CN104155499A - Current measuring device and method based on combined PCB type Rogowski coil - Google Patents

Abstract

The invention relates to a current measuring device and method based on a combined PCB Rogowski coil, including one or more pairs of PCB Rogowski coils, an amplification circuit unit, an integrating circuit unit and a sampling circuit unit, one or more pairs of PCB Rogowski coils Connected in series in sequence, the current flow direction in the winding of any two adjacent PCB Rogowski coils is opposite, and the internal through hole of the PCB Rogowski coil passes through the conductor that conducts the current, and the differential voltage signal is measured. A pair or more in series For the electrical connection of the PCB Rogowski coil to the amplifying circuit unit, the amplifying circuit unit amplifies and outputs the differential voltage signal, and the integrating circuit unit integrates the amplified differential voltage signal to obtain the restored voltage signal of the measured current in the conductor proportional to the conduction current; sampling The circuit unit samples the restored voltage signal. The invention has good parameter consistency, high reproducibility, and ensures stable mutual inductance coefficient.

Description

Current measuring device and method based on combined PCB type Rogowski coil

technical field

The invention relates to a current measuring device and method, in particular to a current measuring device and method based on a combined PCB type Rogowski coil.

Background technique

With the improvement of the operating voltage of the power grid and the improvement of reliability requirements, the traditional electromagnetic transformer not only increases in volume and weight, difficulty in explosion-proof insulation, and decline in safety performance, but also narrows the frequency band due to the existence of the iron core. The iron core will be saturated, which will cause serious distortion of the secondary signal waveform, and the dynamic range is small. When used as a relay protection, the response speed is lagging and it is easy to cause malfunction. This series of shortcomings has made it difficult for traditional electromagnetic transformers to meet the requirements of power system development. Moreover, the traditional electromagnetic transformer is difficult to solve the problems caused by its own defects due to the limitation of its working principle and manufacturing process, so it is necessary to develop a current sensor that is different from the principle of the traditional electromagnetic transformer to meet the requirements. Rogowski coil (hereinafter referred to as Rogowski coil) current transformer, as a new type of electronic current transformer, has the advantages of wide frequency measurement, high precision, large measurement range, no magnetic saturation, easy digital output, and small size. It has become a modern One of the important directions for the development of current transformers has broad prospects for development in power systems.

However, the traditional Rogowski coils that are currently in use have low measurement accuracy and stability, are troublesome to manufacture, and have a large dispersion of product performance, which is not conducive to large-scale industrial production and cannot meet the requirements of current power system construction.

Contents of the invention

The purpose of the present invention is to provide a current measuring device and method based on a combined PCB type Rogowski coil, which solves the problem that the measurement accuracy and stability of the traditional Rogowski coil are not high, the production is troublesome, and the product performance is highly dispersed, which is not conducive to The problem of large-scale industrial production.

In order to solve the above problems, the present invention relates to a current measuring device based on a combined PCB type Rogowski coil, which measures a conductor conducting current, including one or more pairs of PCB type Rogowski coils, an amplifying circuit unit, and an integrating circuit unit and a sampling circuit unit, wherein:

The PCB-type Rogowski coils all include a PCB board, internal through holes and windings on the PCB board, and the one or more pairs of PCB-type Rogowski coils are the number of winding turns, the height of the skeleton, the outer diameter of the skeleton and the inner diameter of the skeleton. As well as PCB-type Rogowski coils with the same inner diameter of the internal through-holes, the PCB boards of two adjacent PCB-type Rogowski coils are arranged parallel to each other and at equal intervals, and the connection lines of the centers of the internal through-holes of all PCB-type Rogowski coils are on the same straight line , and the straight line is in the same direction as the axial direction of the internal through hole of the PCB type Rogowski coil; the one or more pairs of PCB Rogowski coils are connected in series in sequence, and the current flows in the windings of any two adjacent PCB Rogowski coils The directions are opposite, clockwise and counterclockwise respectively; the internal through holes of the one or more pairs of PCB Rogowski coils pass through the conductors conducting the current, and the differential voltage signals are measured. Or one end of multiple pairs of PCB Rogowski coils is grounded;

The other end of the one or more pairs of PCB Rogowski coils in series is electrically connected to an amplifying circuit unit, and the amplifying circuit unit amplifies and outputs the differential voltage signal;

The integrating circuit unit is electrically connected to the amplifying circuit unit, and integrates the amplified differential voltage signal to obtain a restored voltage signal proportional to the measured current in the conductor of the conduction current;

The sampling circuit unit is electrically connected to the integrating circuit unit to sample the restored voltage signal.

