on the measuring plane C. In fig. 2 and 3, the structures of two PCB boards and four identical tunnel magnetoresistive sensors are enlarged. As can be seen from fig. 1 to 3, the method for measuring lightning current based on a tunnel magnetoresistive sensor of the present invention is applied to measuring lightning current of a wind turbine generator in case of lightning stroke, and comprises the following steps:

step 1, a measuring device is arranged for measuring.

The measuring device comprises two tunnel reluctance coreless double-shaft measuring probes with the same structure, wherein the two probe bodies are respectively marked as a probe T1 and a probe T2; each probe comprises a PCB board and two identical tunnel magnetoresistive sensors, the PCB board in the probe T1 is denoted as board G1, the two tunnel magnetoresistive sensors are denoted as a TMR1 sensor and a TMR2 sensor, respectively, the PCB board in the probe T2 is denoted as board G2, and the two tunnel magnetoresistive sensors are denoted as a TMR3 sensor and a TMR4 sensor, respectively.

The TMR1 sensor and the TMR2 sensor partition plates are aligned and respectively installed on the front face and the back face of a plate G1 in a back-to-back mode, the TMR3 sensor and the TMR4 sensor partition plates are aligned and respectively installed on the front face and the back face of a plate G2 in a back-to-back mode, the sensitive shaft of the TMR1 sensor and the sensitive shaft of the TMR2 sensor are perpendicular to each other, and the sensitive shaft of the TMR3 sensor and the sensitive shaft of the TMR4 sensor are perpendicular to each other.

As can be seen from fig. 2, two tunnel magnetoresistive sensors are arranged back-to-back on each PCB.

And 2, setting the installation positions of the probe T1 and the probe T2.

Recording a tower cylinder of the wind driven generator as a tower cylinder A, recording a cross section at any height of the tower cylinder A as a measuring surface C, and establishing a rectangular coordinate system by taking a central point O of the measuring surface C as a coordinate origin; the probes T1 and T2 are respectively arranged at two sides of the measuring surface C, and the installation position of the probe T1 is simplified to be a first measuring point P₁Simplifying the installation position of the probe T2 to a second measurement point P₂First measurement point P₁And a second measurement point P₂Is parallel to the X-axisIn the row, the sensitive axes of the TMR1 sensor and the TMR3 sensor are parallel to the X axis and are all oriented towards the direction of the negative half axis of the X axis, and the sensitive axes of the TMR2 sensor and the TMR4 sensor are parallel to the Y axis and are all oriented towards the direction of the positive half axis of the Y axis.

A first measurement point P₁And a second measurement point P₂The distance is recorded as distance L, L is more than or equal to 0.5D and less than or equal to 1.2D, and D is the outer diameter of the tower barrel A.

In this embodiment, a height is arbitrarily selected on the tower a, a cross section is made to be a measurement surface C, and the two probes are respectively installed on two sides of the measurement surface C, that is, only the two probes are required to be installed at the same horizontal height of the tower a.

Step 3, installing the probe T1 and the probe T2 according to the requirements set in the step 2, and measuring a first measuring point P₁And a measuring point P₂I.e. the value of the determined distance L.

In this embodiment, L is 1.2D.

And 4, measuring the magnetic induction intensity of the lightning current to the tower cylinder A through the four tunnel magnetic resistance sensors, and solving to obtain the lightning current I flowing through the tower cylinder A when the wind driven generator is struck by lightning.

