CN114740245B - Excitation-magnetization-detection three-stage differential weak current measuring device - Google Patents
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Abstract
The invention relates to an excitation-magnetization-detection three-level differential weak current measuring device, which comprises: a differential magnetization unit, a differential excitation unit and a differential detection unit; the alternating square wave voltage source and the current measuring device are respectively in four working states of positive, negative, positive, negative and negative, and the output current value of the weak current measuring device is obtained through calculation according to four current measured values of the current measuring device in the four working states; on the basis of a traditional single-stage differential structure, a differential excitation and differential detection structure is introduced, so that the influence of micro-asymmetry of an excitation power supply and a detection loop on a sensor is greatly weakened, the resolution and accuracy of weak current detection are further improved, a foundation is laid for advanced application of a smart grid, and the safe and stable operation of the system is guaranteed.
Description
Technical Field
The invention relates to the technical field of electrical measurement, in particular to an excitation-magnetization-detection three-level differential weak current measuring device.
Background
The current is one of the information quantity of the power grid electric quantity detection, and the realization of the comprehensive and accurate measurement plays a key role in the construction of the whole intelligent power grid system. The electric energy can be allocated at any time through monitoring and measuring the power grid, and faults and potential safety hazards can be found timely.
The current measuring device plays an important role as important power equipment for detecting the magnitude and direction of current in real time in the fields of smart grids, new energy automobiles, aerospace and the like. In recent years, with the introduction of smart grid concepts, higher demands have been made on the accuracy, measurement range, and the like of current measurement devices.
The current measuring device mainly comprises a Hall current sensor, a reluctance type current sensor and a magnetic modulation type current sensor. The Hall sensor has low resolution and large temperature drift; the reluctance type sensor has high sensitivity and good linearity, but is easily interfered by noise; the magnetic modulation type current sensor has the advantages of low noise and high stability, and is widely applied to the field of weak current detection.
There are two current types of magnetic modulation current sensors, i.e., open loop type and closed loop type. The measurement error of the feedback loop of the closed loop type sensor can cause the closed loop type sensor to lose the advantage of high precision in a weak current detection scene. Therefore, the open-loop sensor is more suitable for measuring weak current, and students at home and abroad carry out certain research on the optimal design and the practical application of the open-loop magnetic modulator.
The traditional open-loop magnetic modulation type current sensor usually adopts a single-stage differential structure and is composed of two main iron cores with the same structure size and basically consistent magnetic characteristics. The two iron cores are respectively wound with excitation windings with strictly consistent turns, and the two excitation windings are reversely connected in series, so that the bias magnetic flux generated by the current to be measured is consistent with the magnetic flux generated by the excitation winding of one iron core in direction, and is just opposite to the magnetic flux generated by the excitation winding of the other iron core. Therefore, the detection sensitivity of the single-stage differential magnetic modulation type sensor is enhanced by 2 times, and the anti-interference performance is greatly improved.
However, when the magnetic modulation type current sensor measures weak current, the measurement accuracy of the sensor is affected by the micro-asymmetry of the excitation power supply and the detection loop of the magnetic modulation type current sensor, and the further improvement of the measurement resolution is limited. Therefore, a novel weak current measuring method and device are urgently needed, the resolution and accuracy of current detection are further improved, and a foundation is laid for safe and stable operation of the smart grid.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides an excitation-magnetization-detection three-level differential weak current measuring device, which introduces a differential excitation and differential detection structure on the basis of a traditional single-level differential structure, controls a differential excitation unit to control and switch the working states of positive excitation and negative excitation to form a first-level differential; excitation windings of the two annular magnetic cores are reversely connected in series to form a second-stage differential; controlling the differential detection unit to switch the working states of positive detection and negative detection to form a third-stage differential; the influence of the micro-asymmetry of the excitation power supply and the detection loop on the sensor is greatly weakened, the resolution and the accuracy of weak current detection are further improved, a foundation is laid for advanced application of the smart grid, and the safe and stable operation of the system is guaranteed.