Preferably, a fixing device is also included to fix the one or more pairs of PCB Rogowski coils parallel to each other and equidistant from each other.

Preferably, the amplifying circuit unit is a non-inverting input amplifying circuit, including a first integrated operational amplifier, a first resistor, a second resistor, and a third resistor; one end of the first resistor is electrically connected to the one or more pairs of The signal output end of the PCB Rogowski coil, the other end is electrically connected to the positive input end of the first integrated operational amplifier; one end of the second resistor is grounded, and the other end is electrically connected to the reverse input end of the first integrated operational amplifier ; One end of the third resistor is electrically connected to the output end of the first integrated operational amplifier, and the other end is electrically connected to the inverting input end of the first integrated operational amplifier.

Preferably, the integral circuit unit is an integral operation circuit, including a second integrated operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor, and a first capacitor; one end of the fourth resistor is electrically connected to the first The output end of the second integrated operational amplifier, the other end is electrically connected to the positive input end of the second integrated operational amplifier; one end of the fifth resistor is electrically connected to the output end of the second integrated operational amplifier, and the other end is electrically connected to the second integrated operational amplifier. The positive input terminal of the second integrated operational amplifier; the two ends of the first capacitor are connected in parallel to the two ends of the fifth resistor; one end of the sixth resistor is electrically connected to the reverse input of the second integrated operational amplifier terminal, and the other terminal is grounded; the output terminal of the second integrated operational amplifier is connected to the sampling circuit unit.

Preferably, both the first integrated operational amplifier and the second integrated operational amplifier use OP07CP.

In order to achieve the above object, the present invention also relates to a current measurement method based on a combined PCB type Rogowski coil, comprising the following steps:

Connect one or more pairs of PCB-type Rogowski coils with the same number of winding turns, skeleton height, skeleton outer diameter, skeleton inner diameter and internal through-hole inner diameter in series, so that the current in the winding of any two adjacent PCB Rogowski coils The flow direction is opposite, clockwise and counterclockwise respectively;

The PCB-type Rogowski coil is fixed by a fixing device, so that the PCB boards of two adjacent PCB-type Rogowski coils are parallel and equidistant from each other, and the connecting lines of the centers of the through holes in all PCB-type Rogowski coils are on the same straight line, and The straight line is in the same direction as the axial direction of the internal through hole of the PCB type Rogowski coil;

Pass a conductor under test through the internal through holes of all PCB Rogowski coils;

After the conductor under test conducts the current, a differential voltage signal is measured through the PCB type Rogowski coil electrically connected in series;

The one or more pairs of PCB Rogowski coils connected in series are electrically connected through an amplifying circuit unit, and the differential voltage signal is amplified and output;

The amplifying circuit unit is electrically connected to the amplifying circuit unit through the integrating circuit unit, and the amplified differential voltage signal is integrated to obtain a restored voltage signal proportional to the measured current in the conductor of the conduction current;

The integration circuit unit is electrically connected to the sampling circuit unit to sample the restored voltage signal.

Preferably, the amplifying circuit unit is a non-inverting input amplifying circuit, including a first integrated operational amplifier, a first resistor, a second resistor and a third resistor; one end of the first resistor is electrically connected to the one or more pairs The signal output end of the PCB Rogowski coil, the other end is electrically connected to the positive input end of the first integrated operational amplifier; one end of the second resistor is grounded, and the other end is electrically connected to the reverse input end of the first integrated operational amplifier ; One end of the third resistor is electrically connected to the output end of the first integrated operational amplifier, and the other end is electrically connected to the inverting input end of the first integrated operational amplifier.

