CN112394219A - Current measuring device - Google Patents
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Abstract
The application relates to a current measuring device, which comprises a sensing circuit, an adding circuit and a processing unit, wherein the sensing circuit comprises a plurality of magnetic field measuring chips which are arranged at intervals and enclose a closed graph, each magnetic field measuring chip is respectively connected with the input end of the adding circuit, the output end of the adding circuit is connected with the processing unit, and a measured lead passes through the plane where the closed graph enclosed by the plurality of magnetic field measuring chips is located; the magnetic field measurement chips induce the current passing through the measured lead and output induced voltage to the addition circuit, the addition circuit adds the induced voltage output by each magnetic field measurement chip and outputs total voltage to the processing unit, and the processing unit obtains the current value of the measured lead according to the total voltage. By adopting the method, the defect that the measured lead needs to be positioned at the central position can be effectively overcome, the applicability is high, the iron loss caused by the iron core can be avoided, and the power consumption is reduced.
Description
Technical Field
The application relates to the technical field of electric power instrument testing, in particular to a current measuring device.
Background
With the increase of the transmission capacity and the improvement of the voltage grade of the power system and the proposal and the continuous maturity of the smart grid concept in recent years, higher requirements are put forward on the equipment for acquiring and detecting the grid signals, and especially, the equipment has updated promises on the aspects of accuracy, stability, rapidity and the like of acquiring the grid signals. Therefore, the device for measuring the current is more important as a power grid signal and an intermediate link of a computer system, for example, the accuracy and the real-time performance of the signal acquired by the current transformer influence the accurate analysis of the computer system on the fault.
Traditionally, current measurement is generally performed by using a measurement method of an electromagnetic current transformer or a rogowski coil. The measurement accuracy of the electromagnetic current transformer can reach a few thousandths, but the electromagnetic current transformer is influenced by an iron core, so that the iron loss and the power consumption are high. The Rogowski coil measurement method requires that a measured lead is positioned in the center of the coil to ensure that magnetic fields at all positions of the ring are equal, has certain requirements on the shape of the measured lead, and is low in applicability.
Disclosure of Invention
In view of the above, it is necessary to provide a current measuring device with low power consumption and high applicability.
A current measurement device comprising: the sensor circuit comprises a plurality of magnetic field measuring chips which are arranged at intervals and enclose a closed graph, each magnetic field measuring chip is connected with the input end of the adder circuit, the output end of the adder circuit is connected with the processing unit, and a measured wire penetrates through a plane where the closed graph enclosed by the plurality of magnetic field measuring chips is located;
the magnetic field measurement chips induce the current passing through the measured lead and output induced voltage to the addition circuit, the addition circuit adds the induced voltage output by each magnetic field measurement chip and outputs total voltage to the processing unit, and the processing unit obtains the current value of the measured lead according to the total voltage.
According to the current measuring device, the magnetic field measuring chip in the sensing circuit senses the current passing through the measured wire and outputs the sensing voltage to the adding circuit, the adding circuit adds the sensing voltages and outputs the total voltage to the processing unit, and the processing unit can obtain the current value of the measured wire according to the total voltage to realize the current measurement of the measured wire. The magnetic field measurement chips which are arranged at intervals to form a closed pattern are adopted for induction, the formed closed pattern can be designed at will according to needs, the placing position of the measured wire in the closed pattern can be random, the limitation to the middle of the closed pattern is not needed, the defect that the measured wire needs to be in the central position in the measurement method can be effectively avoided, and the applicability is high; and the use of the iron core is cancelled, so that the iron loss caused by the iron core is avoided, and the power consumption is reduced.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a block diagram of a current measuring device according to an embodiment;
FIG. 2 is a schematic diagram of a sensing circuit in one embodiment;
FIG. 3 is a schematic diagram of a sensing circuit in one embodiment;
FIG. 4 is a schematic diagram of a sensing circuit in yet another embodiment;
FIG. 5a is a graph showing the output of a TMR2503 chip as a function of the intensity of an applied magnetic field;
FIG. 5b is another graph of TMR2503 chip output as a function of applied magnetic field strength;
FIG. 6 is a circuit schematic of an adder circuit in one embodiment;
FIG. 7 is a block diagram showing the structure of a current measuring apparatus according to another embodiment;
FIG. 8 is a circuit schematic of a conditioning circuit in one embodiment;
FIG. 9 is a flow diagram illustrating the process of chip scale selection and current valid reading for the ADE7753 chip in one embodiment;
FIG. 10 is a schematic flow chart of the ratio and angle difference compensation in one embodiment;
FIG. 11 is a circuit schematic of a power management module in one embodiment.
