CN111693753A - Novel direct current measuring device - Google Patents

Abstract

The invention discloses a novel direct current measuring device. It belongs to the technical field of DC current measurement technology of DC energy measurement technology, and the present invention is to solve the shortage of the existing DC current sensor in DC energy measurement. The phenomenon of "more metering" or "less metering" of electric energy, the present invention proposes a new type of DC current measurement device, which separates the DC current superimposed with the AC component, and outputs the DC component and the AC component respectively, which is the current of the DC energy meter. Acquisition provides a variety of options to further improve the accuracy of DC energy metering. A new type of DC current measuring device includes an electromagnet core for DC measurement, an electromagnet core for AC measurement, an input current measurement coil, an excitation current, a DC detection coil, a feedback coil, an AC detection coil, an amplifier circuit, an average value calculation circuit, Integrating circuit, power amplifier circuit, filter circuit, DC output and AC output.

Description

A Novel DC Current Measuring Device

technical field

The invention relates to the field of direct current measurement of direct current energy measurement technology, in particular to a novel direct current measurement device.

Background technique

In recent years, more and more DC transmission and distribution have been applied to the power grid. Different loads are connected in parallel on the DC transmission bus, such as powering motors or other AC devices through DC/AC, while AC loads often require reactive power. These reactive power demands through the DC/AC converter will cause an AC component to be superimposed on the input current of the DC side, which is generated by the reactive power demand of the AC side of the DCAC converter. In some occasions (such as subway locomotives), this part is superimposed on the DC side. The AC component is very large and the frequency is low, which is difficult to filter out by filtering means. With the wide application of the DC power grid, the DC energy meter will be used as an important basis for direct energy measurement. In the aforementioned phenomenon, the traditional DC sensor cannot decompose the DC component and the AC component of the current. In the case of a large AC component Under the current situation, the current signal collected by the traditional DC sensor is sent to the DC energy meter end, which will lead to the phenomenon of "over-metering" or "under-metering" of electric energy.

Traditional DC current sensors include shunts, Hall sensors, and magnetic modulation sensors. The current signals measured by shunts and Hall sensors contain both DC and AC components. In the measurement of DC energy meters, the AC components are used as effective The value is added to the DC component, and then the energy metering is performed. In the presence of reactive current in the load, it will lead to "multi-metering" of energy; the measurement result using the magnetic modulation DC sensor only contains the DC component, while the DC power of the DC grid The voltage is also superimposed with a certain AC component. The part of the AC component in the current signal that has the same frequency as the AC component in the voltage signal belongs to active power and must be measured. In this case, the magnetic modulation DC sensor measurement will lead to electric energy " under-measurement" phenomenon.

As an important instrument for metering and settlement in the future DC power grid, it is very necessary to improve the accuracy of power metering. According to the characteristics of the DC current in the DC power grid, the DC component and the AC component of the DC current are separated, and then the relevant processing is performed. An effective means to improve DC energy metering.

SUMMARY OF THE INVENTION

The invention is to solve the shortage of the existing DC current sensor in the measurement of DC electric energy. When a large AC component is superimposed on the DC current, the measurement result of the existing DC sensor may lead to the phenomenon of "over-metering" or "less-metering" of electric energy. The present invention proposes a new type of DC current measuring device, which decomposes the DC current into two parts, the DC component and the AC component, and provides multiple current options for accurate measurement of the DC energy meter in the DC power grid.

The above technical problems are solved by the following technical solutions:

A new type of DC current measuring device, including electromagnet core for DC measurement, electromagnet core for AC measurement, input current measurement coil, excitation current, DC detection coil, feedback coil, AC detection coil, amplifier circuit, average value calculation circuit , integrating circuit, power amplifier circuit, filter circuit, DC output and AC output. It is characterized in that the measured DC current is respectively wound on the electromagnet core for DC measurement and the electromagnet core for AC measurement through the input current measurement coil. The number of turns of the electromagnet core for measurement is larger than that of the electromagnet core for DC measurement, and its turns ratio is k; the excitation current generates an AC excitation current whose current frequency is greater than 2kHz, which is wound on the electromagnet core for DC measurement through a coil; DC The detection coil is wound on the electromagnet core for DC measurement; the feedback coil is respectively wound on the electromagnet core for DC measurement and the electromagnet core for AC measurement. The number of turns wound on the electromagnet core for AC measurement is greater than that of the electromagnet core for DC measurement, and its turns ratio is k; the AC detection coil is wound on the electromagnet core for AC measurement.