Lightning current I flowing through a tower A when the wind driven generator is struck by lightning is measured at a first measurement point P₁The magnetic induction generated is recorded as a first magnetic induction B₁Measuring by using TMR1 sensor to obtain first magnetic induction B₁And is noted as the first horizontal magnetic field value B_1XThe magnetic induction intensity B is measured by a TMR2 sensor₁And is noted as a first vertical magnetic field value B_1Y(ii) a Lightning current I flowing through the tower A when the wind driven generator is struck by lightning is measured at a second measuring point P₂The magnetic induction generated is recorded as a second magnetic induction B₂Measuring with TMR3 sensor to obtain second magnetic induction B₂And is noted as a second horizontal magnetic field value B_2XThe magnetic induction intensity B is measured by a TMR4 sensor₂And is noted as a second perpendicular magnetic field value B_2YCalculating the lightning current I flowing through the tower A when the wind driven generator is struck by lightning according to the following formula:

wherein mu is magnetic permeability in vacuum, and mu is 4 pi multiplied by 10^-7H/m。

In order to verify the feasibility of the measuring method, the method is subjected to simulation verification.

FIG. 4 is a diagram illustrating relative positions of a current source and a tunnel magnetoresistive sensor in a numerical simulation. The black dots in the figure represent the current source. And carrying out numerical simulation by using MATLAB to calculate the measuring method. And establishing a rectangular coordinate system, fixing the positions of the four tunnel magnetoresistive sensors during calculation, keeping the positions of the four tunnel magnetoresistive sensors unchanged at (-2m, 0) and (0, 2m), adopting constant current as a current source, and performing scanning movement in a rectangular area of (-2m, + 2m), which is equivalent to simulating the movement of two tunnel magnetoresistive coreless double-axis measuring probes in the area, thereby simulating the deviation of an actual installation position.

When the constant current source is positioned at different positions, the magnetic field sizes at the two positions are obtained through numerical calculation, inversion calculation is carried out by using the measuring method of the invention to obtain a current measured value, and then the absolute error between the current measured value and the actual current value of the current source is calculated. The effect of the current source relative position change on the current measurement Error result is shown in fig. 5, and it can be seen from the figure that the current measurement method can theoretically realize a very small current measurement Error under any different relative positions, and the maximum Value of the absolute Error Value is 6 × 10^-16. Therefore, even if a certain installation position offset exists between the probe and the tower drum, the current measurement by adopting the measurement method provided by the invention can also ensure higher measurement precision.

Establishing lightning stroke transient state of the wind driven generator in a CST microwave working chamber, carrying out simulation calculation, and injecting 8/20 mus standard lightning current with the amplitude of 100kA to the top end of the blade at the highest position of the wind driven generator. The difference and the ratio of the current amplitude and the source current amplitude of each position at different lightning stroke points at 10 mu s are obtained according to the simulation result and are shown in table 1:

from the quantitative analysis in table 1, it can be seen that when the current leaks to the tower, there is a slight attenuation of the current amplitude due to the loss and shunt, which is about 1%. The current attenuation amplitude of the upper section, the middle section and the lower section of the tower cylinder is relatively smaller, the current attenuation amplitude of the tower cylinder is at most 0.4%, and the current amplitude of the tower cylinder section accounts for about 98.5% of the total current.

On the basis of analyzing the lightning transient electromagnetic characteristics of the wind driven generator, the feasibility of the provided lightning current measuring method of the lightning wind driven generator is verified.

The method ensures that the lightning stroke condition (set to strike the top end of the blade at the highest position of the wind driven generator) is unchanged, 8/20 mus standard lightning current waveform with the amplitude of 100kA is applied to the top end of the blade at the highest position of the wind driven generator, a magnetic field probe is arranged at any relative position near different heights of a tower barrel according to the placement position of a tunnel magnetoresistive sensor in the measuring method, the measuring method is utilized to calculate the current obtained when the sensor is arranged at different height positions, and the current is compared with the actual lightning current monitored by a current monitor at the position, and the relative error of the amplitude is shown in a table 2:

as can be seen from Table 2, except that the error of the inversion current is large at two positions close to the bottom end and the top end of the tower, an accurate result can be obtained at any position between 3m and 73m of the tower, wherein the minimum error is only 0.29%, so that the selection range of the measurement surface C is wide, and the adaptability is strong.