阅读说明：本技术 一种基于tmr的无接触式绞线电流检测方法 (TMR-based contactless stranded wire current detection method ) 是由 贾俊 于 2021-09-28 设计创作，主要内容包括：本发明涉及电流检测领域,具体公开一种基于TMR的无接触式绞线电流检测方法,利用高性能的TMR磁阻元件获取绞线外三个点的磁场信号,经解析模型计算后获取绞线内的三相电流值。本发明对于TMR磁阻元件的安装位置没有特殊要求,安装精度的误差可通过解算的关系矩阵进行有效的补偿,降低了对安装精度的要求。同时,由于不需要与绞线产生电气连接,可以有效地降低电流传感器的安装费用与维护费用。(The invention relates to the field of current detection, and particularly discloses a TMR-based non-contact stranded wire current detection method. The invention has no special requirement on the installation position of the TMR magnetoresistive element, and the error of the installation precision can be effectively compensated through the solved relation matrix, thereby reducing the requirement on the installation precision. Meanwhile, because the current sensor does not need to be electrically connected with a stranded wire, the installation cost and the maintenance cost of the current sensor can be effectively reduced.)

1.A TMR-based contactless stranded wire current detection method is characterized in that: the three-phase current-limiting TMR circuit comprises a plurality of TMR magnetoresistive elements, and the output signals of the TMR magnetoresistive elements are calculated by a resolving circuit to obtain a three-phase current value.

2. The TMR-based contactless stranded-wire current detection method according to claim 1, characterized in that: the TMR magnetoresistive element is provided in 3.

3. The TMR-based contactless stranded-wire current detection method according to claim 2, characterized in that: the solution circuit uses a non-singular matrix with a matrix of 3 x 3.

4. The TMR-based contactless stranded-wire current detection method according to claim 2, characterized in that: the three TMR magnetoresistive elements can be distributed at any point outside the stranded wire.

5. A TMR-based contactless stranded wire current detection method is characterized by comprising a plurality of TMR magnetoresistive elements arranged outside a stranded wire, and the method comprises the following steps:

1) after the installation is finished, three-phase symmetrical current flows in the stranded wire, voltage signals of a plurality of TMR magnetoresistive elements are obtained, the analytical relation between the voltage signals and the three-phase symmetrical current is established, and a non-singular relation matrix is formed;

2) voltage signals from the TMR magnetoresistive elements pass through a scaling circuit, so that the value of an analog signal is within the voltage sampling range of a digital signal processor, and the value of the analog signal is converted into a digital signal value through a digital sampling circuit;

3) the result of the inversion of the nonsingular relation matrix is an inverse-deducing nonsingular matrix which takes the voltage signals output by the TMR magnetoresistive elements as input variables and three-phase currents in the stranded wire as output variables;

4) and multiplying the digital signal value as an input variable by the inverse-recursive nonsingular matrix to obtain a preliminary three-phase current value. And (5) carrying out equal-proportion amplification on the primary three-phase current value to obtain the actual current value. Wherein the amplification ratio and the voltage signal reduction ratio of the TMR magnetoresistive elements are inverse numbers.

6. The TMR-based contactless stranded-wire current detection method according to claim 5, wherein the non-singular relationship matrix in step 1) is determined after the installation position is confirmed and before the cable is put into actual operation.

7. The TMR-based contactless stranded-wire current detection method according to claim 5, wherein the TMR magnetoresistive element is provided in 3.

8. The TMR-based contactless stranded-wire current detection method according to claim 7, wherein the non-singular relation matrix in the step 1) is a 3 x 3 non-singular matrix.

Technical Field

The invention relates to the field of current detection, in particular to a TMR-based contactless stranded wire current detection method.