A new type of DC current measuring device is characterized in that the described DC current decomposition and measurement process superimposed with AC components are as follows:

The excitation current module generates an alternating current, and generates an alternating magnetic flux φ1 in the electromagnet core for DC measurement through the coil, so that the magnetic flux generated by the excitation current in the electromagnet core for DC measurement is close to the saturation point.

When the measured DC current is zero, the DC detection coil generates a symmetrical AC induced potential under the action of the AC excitation magnetic flux φ1, which is amplified by the amplifier circuit and then passed through the average value calculation circuit. The value is zero, so the induced potential generated by the DC detection coil is output to zero after the average calculation circuit, the integration circuit and the DC output.

When the measured DC current is not zero, it generates a DC magnetic flux φ2 in the DC measurement electromagnet core and the AC measurement electromagnet core respectively through the input circuit measurement coil, and because the DC measurement electromagnet core acts on the excitation current The AC magnetic flux φ1 generated at the bottom is already at the saturation point, and the combined action of the two magnetic fluxes will make the magnetic flux in the electromagnet core for DC measurement enter the nonlinear saturation region. If the positive direction of the magnetic flux is the same, the upper half wave of the synthesized magnetic flux enters nonlinear saturation. At this time, the DC detection coil produces asymmetrically distorted AC induced potential under the action of the AC/DC synthesized magnetic flux, which shows that the upper half wave is smaller than the lower one. Half-wave, the induced potential outputs the average value after passing through the amplifier circuit and the average value calculation circuit. After passing through the integrating circuit, and then passing through the power amplifier circuit, the DC magnetic flux φ3 opposite to the direction of the DC magnetic flux φ2 is generated through the feedback coil. When φ2 is not equal to When φ3, the DC detection coil still generates asymmetrical AC induced potential under the action of the synthetic magnetic flux, and the output is not zero after the average value calculation circuit. The current continues to increase, and the DC magnetic flux φ3 also continues to increase. When φ2 is equal to φ3, the DC magnetic flux in the electromagnet core for DC measurement is canceled, and the DC detection coil produces a symmetrical AC induction under the action of the AC magnetic flux φ1. At this time, the output of the average value calculation circuit is 0, the output of the integration circuit is no longer increased, and the DC output module outputs the measured DC current to realize the DC current measurement.

When the measured DC current does not contain AC components, the DC magnetic flux φ2 in the electromagnet core for AC measurement and the DC magnetic flux φ3 generated by the feedback coil cancel each other out, the AC detection coil has no induced electromotive force, and the output is zero.

When the measured DC current contains AC components, under the action of the average value calculation circuit, the integration circuit, the power amplifier circuit and the feedback coil, the DC magnetic flux φ2 in the electromagnet core for AC measurement and the DC magnetic flux φ3 generated by the feedback coil They cancel each other out. At this time, the AC component of the current to be measured generates an alternating magnetic flux φ4 in the electromagnet core for AC measurement. Since the input current measurement coil has more turns in the electromagnet core for AC measurement, the AC component generates an alternating magnetic flux φ4. The effect of magnetomotive force is obvious. At this time, the AC detection coil generates induced electromotive force. After filtering and AC output, the measurement of the AC component of the measured current is realized.

The present invention can achieve the following effects:

The invention separates the DC current superimposed with the AC component, outputs the DC component and the AC component respectively, provides multiple options for the current collection of the DC electric energy meter, and further improves the accuracy of the DC electric energy measurement.

Description of drawings

FIG. 1 is a schematic block diagram of a novel direct current measuring device of the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

An embodiment, a new type of DC current measurement device, as shown in FIG. 1, includes an electromagnet core 1 for DC measurement, an electromagnet core 2 for AC measurement, an input current measurement coil 3, an excitation current 4, a DC detection coil 5, Feedback coil 6 , AC detection coil 7 , amplifier circuit module 8 , average value calculation circuit module 9 , integration circuit module 10 , power amplifier circuit module 11 , filter circuit module 12 , DC output module 13 and AC output module 14 . The measured DC current is respectively wound on the electromagnet core 1 for DC measurement and the electromagnet core 2 for AC measurement through the input current measurement coil 3, and the current directions of the two iron cores are the same, and the number of turns is different, The number of turns wound on the electromagnet core 2 for AC measurement is greater than that of the electromagnet core 1 for DC measurement, and its turns ratio is k; the excitation current 4 generates an AC excitation current, and its current frequency is greater than 2kHz, which is wound through the coil in the DC measurement. On the electromagnet core 1; the DC detection coil 5 is wound on the electromagnet core 1 for DC measurement; the feedback coil 6 is respectively wound on the electromagnet core 1 for DC measurement and the electromagnet core 2 for AC measurement, and is wound on the two The current direction of each iron core is the same, and the number of turns is different. The number of turns wound on the electromagnet core 2 for AC measurement is greater than that of the electromagnet core 1 for DC measurement, and its turns ratio is k; the AC detection coil 7 is wound around the electromagnetic core for AC measurement. iron core 2.