Preferably, the integral circuit unit is an integral operation circuit, including a second integrated operational amplifier, a fourth resistor, a fifth resistor, a sixth resistor, and a first capacitor; one end of the fourth resistor is electrically connected to the first The output end of the second integrated operational amplifier, the other end is electrically connected to the positive input end of the second integrated operational amplifier; one end of the fifth resistor is electrically connected to the output end of the second integrated operational amplifier, and the other end is electrically connected to the second integrated operational amplifier. The positive input terminal of the second integrated operational amplifier; the two ends of the first capacitor are connected in parallel to the two ends of the fifth resistor; one end of the sixth resistor is electrically connected to the reverse input of the second integrated operational amplifier terminal, and the other terminal is grounded; the output terminal of the second integrated operational amplifier is connected to the sampling circuit unit.

Preferably, both the first integrated operational amplifier and the second integrated operational amplifier use OP07CP.

Compared with the prior art, the present invention has the following advantages and positive effects due to the adoption of the above technical scheme:

The PCB-type Rogowski coil provided in the present invention has good parameter consistency and high reproducibility, ensures stable mutual inductance coefficient, and is easy to produce on a large scale. Moreover, the anti-interference ability is strong, and the frequency bandwidth of current measurement can meet the accuracy and reliability requirements of the power system for current measurement. At the same time, the production cost is low, and it can meet the accuracy and reliability requirements of the power system for current measurement.

Description of drawings

Fig. 1 is the block diagram of a kind of current measuring device based on combined PCB type Rogowski coil of the present invention;

Fig. 2 is the connection schematic diagram of arbitrary two PCB type Rogowski coils in the embodiment of the present invention;

Fig. 3 is a circuit structure diagram of an amplifying circuit unit in an embodiment of the present invention;

Fig. 4 is the circuit structural diagram of the integral circuit unit in the embodiment of the present invention;

Fig. 5 is the schematic circuit diagram of one or more pairs of PCB Rogowski coils of the present invention;

FIG. 6 is a flowchart of a current measurement method based on a combined PCB type Rogowski coil in an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Obviously, what is described here is only a part of the examples of the present invention, not all examples. Based on the implementation of the present invention For example, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In order to facilitate the understanding of the embodiments of the present invention, specific embodiments will be taken as examples for further explanation below in conjunction with the accompanying drawings, and each embodiment does not constitute a limitation to the embodiments of the present invention.

As shown in attached drawings 1-5, a current measuring device based on a combined PCB type Rogowski coil measures a conductor conducting current, including one or more pairs of PCB type Rogowski coils, an amplifying circuit unit, and an integrating circuit unit and a sampling circuit unit, wherein:

A PCB type Rogowski coil includes a PCB board, internal through holes and windings on the PCB board. The mutual inductance coefficient of the coil is proportional to the number of winding turns, the height of the skeleton, the outer diameter of the skeleton and the inner diameter of the skeleton. One or more pairs of PCB type Rogowski coils are the number of winding turns, the height of the skeleton, the outer diameter of the skeleton, the inner diameter of the skeleton and the internal through hole PCB-type Rogowski coils with the same inner diameter r.

In this embodiment, 2 pairs of PCB-type Rogowski coils are used, and the skeleton height of the PCB-type Rogowski coils is the thickness of the PCB board, except for special requirements. Generally, the thickness of the board does not exceed 3.2mm. Considering the comprehensive production factor, 2mm is more appropriate.

The PCB boards of two adjacent PCB-type Rogowski coils are arranged in parallel with each other at equal intervals, and the connecting lines of the centers of the internal through holes of all PCB-type Rogowski coils are on the same straight line, and the straight line is in line with the inside of the PCB-type Rogowski coils. The axial directions of the through holes are in the same direction. One or more pairs of PCB Rogowski coils are connected in series in sequence, and the current flow directions in the windings of any two adjacent PCB Rogowski coils are opposite, clockwise and counterclockwise respectively. According to the law of electromagnetic induction, even if there is an external magnetic field, the voltage induced on two adjacent coils is the same, but the direction of the two is opposite, so the combined effect of the external magnetic field does not exist, and the two cancel each other out. However, the voltage induced by the magnetic field of the measured current is in the same direction, and the total induced electromotive force after series connection is the sum of the respective induced electromotive forces of the coils connected in series. Therefore, not only the interference of the external magnetic field is reduced or even eliminated, but also the mutual inductance coefficient of the coil will increase exponentially with the increase of the number of serial PCB boards.