Background

The contactless current sensor is an interface device between high and low voltages that detects a current value by using a magnetic field generated by a current in an electrically insulated state. The magnetic sensor is a key device in the magnetic sensor and plays an important role in the performance of the sensor. Current sensor in the existing market mainly adopts traditional Hall device, and because semiconductor material self reason, Hall device's temperature drift volume is great, and the uniformity is poor, and especially in the low temperature region change acutely, be difficult to carry out unified calibration. The use of dynamic offset cancellation techniques may partially improve the hall device. The tunnel magneto-resistance (TMR) device is a new generation of magneto-sensitive device following a Hall device, an anisotropic magneto-resistance AMR and a giant magneto-resistance GMR, and has the characteristics of low power consumption, low temperature drift and high sensitivity. In the current sensor, the sensitivity and the temperature characteristic of the current sensor can be remarkably improved by adopting TMR instead of a Hall device.

One type of the existing power grid current detection device is a contact type current sensor, namely, the sensor is connected with a primary side or a secondary side of a transformer in series for current detection. For example, chinese patent publication No. CN107907715A discloses a "connecting device for a transformer and a current sensor", which provides a connecting structure between a transformer and a current sensor, wherein the transformer and the current sensor are connected into a whole by detachably connecting an adapter plate and a current sensor fixing plate. This approach increases installation costs as well as maintenance costs.

Conventional contactless current sensors are usually designed as a clamp structure. The current conductor of the circuit to be tested passing through the iron core becomes the primary coil of the current transformer, wherein the current is induced in the secondary coil by the current, thus realizing the non-contact current detection. For example, chinese patent publication No. CN103956878A discloses a "current sensor testing apparatus and testing method", in which a current clamp with known accuracy and a current clamp with unknown accuracy are simultaneously placed on a wire to perform an accuracy test of a current sensor. However, the three-phase current is in the stranded wire, and the sum of the three-phase current is zero, so that the traditional current clamp cannot meet the current detection of the stranded wire.

Disclosure of Invention

The TMR-based contactless stranded wire current detection method is high in current detection precision and low in installation and maintenance cost.

In order to solve the technical problem, the present application provides the following technical solutions:

a TMR-based contactless stranded wire current detection method comprises a plurality of TMR magneto-resistive elements, wherein output signals of the TMR magneto-resistive elements are calculated through a resolving circuit to obtain a three-phase current value.

Further, the TMR magnetoresistive element is provided in 3.

Further, the solving circuit utilizes a non-singular matrix with a matrix of 3 x 3.

Further, the three TMR magnetoresistive elements may be distributed at any point outside the strand.

The invention adopts a technical scheme of a non-contact stranded wire current detection method, and adopts a TMR magneto-resistive element with high performance. Three magnetic field detection points are determined outside the stranded wire. According to the superposition theorem, the magnetic field signal at a certain point outside the stranded wire is obtained by linearly superposing magnetic field lines generated by three-phase currents respectively. And (3) forming a non-singular matrix of 3 x 3 by establishing a relation between magnetic field values at three magnetic field detection points and three-phase currents. When the magnetic fields at the three points are known, the inverse matrix of the nonsingular matrix is used for calculating the three-phase current value in a reversible way.

A TMR-based contactless stranded wire current detection method comprises a plurality of TMR magneto-resistive elements arranged outside a stranded wire, and comprises the following steps:

1) after the installation is finished, three-phase symmetrical current flows in the stranded wire, voltage signals of a plurality of TMR magnetoresistive elements are obtained, the analytical relation between the voltage signals and the three-phase symmetrical current is established, and a non-singular relation matrix is formed;

2) voltage signals from the TMR magnetoresistive elements pass through a scaling circuit, so that the value of an analog signal is within the voltage sampling range of a digital signal processor, and the value of the analog signal is converted into a digital signal value through a digital sampling circuit;

3) the result of the inversion of the nonsingular relation matrix is an inverse-deducing nonsingular matrix which takes the voltage signals output by the TMR magnetoresistive elements as input variables and three-phase currents in the stranded wire as output variables;

4) and multiplying the digital signal value as an input variable by the inverse-recursive nonsingular matrix to obtain a preliminary three-phase current value. And (5) carrying out equal-proportion amplification on the primary three-phase current value to obtain the actual current value. Wherein the amplification ratio and the voltage signal reduction ratio of the TMR magnetoresistive elements are inverse numbers.

Further, the non-singular relation matrix in the step 1) is determined before the cable is put into actual operation after the installation position is confirmed.

Further, the TMR magnetoresistive element is provided in 3.