Detailed Description
To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, a first resistance may be referred to as a second resistance, and similarly, a second resistance may be referred to as a first resistance, without departing from the scope of the present application. The first resistance and the second resistance are both resistances, but they are not the same resistance.
It is to be understood that "connection" in the following embodiments is to be understood as "electrical connection", "communication connection", and the like if the connected circuits, modules, units, and the like have communication of electrical signals or data with each other.
As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.
As shown in fig. 1 and 2, in one embodiment, there is provided a current measuring apparatus including: a sensing circuit 110, an adding circuit 130, and a processing unit 150; the sensing circuit 110 includes a plurality of magnetic field measurement chips 111 (refer to fig. 2) arranged at intervals to form a closed pattern, each magnetic field measurement chip 111 is connected to an input terminal of the adding circuit 130, an output terminal of the adding circuit 130 is connected to the processing unit 150, and a measured conductive wire passes through a plane where the closed pattern formed by the plurality of magnetic field measurement chips 111 is located. Specifically, the measured wire is placed within the range surrounded by the closed loop of the closed pattern at an angle to the plane of the closed pattern, that is, each magnetic field measurement chip 111 surrounds the measured wire, and more specifically, the measured wire may vertically pass through the plane of the closed pattern. Specifically, the surfaces of the magnetic field measurement chips 111 are in the same plane, which is the plane of the closed figure.
The magnetic field measurement chips 111 are arranged at intervals to form a closed pattern, which means that the arrangement path of the magnetic field measurement chips 111 is a closed pattern, and the magnetic field measurement chips 111 are not connected with each other. The shape of the closed figure can be designed arbitrarily according to requirements, such as a circle, a curved ring, a square and the like. Specifically, each magnetic field measurement chip 111 may be soldered on a hollow circuit board with a closed outline, and the shape of the circuit board may be designed according to different requirements.
The magnetic field measurement chip 111 generates an induced voltage by electromagnetic induction; specifically, the magnetic field measurement chip 111 senses the current passing through the wire to be measured, and outputs the sensed voltage to the adder circuit 130. As shown in FIG. 2, B1、B2、……、BnThe magnetic induction of the first magnetic field measurement chip, the magnetic induction of the second magnetic field measurement chip, … … and the magnetic induction of the nth magnetic field measurement chip, L1、L2、……、LnThe distance between the first magnetic field measurement chip and the second magnetic field measurement chip, the distance between the second magnetic field measurement chip and the third magnetic field measurement chip, … …, and the distance between the nth magnetic field measurement chip and the first magnetic field measurement chip are respectively. The addition circuit 130 is a circuit that can add and output an input voltage; specifically, the adder circuit 130 adds the induced voltages output from the magnetic field measurement chips 111 and outputs the total voltage to the processing unit 150. The processing unit 150 obtains the current value of the tested wire according to the total voltage. In particular, the amount of the solvent to be used,the processing unit 150 may include a device for converting the voltage value into a current value according to a preset corresponding relationship, and the processing unit 150 may process the voltage signal of the total voltage to obtain a corresponding current value.