A new type of DC current measuring device is characterized in that the described DC current decomposition and measurement process superimposed with AC components are as follows:

The excitation current module 4 generates an alternating current, and generates an alternating magnetic flux φ1 in the electromagnet core 1 for DC measurement through the coil, so that the magnetic flux generated by the excitation current in the electromagnet core 1 for DC measurement is close to the saturation point.

When the measured DC current is zero, the DC detection coil 5 generates a symmetrical AC induced potential under the action of the AC excitation magnetic flux φ1, which is amplified by the amplifier circuit 8 and then passed through the average value calculation circuit 9. The average value in the cycle is zero, so the induced potential generated by the DC detection coil 5 is output to zero after passing through the average value calculation circuit 9 , the integrating circuit 10 and the DC output 13 .

When the measured DC current is not zero, the input circuit measuring coil 3 generates a DC magnetic flux φ2 in the electromagnet core 1 for DC measurement and the electromagnet core 2 for AC measurement, and because the electromagnet core 1 for DC measurement is in The AC magnetic flux φ1 generated under the action of the excitation current 4 is already at the saturation point, and the combined action of the two magnetic fluxes will make the magnetic flux in the electromagnet core 1 for DC measurement enter the nonlinear saturation region. The positive direction of the AC magnetic flux generated by the current is the same, then the upper half-wave of the synthesized magnetic flux enters nonlinear saturation. At this time, the DC detection coil 5 generates an asymmetric distorted AC induced potential under the action of the AC/DC synthesized magnetic flux, which shows In order that the upper half wave is smaller than the lower half wave, the induced potential is outputted by the amplifying circuit 8 and the average value calculating circuit 9, and the average value is outputted by the integrating circuit 10 and then the power amplifying circuit 11. In contrast to the DC magnetic flux φ3, when φ2 is not equal to φ3, the DC detection coil 5 still generates an asymmetrical AC induced potential under the action of the combined magnetic flux, and the output is not zero after the average value calculation circuit 9, in the integrating circuit 10 Under the action of , the integral output continues to increase, so that the feedback coil current continues to increase, and the DC magnetic flux φ3 also continues to increase until φ2 is equal to φ3, the DC magnetic flux in the electromagnet core 1 for DC measurement is cancelled, and the DC The detection coil 5 generates a symmetrical AC induced potential under the action of the AC magnetic flux φ1. At this time, the output of the average calculation circuit 9 is 0, the output of the integrating circuit 10 is no longer increased, and the DC output 13 outputs the measured DC current, which realizes the DC current measurement.

When the measured DC current does not contain AC components, the DC magnetic flux φ2 in the AC measuring electromagnet core 2 and the DC magnetic flux φ3 generated by the feedback coil cancel each other out, and the output of the AC detection coil 7 is zero.

When the measured DC current contains AC components, under the action of the average value calculation circuit 9, the integrating circuit 10, the power amplifier circuit 11 and the feedback coil 6, the DC magnetic flux φ2 in the electromagnet core 2 for AC measurement and the feedback coil generate The DC magnetic flux φ3 cancels each other out. At this time, the AC component of the current to be measured will generate an alternating magnetic flux φ4 in the electromagnet core 2 for AC measurement. If the number is more, the effect of magnetomotive force generated by the AC component is obvious. At this time, the AC detection coil 7 generates an induced electromotive force, and the AC component of the measured current is measured through the filter circuit 12 and the AC output 14 .

