阅读说明：本技术 一种基于罗氏线圈的电流测量方法及装置 (Current measuring method and device based on Rogowski coil ) 是由 刘毅 潘曦宇 周婧 林福昌 丁黎 龙兆芝 李文婷 谢施君 于 2020-12-19 设计创作，主要内容包括：本发明提供了一种基于罗氏线圈的电流测量方法及装置,属于电流测量领域,电流测量方法包括：将罗氏线圈的其中一条绕线作为主绕线,剩余绕线作为副绕线；罗氏线圈是同向绕制绕线而成,其绕线数量使罗氏线圈满足外积分电路的条件；将主绕线的输出端与第一运算放大器相连；且将副绕线之间进行加法运算后,与第二运算放大器相连,获取第二运算放大器的输出电压；将第一运算放大器的输出电压与第二运算放大器的输出电压进行差分处理后,计算输出电流；其中,主绕线输出电压与副绕线加法运算后的输出电压以异相的形式分别输入至第一运算放大器和第二运算放大器。本发明强化罗氏线圈稳定性的同时降低了运算放大器失调电压的影响,实现了电流的准确测量。(The invention provides a current measuring method and a device based on a Rogowski coil, belonging to the field of current measurement, wherein the current measuring method comprises the following steps: one winding of the Rogowski coil is used as a main winding, and the rest windings are used as auxiliary windings; the Rogowski coil is formed by winding in the same direction, and the number of the windings enables the Rogowski coil to meet the condition of an external integration circuit; connecting the output end of the main winding with a first operational amplifier; after addition operation is carried out between the secondary windings, the secondary windings are connected with a second operational amplifier to obtain the output voltage of the second operational amplifier; calculating output current after performing difference processing on the output voltage of the first operational amplifier and the output voltage of the second operational amplifier; the output voltage of the main winding and the output voltage obtained after the addition operation of the auxiliary winding are respectively input to the first operational amplifier and the second operational amplifier in an out-of-phase mode. The invention strengthens the stability of the Rogowski coil, reduces the influence of offset voltage of the operational amplifier and realizes accurate measurement of current.)

1. A current measuring method based on a Rogowski coil is characterized by comprising the following steps:

one winding of the Rogowski coil is used as a main winding, and the rest windings are used as auxiliary windings; the Rogowski coil is formed by winding in the same direction, and the number of the windings enables the Rogowski coil to meet the condition of an external integration circuit;

connecting the output end of the main winding with a first operational amplifier; and after the addition operation is carried out between the auxiliary windings, the auxiliary windings are connected with a second operational amplifier;

calculating output current after performing difference processing on the output voltage of the first operational amplifier and the output voltage of the second operational amplifier;

the output voltage of the main winding and the output voltage obtained after the addition operation of the auxiliary winding are respectively input to the first operational amplifier and the second operational amplifier in an out-of-phase mode.

2. The current measuring method according to claim 1, wherein the number of windings of the rogowski coil is obtained by:

based on the frequency of the measured signal and an external sampling resistor, acquiring the number of turns of each winding under the condition that the Rogowski coil is an external integrating circuit;

and acquiring the number of the windings by using the number of the windings and the diameter of the framework.

3. The current measuring method according to claim 1 or 2, wherein the condition that the rogowski coil is an outer integration circuit is:

ωL<<R₀

wherein, ω is 2 × pi × f, f is the measured signal; l is a single-winding inductance on the Rogowski coil; r₀Is externally connected with a sampling resistor.

4. The method of current measurement according to claim 3, wherein the number of windings is a maximum value rounded down by 2 x pi x d/Ns; wherein d is the distance between the measured lead and the center of the Rogowski coil; s is the diameter of a single winding; n is the number of turns per winding.