The internal through holes of all PCB Rogowski coils pass through the current-conducting conductors, and the differential voltage signal is measured. One end of one or more pairs of PCB Rogowski coils in series is grounded, and the other end of one or more pairs of PCB Rogowski coils in series The amplifying circuit unit is electrically connected, and the amplifying circuit unit amplifies and outputs the differential voltage signal.

In this embodiment, the amplifying circuit unit is a non-inverting input amplifying circuit, including a first integrated operational amplifier, a first resistor Rp, a second resistor R1, and a third resistor R2; wherein the first integrated operational amplifier adopts OP07CP, and the integrated operational amplifier It is characterized by dual power supply, high precision, small temperature drift, superior comprehensive performance and wide application range. The relatively weak signal output by the Rogowski coil is amplified without distortion through the amplifying circuit unit to meet the signal strength requirements of the subsequent circuit.

One end of the first resistor is electrically connected to the signal output ends of one or more pairs of PCB Rogowski coils, and the other end is electrically connected to the positive input end of the first integrated operational amplifier. One end of the second resistor is grounded, and the other end is electrically connected to the reverse input end of the first integrated operational amplifier. One end of the third resistor is electrically connected to the output end of the first integrated operational amplifier, and the other end is electrically connected to the inverting input end of the first integrated operational amplifier.

The integrating circuit unit is electrically connected with the amplifying circuit unit, integrates the amplified differential voltage signal, and obtains a restored voltage signal proportional to the measured current in the conductor which conducts the current.

In this embodiment, the integral circuit unit is an integral operation circuit, including a second integrated operational amplifier, a fourth resistor Rf, a fifth resistor R, a sixth resistor Rp2, and a first capacitor C; the integral circuit unit uses an inertial link instead of an ideal integral link, the fourth resistor Rf and the first capacitor C form an RC loop, which prevents the DC and low-frequency signals from saturating the output of the integrator, thereby avoiding the influence of integral drift. Among them, the second integrated operational amplifier adopts OP07CP, and adopts the approximate integral action of the inertial link, which realizes the suppression of integral drift, stabilizes the operating point, and controls the error within the allowable range. One end of the fourth resistor is electrically connected to the output end of the second integrated operational amplifier, and the other end is electrically connected to the positive input end of the second integrated operational amplifier; one end of the fifth resistor is electrically connected to the output end of the second integrated operational amplifier, and the other end is electrically connected to the positive input end of the second integrated operational amplifier. One end is electrically connected to the positive input end of the second integrated operational amplifier; both ends of the first capacitor are connected in parallel to both ends of the fifth resistor; one end of the sixth resistor is electrically connected to the reverse input end of the second integrated operational amplifier, and the other end is grounded; The output end of the second integrated operational amplifier is connected to the sampling circuit unit.

The sampling circuit unit is electrically connected to the integrating circuit unit to sample the restored voltage signal.

Including the fixing device, fixing one or more pairs of PCB Rogowski coils in parallel with each other at equal intervals, and also including fixing one or more pairs of PCB Rogowski coils next to each other. Many kinds of fixing mechanisms can be used, such as clips, equidistant Card slots, insulating tapes, etc. are all available and are not limited.

In the present invention, the measurement range can be from a few amperes to tens of thousands of amperes. A better way is to change the resistance ratio of the amplification link and the integration link according to the size of the specific measurement object during the specific design, so as to achieve the measured current Range of higher precision.