According to a first aspect of the present invention, there is provided an excitation-magnetization-detection three-stage differential weak current measuring device comprising: a differential magnetization unit, a differential excitation unit and a differential detection unit;
the differential magnetizing unit comprises an annular magnetic core C 1 And a ring shapeMagnetic core C 2 Said toroidal core C 1 Is provided with an excitation winding W e1 And a detection winding W D1 Said toroidal core C 2 Is provided with an excitation winding W e2 And a detection winding W D2 Said excitation winding W e1 And an excitation winding W e2 Reverse series connection, the detection winding W D1 And a detection winding W D2 Are connected in series;
the differential excitation unit comprises an alternating square wave voltage source, and two ends of the alternating square wave voltage source are respectively connected with the excitation winding W e1 And an excitation winding W e2 Is connected with one end of the connecting rod;
the differential detection unit comprises current measuring devices respectively connected with the detection winding W D1 And a detection winding W D2 Is connected with one end of the connecting rod;
setting the positive pole of the alternating square wave voltage source and the exciting winding W e1 Connecting the negative pole with the excitation winding W e2 When the differential magnetization unit is connected, the differential magnetization unit is in a positive working state; the positive electrode of the current measuring device and the detection winding W D1 Connecting the negative pole with the detection winding W D2 When the differential detection unit is connected, the differential detection unit is in a positive working state;
and enabling the alternating square wave voltage source and the current measuring device to be respectively in four working states of positive and positive, positive and negative, negative and positive and negative, and calculating the output current value of the weak current measuring device according to four current measured values of the current measuring device in the four working states.
On the basis of the technical scheme, the invention can be improved as follows.
Optionally, the weak current measuring apparatus further includes a differential control module; the differential excitation unit further comprises differential switches S 11 、S 21 、S 12 And S 22 (ii) a The differential detection unit further comprises a differential switch S 33 、S 34 、S 43 And S 44 ；
The differential switch S 11 、S 21 、S 12 And S 22 The positive electrode and the negative electrode of the alternating square wave voltage source are respectively arranged on the excitation winding W e1 And the excitation winding W e2 The connecting branch of (2);
the differential switch S 33 、S 34 、S 43 And S 44 A positive electrode and a negative electrode respectively arranged on the current measuring device and the detection winding W D1 And the detection winding W D2 The connecting branch of (1);
the differential control module controls each differential switch S 11 、S 21 、S 12 、S 22 、S 33 、S 34 、S 43 And S 44 The alternating square wave voltage source and the current measuring device are in a positive working state or a negative working state.
Optionally, after completing the current measurement in the positive working state, the differential detection unit sends a switching signal to the differential control module, and the differential control module modifies the working states of the alternating square-wave voltage source and the current measurement device into the positive and negative working states after receiving the switching signal;
after the current measurement of the positive working state and the negative working state is finished, the differential detection unit sends a switching signal to the differential control module, and the differential control module modifies the working states of the alternating square wave voltage source and the current measurement device into a negative working state and a positive working state after receiving the switching signal;
after finishing the current measurement in the negative and positive working states, the differential detection unit sends a switching signal to the differential control module, and the differential control module modifies the working states of the alternating square wave voltage source and the current measurement device into the negative and negative working states after receiving the switching signal;
and the differential detection unit sends a switching signal to the differential control module after finishing the current measurement in a negative working state, and the differential control module modifies the working states of the alternating square wave voltage source and the current measurement device into a positive working state after receiving the switching signal.
Optionally, the weak current measuring apparatus further includes an output module;
the current measuring device outputs the measured current values under various working states to the output module, and the output module calculates the output current value to output.
Optionally, the current measuring device includes an AD chip and a microprocessor thereof; the AD chip and the microprocessor thereof collect n second output voltage signals OUT of the differential magnetization unit 1 For the output voltage signal OUT 1 Carrying out analog-to-digital conversion and data demodulation to obtain current measurement values in each working state; and n is the set sampling time.