5. A current measuring apparatus based on the current measuring method according to claim 1, comprising a first operational amplifier, a second operational amplifier, a differential circuit, a rogowski coil constructing unit, and a calculating unit;

the input end of the differential circuit is connected with the output end of the first operational amplifier and the output end of the second operational amplifier;

when the operational amplifier is used, the first operational amplifier is connected with the output end of the Rogowski coil main winding to obtain the output voltage of the first operational amplifier;

when in use, the auxiliary windings of the Rogowski coil are subjected to addition operation and then connected with the second operational amplifier to obtain the output voltage of the second operational amplifier;

the differential circuit is used for carrying out differential processing on the output voltage of the first operational amplifier and the output voltage of the second operational amplifier;

the calculating unit is used for calculating the number of windings of the Rogowski coil under the condition that the Rogowski coil is an external integration circuit; calculating output current according to the difference result;

the Rogowski coil construction unit is used for winding the windings in the same direction based on the number of the windings to obtain the Rogowski coil, selecting one winding as a main winding, and using the rest windings as auxiliary windings;

the output voltage of the main winding and the output voltage obtained after the addition operation of the auxiliary winding are respectively input to the first operational amplifier and the second operational amplifier in an out-of-phase mode.

6. The current measuring device according to claim 5, wherein the number of windings of the Rogowski coil is calculated by:

based on the frequency of the measured signal and an external sampling resistor, acquiring the number of turns of each winding under the condition that the Rogowski coil is an external integrating circuit;

and acquiring the number of the windings by using the number of the windings and the diameter of the framework.

7. Current measurement device according to claim 5 or 6, characterized in that the condition for the Rogowski coil being an outer integrating circuit is: omega L<<R₀(ii) a Wherein, ω is 2 × pi × f, f is the measured signal; l is a single-winding inductance on the Rogowski coil; r₀Is externally connected with a sampling resistor.

8. Current measuring device according to claim 5 or 6, characterised in that the number of windings is a maximum value rounded down by 2 x pi x d/Ns; wherein d is the distance between the measured lead and the center of the Rogowski coil; s is the diameter of a single winding; n is the number of turns per winding.

9. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 4.

Technical Field

The invention belongs to the field of current measurement, and particularly relates to a current measurement method and device based on a Rogowski coil.

Background

The pulse current has the characteristics of large waveform gradient and short duration, so that the requirement on the measurement precision is high, and meanwhile, the pulse current generator is increasingly miniaturized, so that the Rogowski coil is widely applied to the field of pulse current measurement.

For the traditional self-integration rogowski coil, because the self-inductance value of the rogowski coil is far larger than the sum of the sampling resistance value and the coil resistance value, the rogowski coil containing an iron core is often adopted to meet the integration condition of self-integration, and the saturation characteristic of the iron core and the stability problem caused by manually winding the coil cause people to pay attention to the external integration rogowski coil.

Correspondingly, the external integral rogowski coil needs to satisfy the integral condition of external integral, wherein the external integral condition is constrained by the inner and outer diameters of the framework, the wire diameter and the like, the current measurement of a specific cable is limited by the outer diameter of the framework, the inductance value of the rogowski coil can be adjusted only by changing the number of turns of the coil, and the adjustment mode usually causes that the coil is not necessarily in a close-wound state, so that the current measurement effect of the rogowski coil is unstable.

Meanwhile, external integration means that the output voltage of the rogowski coil needs to be resampled first and then integrated by an external operational amplifier, and the operational amplifier has input offset voltage, so that signal offset caused by the offset voltage exists in a traditional active integration loop, and the real waveform of the measured current cannot be accurately reflected.

Disclosure of Invention

The invention aims to provide a current measuring method and device based on a rogowski coil, aiming at solving the problem that the accuracy of the current measured by the rogowski coil is not high due to the fact that a framework cannot be adjusted and an operational amplifier is out of order when the current is measured by the rogowski coil.

In order to achieve the above object, the present invention provides a current measuring method based on a rogowski coil, comprising the following steps:

one winding of the Rogowski coil is used as a main winding, and the rest windings are used as auxiliary windings; the Rogowski coil is formed by winding in the same direction, and the number of the windings enables the Rogowski coil to meet the condition of an external integration circuit;

connecting the output end of the main winding with a first operational amplifier to obtain the output voltage of the first operational amplifier;

after addition operation is carried out between the secondary windings, the secondary windings are connected with a second operational amplifier to obtain the output voltage of the second operational amplifier;

calculating output current after performing difference processing on the output voltage of the first operational amplifier and the output voltage of the second operational amplifier;

the output voltage of the main winding and the output voltage obtained after the addition operation of the auxiliary winding are respectively input to the first operational amplifier and the second operational amplifier in an out-of-phase mode.