Further, the non-singular relation matrix in the step 1) is a non-singular matrix of 3 × 3.

The working process is as follows: a TMR-based contactless stranded wire current detection method comprises three TMR magnetoresistive elements arranged outside a stranded wire and a matched calculating circuit, and comprises the following steps:

1) processing the voltage signal output by TMR, and reducing the voltage signal by equal proportion to meet the requirement of the signal voltage range of the digital signal processor;

2) processing the analog signal into a digital signal to be processed by utilizing AD sampling;

3) according to the inverse matrix of the set nonsingular matrix, performing reverse-derivation calculation to obtain a digital signal of the three-phase current value;

4) the digital signal of the three-phase current value is amplified in equal proportion to obtain an actual current value, and the proportion of the actual current value and the proportion in the step 1) are reciprocal;

the TMR magneto-resistive elements are arranged at different three angles outside the stranded wire, and the distances from the centers of the stranded wires are the same.

Has the advantages that: the invention utilizes the non-contact current detection device of the TMR magnetoresistive element to detect the three-phase current in the stranded wire, thereby reducing the installation and maintenance cost of the current sensor.

Drawings

FIG. 1 is a schematic view of assembling a TMR magnetoresistive element according to the present invention;

fig. 2 is a solving flow chart.

Detailed Description

The following is further detailed by way of specific embodiments:

the reference numbers in the drawings of the specification include: the phase-A lead wire, the phase-B lead wire, the phase-C lead wire, the stranded wire, the first TMR magneto-resistive element, the second TMR magneto-resistive element, and the third TMR magneto-resistive element are respectively 1, 2, B, 3, C, 4, 5, 6, 7.

As shown in fig. 1-2, a non-contact stranded wire current detection method based on TMR includes a non-contact current detection device, the non-contact current detection device includes a plurality of TMR magnetoresistive elements, in the present invention, three TMR magnetoresistive elements are adopted, which are a first TMR magnetoresistive element 5, a second TMR magnetoresistive element 6 and a third TMR magnetoresistive element 7, output signals of the three TMR magnetoresistive elements are calculated by a resolving circuit to obtain a three-phase current value, specifically, the three TMR magnetoresistive elements are installed outside a stranded wire 4, and the TMR magnetoresistive elements can be distributed at any point outside the stranded wire. After the installation is finished, three-phase symmetrical current is introduced into the stranded wire 4, voltage signals output by the three TMR magnetoresistive elements are obtained, the analytical relation between the voltage signals and the three-phase symmetrical current is established, and a 3 x 3 nonsingular relation matrix is formed.

In actual operation, voltage signals output from the three TMR magnetoresistive elements pass through the scaling circuit, so that the value of an analog signal is within the voltage sampling range of the digital signal processor, and the value of the analog signal is converted into a digital signal value through the digital sampling circuit.

The nonsingular relation matrix takes three-phase current in the stranded wire 4 as an input variable, and voltage signals output by the three TMR magnetoresistive elements as an output variable. The relation matrix for inverting the non-singular relation matrix is a matrix which takes the voltage signals output by the three TMR magnetoresistive elements as input variables and takes three-phase current in the stranded wire 4 as output variables.

And multiplying the digital signal value serving as an input variable by the relation matrix to obtain a preliminary three-phase current value.

And (5) carrying out equal-proportion amplification on the primary three-phase current value to obtain the actual current value. Wherein the amplification ratio and the voltage signal reduction ratio of the three TMR magnetoresistive elements are inverse numbers.

The non-singular relationship matrix is determined after the installation location is confirmed and before the cable is put into actual operation.

The above are merely examples of the present invention, and the present invention is not limited to the field related to this embodiment, and the common general knowledge of the known specific structures and characteristics in the schemes is not described herein too much, and those skilled in the art can know all the common technical knowledge in the technical field before the application date or the priority date, can know all the prior art in this field, and have the ability to apply the conventional experimental means before this date, and those skilled in the art can combine their own ability to perfect and implement the scheme, and some typical known structures or known methods should not become barriers to the implementation of the present invention by those skilled in the art in light of the teaching provided in the present application. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.