Optionally, the current measuring device periodically and cyclically acquires current values in four working states; the period is 4n seconds;
and calculating each period to obtain the output current value and then outputting the output current value.
Optionally, a fourier analysis algorithm is used to correct the output voltage signal OUT 1 Carrying OUT data demodulation to obtain an output voltage signal OUT in the ith working state i After the second harmonic component, dividing the second harmonic component by a proportionality coefficient K to obtain the current measurement value I in the ith working state mi 。
Optionally, the output current value
The calculation formula of (2) is as follows:
wherein the content of the first and second substances,
、
、
and
and the current measuring values respectively represent the current measuring values containing phase information when the alternating square wave voltage source and the current measuring device are respectively in four working states of positive, negative, positive and negative.
Optionally, the ring-shaped magnetic core C 1 And a toroidal core C 2 The dimension materials are the same;
the excitation winding W e1 And an excitation winding W e2 Are the same.
The excitation-magnetization-detection three-level differential weak current measuring device provided by the embodiment of the invention introduces a differential excitation and differential detection structure on the basis of a traditional single-level differential structure, a differential excitation unit consists of an alternating square wave voltage source and 4 differential switches, the alternating square wave voltage source is usually an alternating voltage source, so that a differential magnetic ring unit is in a saturated state, and the 4 differential switches are used for controlling and switching a positive excitation working state and a negative excitation working state to form a first-level differential; excitation windings of the two annular magnetic cores are connected in series in an opposite direction to form a second-stage differential; the differential detection unit consists of a current measuring device and 4 differential switches, the current measuring device consists of an AD chip and a microprocessor thereof, the output voltage of the differential magnetization unit is subjected to analog-to-digital conversion and data demodulation, and the 4 differential switches are used for controlling and switching the working states of positive detection and negative detection to form third-stage differential; the influence of the micro-asymmetry of the excitation power supply and the detection loop on the sensor is greatly weakened, the resolution and the accuracy of the weak current detection are further improved, a foundation is laid for the advanced application of the smart grid, and the safe and stable operation of the system is guaranteed; the current measuring device is formed by the AD chip and the microprocessor thereof, the sampling precision is high, the extra error introduced by a detection loop is less, the working stability is good, and the foundation is laid for high-accuracy demodulation.
Drawings
Fig. 1 is a schematic structural diagram of an embodiment of an excitation-magnetization-detection three-level differential weak current measurement device provided by the present invention;
fig. 2 is a flowchart of a measuring method of an excitation-magnetization-detection three-stage differential weak current measuring apparatus according to an embodiment of the present invention;
in the drawings, the reference numbers indicate the following list of parts:
1 is an alternating square wave voltage source, and 2 is a differential switch S 11 3 is a differential switch S 21 And 4 is a differential switch S 12 5 is a differential switch S 22 6 is an excitation winding W e1 And 7 is an excitation winding W e2 8 is a ring-shaped magnetic core C 1 9 is a ring-shaped magnetic core C 2 10 is a detection winding W D1 And a detection winding W D2 11 is a differential switch S 33 12 is a differential switch S 34 13 is a differential switch S 43 14 is a differential switch S 44 15 is a current measuring device, 16 is an output module, and 17 is a differential control module.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
The excitation-magnetization-detection three-level differential weak current measuring device provided by the invention aims to further improve the resolution and accuracy of weak current detection, lay a foundation for advanced application of a smart grid and ensure safe and stable operation of a system. Fig. 1 is a schematic structural diagram of an embodiment of an excitation-magnetization-detection three-stage differential weak current measuring apparatus according to the present invention, as shown in fig. 1, the weak current measuring apparatus includes: the device comprises a differential magnetization unit, a differential excitation unit and a differential detection unit.
The differential magnetizing unit comprises a ring-shaped magnetic core C 1 And a toroidal core C 2 Annular magnetic core C 1 Is provided with an excitation winding W e1 And a detection winding W D1 Annular magnetic core C 2 Is provided with an excitation winding W e2 And a detection winding W D2 Excitation winding W e1 And an excitation winding W e2 Reverse series connection, detecting winding W D1 And a detection winding W D2 Are connected in series.