As shown in Figure 5, where: i ₁ (t) represents the measured current at the primary side; L ₀ represents the total self-inductance of one or more pairs of PCB Rogowski coils; R ₀ represents the internal resistance of the coil; C ₀ represents the inter-turn capacitance of the coil; R _a is the sampling resistor. From this equivalent circuit diagram, the following equation can be obtained:

The induced electromotive force e(t) of the coil can be expressed as:

$\mathrm{<span\; class="notranslate">\; e</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; di</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

The mutual inductance coefficient between the Rogowski coil and the current-carrying wire is:

$\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\mathrm{<span\; class="notranslate">\; n</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}\mathrm{<span\; class="notranslate">\; ln</span>}\frac{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}}$

Among the above types:

i——instantaneous current flowing in the current-carrying wire, unit A;

μ ₀ ——vacuum magnetic permeability, μ ₀ =4π×10 ^-7 H/m;

r _a —outer diameter of the frame, in m;

r _b — inner diameter of skeleton, unit m;

h——skeleton height, unit m;

N - the number of turns of the coil winding.

The output voltage on the sampling resistor R _a is:

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\mathrm{<span\; class="notranslate">\; m</span>}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; di</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; dt</span>}}$

In the non-inverting amplifier circuit, the magnification factor is:

${\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; u</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}$

The transfer function of the inertia link composed of Rf and C and the second integrated operational amplifier is:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}\mathrm{<span\; class="notranslate">\; Cs</span>}}$

Let s=jω, then the above formula can be transformed into:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}\mathrm{<span\; class="notranslate">\; Cj\&omega;</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}\mathrm{<span\; class="notranslate">\; Cj\&omega;</span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

The magnitude-frequency response is:

$<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; |</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}{\mathrm{<span\; class="notranslate">\; R</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}$

The phase-frequency response is:

So the transfer function of the ideal integrator is:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; RCs</span>}}$

The present invention also provides a current measuring method based on a combined PCB type Rogowski coil, comprising the following steps:

Connect one or more pairs of PCB-type Rogowski coils with the same number of winding turns, skeleton height, skeleton outer diameter, skeleton inner diameter and internal through-hole inner diameter in series, so that the current in the winding of any two adjacent PCB Rogowski coils The flow directions are opposite, clockwise and counterclockwise, respectively.

The PCB-type Rogowski coil is fixed by a fixing device, so that the PCB boards of two adjacent PCB-type Rogowski coils are parallel and equidistant from each other, and the connecting lines of the centers of the through holes in all PCB-type Rogowski coils are on the same straight line, and The straight line is in the same direction as the axial direction of the internal through hole of the PCB type Rogowski coil. According to the law of electromagnetic induction, even if there is an external magnetic field, the voltage induced on two adjacent coils is the same, but the direction of the two is opposite, so the combined effect of the external magnetic field does not exist, and the two cancel each other out. However, the voltage induced by the magnetic field of the measured current is in the same direction, and the total induced electromotive force after series connection is the sum of the respective induced electromotive forces of the coils connected in series. Therefore, not only the interference of the external magnetic field is reduced or even eliminated, but also the mutual inductance coefficient of the coil will increase exponentially with the increase of the number of serial PCB boards.

Pass a conductor under test through the internal through holes of all PCB Rogowski coils;

After the conductor under test conducts the current, a differential voltage signal is measured through the PCB type Rogowski coil electrically connected in series;

The one or more pairs of PCB Rogowski coils connected in series are electrically connected through an amplifying circuit unit to amplify and output the differential voltage signal.

In this embodiment, the amplifying circuit unit is a non-inverting input amplifying circuit, including a first integrated operational amplifier, a first resistor Rp, a second resistor R1 and a third resistor R3; wherein the first integrated operational amplifier adopts OP07CP, and the integrated operational amplifier It is characterized by dual power supply, high precision, small temperature drift, superior comprehensive performance and wide application range. The relatively weak signal output by the Rogowski coil is amplified without distortion through the amplifying circuit unit to meet the signal strength requirements of the subsequent circuit. One end of the first resistor is electrically connected to the signal output ends of one or more pairs of PCB Rogowski coils, and the other end is electrically connected to the positive input end of the first integrated operational amplifier. One end of the second resistor is grounded, and the other end is electrically connected to the reverse input end of the first integrated operational amplifier. One end of the third resistor is electrically connected to the output end of the first integrated operational amplifier, and the other end is electrically connected to the inverting input end of the first integrated operational amplifier.

The amplifying circuit unit is electrically connected to the amplifying circuit unit through the integrating circuit unit, and the amplified differential voltage signal is integrated to obtain a restored voltage signal of the measured current in the conductor proportional to the conduction current.