Preferably, the method for acquiring the number of windings of the rogowski coil comprises the following steps:

based on the frequency of the measured signal and an external sampling resistor, acquiring the number of turns of each winding under the condition that the Rogowski coil is an external integrating circuit;

and acquiring the number of the windings by using the number of the windings and the diameter of the framework.

Preferably, the condition that the rogowski coil is an outer integration circuit is: omega L<<R₀(ii) a Wherein, ω is 2 × pi × f, f is the measured signal; l is a single-winding inductance on the Rogowski coil; r₀Is externally connected with a sampling resistor.

Preferably, the number of windings is a maximum rounded down by 2 × pi × d/Ns; d is the distance (skeleton diameter) between the measured lead and the center of the Rogowski coil; s is the diameter of a single winding; n is the number of turns per winding.

Based on the current measuring method of the Rogowski coil, the invention provides a corresponding current measuring device, which comprises the following steps: the device comprises a first operational amplifier, a second operational amplifier, a Rogowski coil construction unit, a differential circuit and a calculation unit;

the input end of the differential circuit is connected with the output end of the first operational amplifier and the output end of the second operational amplifier;

when the operational amplifier is used, the first operational amplifier is connected with the output end of the Rogowski coil main winding to obtain the output voltage of the first operational amplifier;

when in use, the auxiliary windings of the Rogowski coil are added and then connected with a second operational amplifier to obtain the output voltage of the second operational amplifier;

the differential circuit is used for carrying out differential processing on the output voltage of the first operational amplifier and the output voltage of the second operational amplifier;

the calculation unit is used for calculating the number of windings of the Rogowski coil under the condition that the Rogowski coil is an external integration circuit; calculating output current according to the difference result;

the Rogowski coil construction unit is used for winding the windings in the same direction based on the obtained number of the windings to obtain the Rogowski coil, selecting one of the windings as a main winding, and using the rest windings as an auxiliary winding;

the output voltage of the main winding and the output voltage obtained after the addition operation of the auxiliary winding are respectively input to the first operational amplifier and the second operational amplifier in an out-of-phase mode.

Preferably, the calculation method of the number of windings of the rogowski coil is as follows:

based on the frequency of the measured signal and an external sampling resistor, acquiring the number of turns of each winding under the condition that the Rogowski coil is an external integrating circuit;

and acquiring the number of the windings by using the number of the windings and the diameter of the framework.

Preferably, the condition that the rogowski coil is an outer integration circuit is: omega L<<R₀(ii) a Wherein, ω is 2 × pi × f, f is the measured signal; l is a single-winding inductance on the Rogowski coil; r₀Is externally connected with a sampling resistor.

Preferably, the number of windings is a maximum rounded down by 2 × pi × d/Ns; wherein d is the distance (skeleton diameter) between the measured lead and the center of the Rogowski coil; s is the diameter of a single winding; n is the number of turns per winding.

The rogowski coil-based current measurement method disclosed herein may be stored in a computer-readable storage medium, on which a computer program is stored, which, when executed by a processor, may perform the steps of the current measurement method.

Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

the Rogowski coil is obtained by obtaining the number of windings of the Rogowski coil under the condition that the Rogowski coil is an external integration circuit and winding the windings in the same direction based on the number of the windings, so that the problem that the traditional framework is not adjustable is solved, and the stability of the Rogowski coil is enhanced. Meanwhile, the output end of the main winding is connected with a first operational amplifier, and after addition operation is carried out on the auxiliary windings, the main winding is connected with a second operational amplifier to obtain the output voltage of the second operational amplifier; calculating output current after performing difference processing on the output voltage of the first operational amplifier and the output voltage of the second operational amplifier; the integrating circuit corresponding to the Rogowski coil is completed, the influence of offset voltage of the operational amplifier is reduced by the integrating circuit, the accuracy of a final current measurement value is improved, and the primary side current waveform is convenient to restore.