The differential excitation unit comprises an alternating square wave voltage source, and two ends of the alternating square wave voltage source are respectively connected with the excitation winding W e1 And an excitation winding W e2 Is connected at one end.
The differential detection unit comprises a current measuring device respectively connected with the detection winding W D1 And a detection winding W D2 Is connected at one end.
Setting the positive pole of the alternating square wave voltage source and the excitation winding W e1 Connecting the negative pole to the excitation winding W e2 When the differential magnetization unit is connected, the differential magnetization unit is in a positive working state; alternating square wave voltage source anode and excitation winding W e2 Connecting the negative pole to the excitation winding W e1 When the differential magnetization unit is connected, the differential magnetization unit is in a negative working state; positive pole and detection winding W of current measuring device D1 Connection, negative pole and detection winding W D2 When the differential detection unit is connected, the differential detection unit is in a positive working state; positive pole and detection winding W of current measuring device D2 Connection, negative pole and detection winding W D1 When connected, the differential detection unit is in a negative working state.
The alternating square wave voltage source and the current measuring device are respectively in four working states of positive, negative, positive, negative and negative, and the output current value of the weak current measuring device is obtained by calculation according to four current measurement values of the current measuring device in the four working states.
The invention provides an excitation-magnetization-detection three-level differential weak current measuring device, which introduces a differential excitation and differential detection structure on the basis of a traditional single-level differential structure, controls a differential excitation unit to control and switch the working states of positive excitation and negative excitation to form a first-level differential; excitation windings of the two annular magnetic cores are connected in series in an opposite direction to form a second-stage differential; controlling a differential detection unit to switch between a positive detection working state and a negative detection working state to form a third-stage differential motion; the influence of the micro asymmetry of the excitation power supply and the detection loop on the sensor is greatly weakened, the resolution and the accuracy of weak current detection are further improved, a foundation is laid for advanced application of a smart grid, and the safe and stable operation of the system is guaranteed.
Example 1
Embodiment 1 of the present invention is an embodiment of an excitation-magnetization-detection three-stage differential weak current measuring apparatus provided by the present invention, and as shown in fig. 2, a flowchart of a measuring method of the excitation-magnetization-detection three-stage differential weak current measuring apparatus provided by the embodiment of the present invention is shown, and as can be seen from fig. 1 and fig. 2, the embodiment of the weak current measuring apparatus includes: the device comprises a differential magnetization unit, a differential excitation unit, a differential detection unit, a differential control module and an output module.
The differential magnetizing unit comprises an annular magnetic core C 1 And a toroidal core C 2 Toroidal core C 1 Is provided with an excitation winding W e1 And a detection winding W D1 Toroidal core C 2 Is provided with an excitation winding W e2 And a detection winding W D2 Excitation winding W e1 And an excitation winding W e2 Reverse series connection, detecting winding W D1 And a detection winding W D2 Are connected in series.
The differential excitation unit comprises an alternating square wave voltage source, and two ends of the alternating square wave voltage source are respectively connected with the excitation winding W e1 And an excitation winding W e2 Is connected at one end.
The differential detection unit comprises a current measuring device respectively connected with the detection winding W D1 And a detection winding W D2 Is connected at one end.
Setting the positive pole of the alternating square wave voltage source and the excitation winding W e1 Connection, negative pole and excitation winding W e2 When the differential magnetization unit is connected, the differential magnetization unit is in a positive working state; alternating square wave voltage source anode and excitation winding W e2 Connecting the negative pole to the excitation winding W e1 When the differential magnetization unit is connected, the differential magnetization unit is in a negative working state; positive pole and detection winding W of current measuring device D1 Connection, negative pole and detection winding W D2 When the differential detection unit is connected, the differential detection unit is in a positive working state; positive pole and detection winding W of current measuring device D2 Connection, negative pole and detection winding W D1 When connected, the differential detection unit is in a negative working state.