In this embodiment, the integral circuit unit is an integral operation circuit, including a second integrated operational amplifier, a fourth resistor Rf, a fifth resistor R, a sixth resistor Rp2, and a first capacitor C; the integral circuit unit uses an inertial link instead of an ideal integral link, the fourth resistor Rf and the first capacitor C form an RC loop, which prevents the DC and low-frequency signals from saturating the output of the integrator, thereby avoiding the influence of integral drift. Among them, the second integrated operational amplifier adopts OP07CP, and adopts the approximate integral action of the inertial link, which realizes the suppression of integral drift, stabilizes the operating point, and controls the error within the allowable range. One end of the fourth resistor is electrically connected to the output end of the second integrated operational amplifier, and the other end is electrically connected to the positive input end of the second integrated operational amplifier; one end of the fifth resistor is electrically connected to the output end of the second integrated operational amplifier, and the other end is electrically connected to the positive input end of the second integrated operational amplifier. One end is electrically connected to the positive input end of the second integrated operational amplifier; both ends of the first capacitor are connected in parallel to both ends of the fifth resistor; one end of the sixth resistor is electrically connected to the reverse input end of the second integrated operational amplifier, and the other end is grounded; The output end of the second integrated operational amplifier is connected to the sampling circuit unit.

The integral circuit unit is electrically connected to the sampling circuit unit to sample the restored voltage signal.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (9)