Claims (2)

1. A novel direct current measuring device comprises an electromagnet core for direct current measurement, an electromagnet core for alternating current measurement, an input current measuring coil, an excitation current, a direct current detecting coil, a feedback coil, an alternating current detecting coil, an amplifying circuit, an average value calculating circuit, an integrating circuit, a power amplifying circuit, a filter circuit, direct current output and alternating current output. The device is characterized in that the measured direct current is respectively wound on a direct current measuring electromagnet core and an alternating current measuring electromagnet core through an input current measuring coil, the current directions of the two iron cores are the same, the turns are different, the number of turns of the wound direct current measuring electromagnet core is greater than that of the direct current measuring electromagnet core, and the turn ratio is k; the exciting current generates alternating exciting current, the current frequency of the alternating exciting current is more than 2kHz, and the alternating exciting current is wound on the electromagnet core for direct current measurement through a coil; the direct current detection coil is wound on the electromagnet core for direct current measurement; the feedback coil is respectively wound on the electromagnet core for direct current measurement and the electromagnet core for alternating current measurement, the current directions of the two iron cores are the same, the turns are different, the number of turns of the feedback coil wound on the electromagnet core for alternating current measurement is larger than that of the electromagnet core for direct current measurement, and the turn ratio is k; the alternating current detection coil is wound on the electromagnet core for alternating current measurement.

2. A novel dc current measuring device suitable for use in claim 1, wherein the dc current with the superimposed ac component is decomposed and measured as follows:

the exciting current module generates alternating current, and alternating current magnetic flux phi 1 is generated in the direct current measuring electromagnet core through the coil, so that the magnetic flux generated by the exciting current in the direct current measuring electromagnet core is close to a saturation point;

when the detected direct current is zero, the direct current detection coil generates symmetrical alternating current induced potential under the action of the alternating current excitation magnetic flux phi 1, the symmetrical alternating current induced potential is amplified by the amplifying circuit and then passes through the average value calculating circuit, and the induced potential is symmetrical up and down and the average value in the period is zero, so that the induced potential generated by the direct current detection coil is output to be zero after passing through the average value calculating circuit, the integrating circuit and the direct current output;

when the direct current to be measured is not zero, the direct current phi 2 is respectively generated in the electromagnet core for direct current measurement and the electromagnet core for alternating current measurement through the measuring coil of the input circuit, and the alternating current phi 1 generated by the electromagnet core for direct current measurement under the action of the exciting current is already at a saturation point, the magnetic flux in the electromagnet core for direct current measurement enters a nonlinear saturation area under the combined action of the two magnetic fluxes, the direction of the direct current is set to be the same as the positive direction of the alternating current generated by the exciting current, the upper half wave of the synthesized magnetic flux enters nonlinear saturation, at the moment, the direct current detecting coil generates asymmetric distorted alternating current induced potential under the action of the synthesized magnetic flux, the distorted alternating current induced potential is represented as that the upper half wave is smaller than the lower half wave, the induced potential outputs an average value after passing through the amplifying circuit and the average value calculating circuit, then passes through the integrating circuit, and then the direct current phi 3 with the direction opposite to the direct current, when phi 2 is not equal to phi 3, the direct current detection coil still generates asymmetric alternating current induced potential under the action of the synthesized magnetic flux, the output is not zero after passing through the average value calculation circuit, the integral output is continuously increased under the action of the integral circuit, so that the current of the feedback coil is continuously increased, the direct current magnetic flux phi 3 is also continuously increased, until phi 2 is equal to phi 3, the direct current magnetic flux in the electromagnet core for direct current measurement is counteracted, the direct current detection coil generates symmetric alternating current induced potential under the action of the alternating current magnetic flux phi 1, at the moment, the output is 0 through the average value calculation circuit, the output of the integral circuit is not increased, the direct current output module outputs the measured direct current, and the direct current measurement is realized;

when the measured direct current does not contain an alternating current component, the direct current magnetic flux phi 2 in the electromagnet core for alternating current measurement and the direct current magnetic flux phi 3 generated by the feedback coil are mutually offset, the alternating current detection coil does not induce electromotive force, and the output is zero;

when the measured direct current contains alternating current components, under the action of the average value calculating circuit, the integrating circuit, the power amplifying circuit and the feedback coil, direct current magnetic flux phi 2 in the electromagnet core for alternating current measurement and direct current magnetic flux phi 3 generated by the feedback coil are mutually counteracted, at the moment, alternating magnetic flux phi 4 is generated in the electromagnet core for alternating current measurement by alternating current components of the measured current, as the number of turns of the input current measuring coil in the electromagnet core for alternating current measurement is more, the magnetomotive force generated by the alternating current components has obvious action, at the moment, the alternating current detecting coil generates induced electromotive force, and the measurement of the alternating current components of the measured current is realized through filtering and alternating current output.

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