The alternating square wave voltage source and the current measuring device are respectively in four working states of positive, negative, positive, negative and negative, and the output current value of the weak current measuring device is obtained by calculation according to four current measurement values of the current measuring device in the four working states.
In a possible embodiment mode, the differential excitation unit further comprises respective differential switches S 11 、S 21 、S 12 And S 22 (ii) a The differential detection unit further comprises a differential switch S 33 、S 34 、S 43 And S 44 。
Differential switch S 11 、S 21 、S 12 And S 22 The positive pole and the negative pole of the alternating square wave voltage source are respectively arranged with the exciting winding W e1 And an excitation winding W e2 Is connected to the branch.
Differential switch S 33 、S 34 、S 43 And S 44 A positive electrode and a negative electrode respectively arranged on the current measuring device and the detection winding W D1 And a detection winding W D2 Is connected to the branch.
The differential control module controls each differential switch S 11 、S 21 、S 12 、S 22 、S 33 、S 34 、S 43 And S 44 The alternating square wave voltage source and the current measuring device are in a positive working state or a negative working state.
In a possible embodiment, after completing the current measurement in the positive working state, the differential detection unit sends a switching signal to the differential control module, and the differential control module receives the switching signal and modifies the working states of the alternating square-wave voltage source and the current measurement device into the positive working state and the negative working state.
After finishing the current measurement of the positive and negative working states, the differential detection unit sends a switching signal to the differential control module, and the differential control module modifies the working states of the alternating square wave voltage source and the current measurement device into a negative and positive working state after receiving the switching signal.
After finishing the current measurement in the negative and positive working states, the differential detection unit sends a switching signal to the differential control module, and the differential control module modifies the working states of the alternating square wave voltage source and the current measurement device into the negative and negative working states after receiving the switching signal.
After finishing the current measurement in the negative working state, the differential detection unit sends a switching signal to the differential control module, and the differential control module modifies the working states of the alternating square wave voltage source and the current measurement device into the positive working state after receiving the switching signal.
In specific implementation, in the embodiment shown in fig. 1, the differential control module outputs a positive control signal to enable the differential switch S 11 、S 21 、S 33 And S 44 And closing the switch, wherein the differential excitation unit and the differential detection unit are in positive working states.
After receiving the switching signal, the differential control module outputs a positive and negative control signal to make the differential switch S 11 、S 21 、S 34 And S 43 And when the differential excitation unit is closed, the differential excitation unit is switched to a positive working state, and the differential detection unit is switched to a negative working state.
After receiving the switching signal, the differential control module outputs a negative and positive control signal to make the differential switch S 21 、S 12 、S 33 And S 44 And when the differential excitation unit is closed, the differential excitation unit is switched to a negative working state, and the differential detection unit is switched to a positive working state.
After receiving the switching signal, the differential control module outputs a negative control signal to make the differential switch S 21 、S 12 、S 34 And S 43 And when the differential excitation unit and the differential detection unit are closed, the differential excitation unit and the differential detection unit are switched to a negative working state.
After receiving the switching signal of the differential detection unit, the differential control module outputs a control signal to the 8 differential switches each time, switches the closing state of the differential switches, and the control signal is sequentially circulated according to the sequence of positive, negative, and negative.
In a possible embodiment mode, the weak current measuring apparatus further includes an output module.
The current measuring device outputs the measured current values under various working states to the output module, and the output module calculates the output current values to output.
In a possible embodiment mode, the current measuring device comprises an AD chip and a microprocessor thereof; AD chip and microprocessor thereof for acquiring n second output voltage signal OUT of differential magnetization unit 1 To the output voltage signal OUT 1 Carrying out analog-to-digital conversion and data demodulation to obtain current measurement values in each working state; and n is the set sampling time. Preferably, in this embodiment, the sampling time n =1 according to the requirement of data demodulation precision.
In a possible embodiment mode, the current measuring device periodically and circularly acquires current values in four working states; the period is 4n seconds.