Drawings

FIG. 1 is a schematic diagram of a Rogowski coil-based current measurement method provided by the present invention;

FIG. 2 is a schematic diagram of a multi-winding Rogowski coil provided in accordance with an embodiment of the present invention;

FIG. 3 is an integrating circuit corresponding to the main winding according to the embodiment of the present invention;

FIG. 4 is a diagram of an adder and an integrator corresponding to secondary windings provided by an embodiment of the present invention;

fig. 5 is a differential circuit in which the main winding and the sub-winding provided in the embodiment of the present invention are output after passing through the integrating circuit.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1, the present invention provides a current measuring method based on rogowski coil, comprising the following steps:

acquiring the number of windings of the Rogowski coil under the condition that the Rogowski coil meets an external integration circuit;

winding in the same direction to obtain the Rogowski coil based on the number of windings, taking one winding of the Rogowski coil as a main winding, and taking the rest windings as auxiliary windings;

connecting the output end of the main winding with a first operational amplifier to obtain the output voltage of the first operational amplifier;

after addition operation is carried out between the secondary windings, the secondary windings are connected with a second operational amplifier to obtain the output voltage of the second operational amplifier;

calculating output current after performing difference processing on the output voltage of the first operational amplifier and the output voltage of the second operational amplifier;

the output voltage of the main winding and the output voltage obtained after the addition operation of the auxiliary winding are respectively input to a first operational amplifier and a second operational amplifier in an out-of-phase mode; the Rogowski coil is obtained by winding the wires in the same direction based on the obtained number of the wires.

The function realized by the addition operation of the output of the auxiliary winding is to output the same signal as the output of the main winding;

the first operational amplifier and the second operational amplifier are of the same type;

the difference processing after the integration of the main winding and other windings realizes a function of half the difference between the output voltage of the first operational amplifier and the output voltage of the second operational amplifier;

preferably, the method for acquiring the number of windings of the rogowski coil comprises the following steps:

based on the frequency of the measured signal and an external sampling resistor, acquiring the number of turns of each winding under the condition that the Rogowski coil is an external integrating circuit;

and acquiring the number of the windings by using the number of the windings and the diameter of the framework.

The specific principle is as follows:

assuming that the distance between a measured lead and the center of the coil is d, the radius of the coil wound by the winding is r, and mu is magnetic conductivity; the measured current is I, the number of turns of the coil is N, and then:

based on the biot savart law, the magnetic induction intensity can be calculated, and the method specifically comprises the following steps:

assuming that the wire is farther from the coil, the flux in a single winding can be calculated as follows:

then according to the law of electromagnetic induction, the single-winding induced voltage is:

the mutual inductance value M of the Rogowski coil single winding is defined by the mutual inductance

The self-inductance of the Rogowski coil is defined as NM:

to make the Rogowski coil an external integration circuit, it is necessary to satisfy omega L<<R_oWherein R is_oThe signal is an external sampling resistor, omega is 2 pi f, and f is a measured signal; in order to meet the above conditions, the number of turns N of each winding may be obtained;

in order to make the winding densely wound, the number of the windings is n, and then n is the maximum value of 2 × pi × d/Ns rounded downwards; d is the distance between the measured lead and the center of the Rogowski coil; s is the diameter of a single winding; n is the number of turns of each winding, and the N windings are wound in the same direction;

preferably, the condition that the rogowski coil is an outer integration circuit is: omega L<<R₀(ii) a Wherein, ω is 2 × pi × f, f is the measured signal; l is a single-winding inductance on the Rogowski coil; r₀Is externally connected with a sampling resistor.

Preferably, the number of windings is 2 × pi × d/Ns; d is the distance between the measured lead and the center of the Rogowski coil; s is the diameter of a single winding; n is the number of turns per winding.