1. A current measuring device based on a combined PCB type Rogowski coil, for the measurement of a conduction current conductor, it is characterized in that it includes one or more pairs of PCB type Rogowski coils, amplifying circuit units, integrating circuit units and sampling circuits unit, where: The PCB-type Rogowski coils all include a PCB board, internal through holes and windings on the PCB board, and the one or more pairs of PCB-type Rogowski coils are the number of winding turns, the height of the skeleton, the outer diameter of the skeleton and the inner diameter of the skeleton. As well as PCB-type Rogowski coils with the same inner diameter of the internal through-holes, the PCB boards of two adjacent PCB-type Rogowski coils are arranged parallel to each other and at equal intervals, and the connection lines of the centers of the internal through-holes of all PCB-type Rogowski coils are on the same straight line , and the straight line is in the same direction as the axial direction of the internal through hole of the PCB type Rogowski coil; the one or more pairs of PCB Rogowski coils are connected in series in sequence, and the current flows in the windings of any two adjacent PCB Rogowski coils The directions are opposite, clockwise and counterclockwise respectively; the internal through holes of the one or more pairs of PCB Rogowski coils pass through the conductors conducting the current, and the differential voltage signals are measured. Or one end of multiple pairs of PCB Rogowski coils is grounded; The other end of the one or more pairs of PCB Rogowski coils in series is electrically connected to an amplifying circuit unit, and the amplifying circuit unit amplifies and outputs the differential voltage signal; The integrating circuit unit is electrically connected to the amplifying circuit unit, and integrates the amplified differential voltage signal to obtain a restored voltage signal proportional to the measured current in the conductor of the conduction current; The sampling circuit unit is electrically connected to the integrating circuit unit to sample the restored voltage signal.              2. A kind of current measuring device based on combined PCB type Rogowski coils as claimed in claim 1, is characterized in that, also comprises a fixing device, described one or more pairs of PCB Rogowski coils are mutually parallel and equidistantly fixed . 3. A kind of current measuring device based on combined PCB type Rogowski coil as claimed in claim 1 or 2, wherein the amplifying circuit unit is a non-inverting input amplifying circuit, comprising a first integrated operational amplifier, a first resistor, The second resistance and the third resistance; one end of the first resistance is electrically connected to the signal output end of the one or more pairs of PCB Rogowski coils, and the other end is electrically connected to the positive input end of the first integrated operational amplifier; One end of the second resistor is grounded, and the other end is electrically connected to the reverse input end of the first integrated operational amplifier; one end of the third resistor is electrically connected to the output end of the first integrated operational amplifier, and the other end is electrically connected to the The inverting input terminal of the first integrated operational amplifier. 4. a kind of current measuring device based on combined PCB type Rogowski coil as claimed in claim 3, is characterized in that, described integral circuit unit is an integral operation circuit, comprises the second integrated operational amplifier, the 4th resistor, the 4th resistor. Five resistors, a sixth resistor, and a first capacitor; one end of the fourth resistor is electrically connected to the output end of the second integrated operational amplifier, and the other end is electrically connected to the positive input end of the second integrated operational amplifier; the One end of the fifth resistor is electrically connected to the output end of the second integrated operational amplifier, and the other end is electrically connected to the positive input end of the second integrated operational amplifier; both ends of the first capacitor are connected in parallel to the fifth resistor Two ends; one end of the sixth resistor is electrically connected to the inverting input end of the second integrated operational amplifier, and the other end is grounded; the output end of the second integrated operational amplifier is connected to the sampling circuit unit. 5. a kind of current measuring device based on combined PCB type Rogowski coil as claimed in claim 4, is characterized in that, described first integrated op-amp and the second integrated op-amp all adopt OP07CP. 6. A current measurement method based on a combined PCB type Rogowski coil, characterized in that, comprising the following steps: Connect one or more pairs of PCB-type Rogowski coils with the same number of winding turns, skeleton height, skeleton outer diameter, skeleton inner diameter and internal through-hole inner diameter in series, so that the current in the winding of any two adjacent PCB Rogowski coils The flow direction is opposite, clockwise and counterclockwise respectively; The PCB-type Rogowski coil is fixed by a fixing device, so that the PCB boards of two adjacent PCB-type Rogowski coils are parallel and equidistant from each other, and the connecting lines of the centers of the through holes in all PCB-type Rogowski coils are on the same straight line, and The straight line is in the same direction as the axial direction of the internal through hole of the PCB type Rogowski coil; Pass a conductor under test through the internal through holes of all PCB Rogowski coils; After the conductor under test conducts the current, a differential voltage signal is measured through the PCB type Rogowski coil electrically connected in series; The one or more pairs of PCB Rogowski coils connected in series are electrically connected through an amplifying circuit unit, and the differential voltage signal is amplified and output; The amplifying circuit unit is electrically connected to the amplifying circuit unit through the integrating circuit unit, and the amplified differential voltage signal is integrated to obtain a restored voltage signal proportional to the measured current in the conductor of the conduction current; The integration circuit unit is electrically connected to the sampling circuit unit to sample the restored voltage signal. 7. a kind of current measurement method based on combined PCB type Rogowski coil as claimed in claim 6, is characterized in that, described amplifying circuit unit is a non-inverting input amplifying circuit, comprises the first integrated operational amplifier, the first resistance, the first Two resistors and a third resistor; one end of the first resistor is electrically connected to the signal output ends of the one or more pairs of PCB Rogowski coils, and the other end is electrically connected to the positive input end of the first integrated operational amplifier; One end of the second resistor is grounded, and the other end is electrically connected to the reverse input end of the first integrated operational amplifier; one end of the third resistor is electrically connected to the output end of the first integrated operational amplifier, and the other end is electrically connected to the Inverting input of the first integrated operational amplifier. 8. a kind of current measuring method based on combined PCB type Rogowski coil as claimed in claim 6 or 7, is characterized in that, described integral circuit unit is an integral operation circuit, comprises the second integrated operational amplifier, the 4th resistor , the fifth resistor, the sixth resistor and the first capacitor; one end of the fourth resistor is electrically connected to the output end of the second integrated operational amplifier, and the other end is electrically connected to the positive input end of the second integrated operational amplifier; One end of the fifth resistor is electrically connected to the output end of the second integrated operational amplifier, and the other end is electrically connected to the positive input end of the second integrated operational amplifier; both ends of the first capacitor are connected in parallel to the fifth Two ends of the resistor; one end of the sixth resistor is electrically connected to the reverse input end of the second integrated operational amplifier, and the other end is grounded; the output end of the second integrated operational amplifier is connected to the sampling circuit unit. 9. a kind of current measuring method based on combined PCB type Rogowski coil as claimed in claim 8, is characterized in that, described first integrated op-amp and the second integrated op-amp all adopt OP07CP.