And calculating in each period to obtain an output current value and then outputting.
In one possible embodiment, the output voltage signal OUT is analyzed by a Fourier analysis algorithm 1 Carrying OUT data demodulation to obtain an output voltage signal OUT in the ith working state i After the second harmonic component, dividing the second harmonic component by a proportionality coefficient K to obtain a current measured value I in the ith working state mi . The expression is as follows:
wherein i =1, 2, 3 or 4. Preferably, the specific value of the proportionality coefficient K is related to the excitation source voltage and the magnetic core material. Preferably, in the present embodiment, the excitation source voltage is 36V, and the magnetic core material is permalloy, so that the proportionality coefficient K =3.16.
In a possible embodiment mode, the current value is output
The calculation formula of (c) is:
wherein, the first and the second end of the pipe are connected with each other,
、
、
and
respectively representing the current measurement values containing phase information when the alternating square wave voltage source and the current measurement device are respectively in four working states of positive, negative, positive, negative and negative.
In a possible embodiment mode, the annular magnetic core C 1 And a toroidal core C 2 Are the same in size material.
Excitation winding W e1 And an excitation winding W e2 Are the same.
With reference to fig. 2, in a possible embodiment, the differential excitation unit is composed of an alternating square wave voltage source 1 and 4 differential switches 2-5, the alternating square wave voltage source is an alternating square wave voltage source, the voltage amplitude of the alternating square wave voltage source can be 36V, the excitation frequency is 155Hz, so that the differential magnetic ring unit is in a saturated state, and the 4 differential switches 2-5 control to switch a "positive" excitation working state and a "negative" excitation working state, so as to form a first-stage differential, and weaken a measurement error introduced by asymmetry of the square wave voltage source.
The differential magnetization unit consists of permalloy annular magnetic cores 8 and annular magnetic cores 9 which are basically identical, 100 turns of excitation windings 6 and 7 are wound on each magnetic core respectively, the excitation winding 6 and the excitation winding 7 are reversely connected in series to form a second-stage differential, the sensitivity of the current measuring device is enhanced, 200 turns of detection windings are wound on the two magnetic cores, and the output voltage is transmitted to the differential detection unit.
The differential detection unit consists of a current measuring device 15 and 4 differential switches 11-14, the current measuring device 15 consists of an AD chip and a microprocessor, the output voltage of the differential magnetization unit is subjected to analog-to-digital conversion and data demodulation, and the 4 differential switches 11-14 control and switch the working states of positive detection and negative detection to form third-stage differential, so that the measurement error introduced by the detection loop is weakened.
After receiving the switching signal of the differential detection unit, the differential control module 17 outputs a control signal to 8 differential switches (2-5, 11-14) to switch the closing state of the differential switches, and the control signal circulates in sequence of positive-negative-positive-negative.
The excitation-magnetization-detection three-stage differential weak current measuring method and device can greatly weaken the influence of the micro asymmetry of an excitation power supply and a detection loop on a sensor, and further improve the resolution and accuracy of weak current detection.
Example 2
Embodiment 2 provided in the present invention is an embodiment of a measurement method of an excitation-magnetization-detection three-stage differential weak current measurement apparatus provided in the embodiment of the present invention, and as can be seen from fig. 1 and fig. 2, the measurement method of the excitation-magnetization-detection three-stage differential weak current measurement apparatus provided in the embodiment of the present invention includes:
s1, the differential control module outputs a positive control signal to enable the differential switch S 11 、S 21 、S 33 And S 44 When the circuit is closed, the differential excitation unit and the differential detection unit are both in a positive working state.
S2, the current measuring device collects n second output voltage signals OUT of the differential magnetization unit 1 And demodulating the data to obtain the current measurement value in the positive state
。
And S3, the differential detection unit transmits the current measurement value to the output module and outputs a switching signal to the differential control module.