Based on the current measuring method of the Rogowski coil, the invention provides a corresponding current measuring device, which comprises the following steps: the device comprises a first operational amplifier, a second operational amplifier, a Rogowski coil construction unit, a differential circuit and a calculation unit;

the input end of the differential circuit is connected with the output end of the first operational amplifier and the output end of the second operational amplifier;

when the operational amplifier is used, the first operational amplifier is connected with the output end of the Rogowski coil main winding to obtain the output voltage of the first operational amplifier;

when in use, the auxiliary windings of the Rogowski coil are added and then connected with a second operational amplifier to obtain the output voltage of the second operational amplifier;

the differential circuit is used for carrying out differential processing on the output voltage of the first operational amplifier and the output voltage of the second operational amplifier;

the calculation unit is used for calculating the number of windings of the Rogowski coil under the condition that the Rogowski coil is an external integration circuit; calculating output current according to the difference result;

the Rogowski coil construction unit is used for winding the windings in the same direction based on the obtained number of the windings to obtain the Rogowski coil, selecting one of the windings as a main winding, and using the rest windings as an auxiliary winding;

the output voltage of the main winding and the output voltage obtained after the addition operation of the auxiliary winding are respectively input to the first operational amplifier and the second operational amplifier in an out-of-phase mode.

Preferably, the calculation method of the number of windings of the rogowski coil is as follows:

based on the frequency of the measured signal and an external sampling resistor, acquiring the number of turns of each winding under the condition that the Rogowski coil is an external integrating circuit;

and acquiring the number of the windings by using the number of the windings and the diameter of the framework.

Preferably, the condition that the rogowski coil is an outer integration circuit is: omega L<<R₀(ii) a Wherein, ω is 2 × pi × f, f is the measured signal; l is a single-winding inductance on the Rogowski coil; r₀Is externally connected with a sampling resistor.

Preferably, the number of windings is 2 × pi × d/Ns; wherein d is the distance between the measured lead and the center of the Rogowski coil; s is the diameter of a single winding; n is the number of turns per winding.

The rogowski coil-based current measurement method disclosed herein may be stored in a computer-readable storage medium, on which a computer program is stored, which, when executed by a processor, may perform the steps of the current measurement method.

Examples

As shown in fig. 2, the rogowski coil in this embodiment is formed by winding 3 winding wires in the same direction, wherein one winding wire in fig. 2 is a main winding wire, and the other two winding wires are auxiliary winding wires;

FIG. 3 shows an integration circuit (first operational amplifier) corresponding to the main winding, in order to make the resistor R in the integration circuit₁The Rogowski coil is not influenced to be in an external integration state, and the resistor R is required to be arranged₀Much less than R₁；

Considering the offset voltage delta U of the operational amplifier, i.e. the inverting input terminal and the positive input terminal of the operational amplifier are higher than delta U, the output voltage of the integrating circuit corresponding to the main winding isWherein, U₁₂Outputting voltage for the main winding; c₁The main winding corresponds to a capacitor in the integrating circuit.

Fig. 4 shows an integration circuit (second operational amplifier) corresponding to the sub winding provided in the embodiment, and the output voltage of the integration circuit corresponding to the sub winding can be obtained from the addition circuit and the integration circuit corresponding to the sub winding:wherein, U_2'1'Is the inverse of the output voltage of one secondary winding; u shape_2”1”Is the opposite phase of the output voltage of the other secondary winding; wherein, U₁₂＝U_1’2’＝U_1”2”。

Fig. 5 is a differential circuit of the output of the main winding and the sub winding after the integration processing. As can be seen from fig. 5, the output voltage U of the differential circuit₃Is (U)₁-U₂) /2, i.e.Simplified to obtainTherefore, the influence of offset voltage is eliminated, and the waveform of the current to be measured can be accurately measured.

In conclusion, the Rogowski coil is obtained by winding the Rogowski coil in the same direction based on the winding number, the problem that the traditional framework is not adjustable is solved, and the stability of the Rogowski coil is enhanced. Meanwhile, the output end of the main winding is connected with a first operational amplifier, and after addition operation is carried out on the auxiliary windings, the main winding is connected with a second operational amplifier to obtain the output voltage of the second operational amplifier; calculating output current after performing difference processing on the output voltage of the first operational amplifier and the output voltage of the second operational amplifier; the integrating circuit corresponding to the Rogowski coil is completed, the influence of offset voltage of the operational amplifier is reduced by the integrating circuit, the accuracy of a final current measurement value is improved, and the primary side current waveform is convenient to restore.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.