S4, after receiving the switching signal, the differential control module outputs a positive and negative control signal to enable the differential switch S 11 、S 21 、S 34 And S 43 When the differential excitation unit is closed, the differential excitation unit is switched to a positive working state, and the differential detection unit is switchedWhen the current reaches the negative working state, the steps S2 and S3 are repeated to obtain the current measurement value under the positive and negative working states
。
S5, after receiving the switching signal, the differential control module outputs a negative and positive control signal to enable the differential switch S 21 、S 12 、S 33 And S 44 Closing, switching the differential excitation unit to a negative working state, switching the differential detection unit to a positive working state, repeating the steps S2 and S3 to obtain a current measurement value in the negative and positive states
。
S6, after receiving the switching signal, the differential control module outputs a negative control signal to enable the differential switch S 21 、S 12 、S 34 And S 43 When the differential excitation unit and the differential detection unit are closed, the differential excitation unit and the differential detection unit are switched to a negative working state, the steps S2 and S3 are repeated to obtain a current measurement value in the negative working state
。
S7, the output module analyzes and processes the current measurement values of the 4 states and outputs the current measurement values
。
S8, repeating the steps S1-S7, sequentially outputting a positive-negative positive-negative control signal by the differential control module, and outputting 1 accurate current measurement value every 4n seconds
。
It should be understood that, the excitation-magnetization-detection three-stage differential weak current measuring method provided by the present invention corresponds to the excitation-magnetization-detection three-stage differential weak current measuring device provided in the foregoing embodiments, and the technical features of the excitation-magnetization-detection three-stage differential weak current measuring method can refer to the technical features of the excitation-magnetization-detection three-stage differential weak current measuring device, which are not described herein again.
The excitation-magnetization-detection three-level differential weak current measuring device provided by the embodiment of the invention introduces a differential excitation and differential detection structure on the basis of a traditional single-level differential structure, a differential excitation unit consists of an alternating square wave voltage source and 4 differential switches, the alternating square wave voltage source is usually an alternating voltage source, so that a differential magnetic ring unit is in a saturated state, and the 4 differential switches are used for controlling and switching a positive excitation working state and a negative excitation working state to form a first-level differential; excitation windings of the two annular magnetic cores are connected in series in an opposite direction to form a second-stage differential; the differential detection unit consists of a current measuring device and 4 differential switches, the current measuring device consists of an AD chip and a microprocessor thereof, the output voltage of the differential magnetization unit is subjected to analog-to-digital conversion and data demodulation, and the 4 differential switches are used for controlling and switching the working states of positive detection and negative detection to form third-stage differential; the influence of the micro asymmetry of the excitation power supply and the detection loop on the sensor is greatly weakened, the resolution and the accuracy of weak current detection are further improved, a foundation is laid for advanced application of a smart grid, and the safe and stable operation of the system is guaranteed; the current measuring device is formed by the AD chip and the microprocessor thereof, the sampling precision is high, the extra error introduced by a detection loop is less, the working stability is good, and the foundation is laid for high-accuracy demodulation.
It should be noted that, in the foregoing embodiments, the description of each embodiment has an emphasis, and reference may be made to the related description of other embodiments for a part that is not described in detail in a certain embodiment.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While the preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (6)
1. An excitation-magnetization-detection three-stage differential weak current measuring device, comprising: a differential magnetization unit, a differential excitation unit and a differential detection unit;
the differential magnetization unit comprises an annular magnetic core C 1 And a toroidal core C 2 Said toroidal core C 1 Is provided with an excitation winding W e1 And a detection winding W D1 Said toroidal core C 2 Is provided with an excitation winding W e2 And a detection winding W D2 Said excitation winding W e1 And an excitation winding W e2 Reverse series connection, the detection winding W D1 And a detection winding W D2 Are connected in series;
the differential excitation unit comprises an alternating square wave voltage source, and two ends of the alternating square wave voltage source are respectively connected with the excitation winding W e1 And an excitation winding W e2 Is connected with one end of the connecting rod;
the differential detection unit comprises current measuring devices respectively connected with the detection winding W D1 And a detection winding W D2 Is connected with one end of the connecting rod;
setting the positive pole of the alternating square wave voltage source and the excitation winding W e1 Connecting the negative pole with the excitation winding W e2 When the differential magnetization unit is connected, the differential magnetization unit is in a positive working state; the positive electrode of the current measuring device and the detection winding W D1 Connecting the negative pole with the detection winding W D2 When the differential detection unit is connected, the differential detection unit is in a positive working state;
enabling the alternating square wave voltage source and the current measuring device to be respectively in four working states of positive and positive, positive and negative, negative and positive and negative, and calculating to obtain an output current value of the weak current measuring device according to four current measuring values of the current measuring device in the four working states;
the current measuring device comprises an AD chip and a microprocessor thereof; the AD chip and the microprocessor thereof collect n second output voltage signals OUT of the differential magnetization unit 1 For the output voltage signal OUT 1 Carrying out analog-to-digital conversion and data demodulation to obtain current measurement values in each working state; n is set sampling time;
using Fourier analysis algorithm to output voltage signal OUT 1 Carrying OUT data demodulation to obtain an output voltage signal OUT in the ith working state i After the second harmonic component, dividing the second harmonic component by a proportionality coefficient K to obtain the current measured value I under the ith working state mi ；
The output current value
The calculation formula of (c) is:
wherein the content of the first and second substances,
、
、
and
and the current measuring values respectively represent the current measuring values containing phase information when the alternating square wave voltage source and the current measuring device are respectively in four working states of positive, negative, positive and negative.
2. According toThe weak current measuring device of claim 1, further comprising a differential control module; the differential excitation units also respectively comprise differential switches S 11 、S 21 、S 12 And S 22 (ii) a The differential detection unit further comprises a differential switch S 33 、S 34 、S 43 And S 44 ；
The differential switch S 11 、S 21 、S 12 And S 22 The positive electrode and the negative electrode of the alternating square wave voltage source are respectively arranged on the excitation winding W e1 And the excitation winding W e2 The connecting branch of (2);
the differential switch S 33 、S 34 、S 43 And S 44 A positive electrode and a negative electrode respectively arranged on the current measuring device and the detection winding W D1 And the detection winding W D2 The connecting branch of (2);
the differential control module controls each differential switch S 11 、S 21 、S 12 、S 22 、S 33 、S 34 、S 43 And S 44 The alternating square wave voltage source and the current measuring device are in a positive working state or a negative working state.
3. The weak current measuring device according to claim 2, wherein the differential detection unit sends a switching signal to the differential control module after completing the current measurement in the positive working state, and the differential control module modifies the working states of the alternating square wave voltage source and the current measuring device into the positive working state and the negative working state after receiving the switching signal;
after finishing the current measurement of the positive and negative working states, the differential detection unit sends a switching signal to the differential control module, and the differential control module modifies the working states of the alternating square wave voltage source and the current measurement device into a negative and positive working state after receiving the switching signal;
after finishing the current measurement in the negative and positive working states, the differential detection unit sends a switching signal to the differential control module, and the differential control module modifies the working states of the alternating square wave voltage source and the current measurement device into the negative and negative working states after receiving the switching signal;
and the differential detection unit sends a switching signal to the differential control module after finishing the current measurement in a negative working state, and the differential control module modifies the working states of the alternating square wave voltage source and the current measurement device into a positive working state after receiving the switching signal.
4. The weak current measuring device according to claim 1, further comprising an output module;
the current measuring device outputs the measured current values under various working states to the output module, and the output module outputs the calculated output current values.
5. The weak current measuring device according to claim 1, wherein the current measuring device periodically and cyclically acquires current values in four operating states; the period is 4n seconds;
and calculating each period to obtain the output current value and then outputting the output current value.
6. Weak current measuring device according to claim 1, characterized in that said toroidal core C 1 And a toroidal core C 2 The dimension materials are the same;
the excitation winding W e1 And an excitation winding W e2 Are consistent.
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