In the current measuring device, the magnetic field measuring chip 111 in the sensing circuit 110 senses the current passing through the measured conductor and outputs the sensing voltage to the adding circuit 130, the adding circuit 130 adds the sensing voltages and outputs the total voltage to the processing unit 150, and the processing unit 150 can obtain the current value of the measured conductor according to the total voltage to realize the current measurement of the measured conductor. The magnetic field measurement chips 111 which are arranged at intervals to form a closed pattern are used for induction, the formed closed pattern can be designed at will according to needs, the placing position of the measured wire in the closed pattern can be random, the wire is not limited in the middle of the closed pattern, the defect that the measured wire needs to be in the central position in the measurement method can be effectively avoided, and the applicability is high; and the use of the iron core is cancelled, so that the iron loss caused by the iron core is avoided, and the power consumption is reduced.
In one embodiment, the magnetic field measurement chips 111 are single-axis magnetic field measurement chips, and the magnetic field sensitivity direction of each single-axis magnetic field measurement chip is directed to the middle position of the next adjacent single-axis magnetic field measurement chip.
For a single-axis magnetic field measurement chip, the magnetic field sensitivity direction is determined; adopt unipolar magnetic field to measure the chip, the sensitive direction of magnetic field of preceding unipolar magnetic field measurement chip points to the intermediate position of next unipolar magnetic field measurement chip to holistic sensitive direction of magnetic field is the same with the range trend of unipolar magnetic field measurement chip, winds the round and forms closed figure, can carry out electromagnetic induction to the wire of being surveyed of placing in closed figure.
For example, as shown in fig. 2, the magnetic field sensitivity direction of the first uniaxial magnetic field measurement chip is directed to the surface center point of the second uniaxial magnetic field measurement chip; according to the ampere-loop theorem, the magnetic induction is integrated along the line of any closed loop L, equal to μ, which is the algebraic sum of all currents through this loop0Multiple, as in equation (1) below.
The current direction complies with the right-hand rule, as shown in fig. 2, the current direction of the tested wire is vertical to the paper surface, and from outside to inside, complies with the right-hand rule.
In one embodiment, the plurality of magnetic field measurement chips 111 are arranged at equal intervals by a predetermined distance. That is, the magnetic field measurement chips 111 are equally spaced apart. Specifically, the preset distance may be set according to actual requirements.
If the magnetic field measurement chips 111 are arranged at unequal intervals, a large number of processing units 150 equal to the number of the magnetic field measurement chips 111 need to be designed, so that the circuit design of the whole current measurement device is very complicated, the size is increased, and the requirement of micro intelligence is not met. By arranging the magnetic field measurement chips 111 at equal intervals, simplification of a circuit structure can be avoided, and the size can be reduced.
Specifically, the preset distance may be 5mm (millimeter), that is, the distance between adjacent magnetic field measurement chips 111 is 5mm, the distance is moderate, and the effect is optimal.
The pattern enclosed by the magnetic field measurement chip 111 can be designed arbitrarily according to requirements, and is a closed loop. Aiming at application scenes such as an overhead conductor, a power distribution cabinet and the like of a power system, two circular sensing circuits and a bus bar type sensing circuit corresponding to the application scenes are designed, as shown in figures 3 and 4, it can be seen from the figures that the shapes of the overhead conductor or the bus bar type sensing circuit of the power distribution cabinet are arbitrary, and the arrangement position is not required to be the center.
In one embodiment, the magnetic field measurement chip 111 is a TMR2503 chip, i.e. the model of the chip is TMR 2503. The TMR2503 chip has a unique push-pull Wheatstone full-bridge structure design and comprises four non-shielding high-sensitivity TMR sensor elements which can sense a magnetic field vertical to the surface of the chip; when the external magnetic field changes along the direction vertical to the surface of the chip, the Wheatstone full bridge provides differential voltage output; the sensitivity and offset voltage of TMR2503 can be kept at a stable level in the range of-55 deg.C to +150 deg.C. Typical curves of TMR2503 chip output as a function of applied magnetic field strength (applied magnetic field strength. + -. 2000Oe and. + -. 200Oe, excitation power supply 1V) are shown in FIGS. 5a and 5 b. To ensure sensitivity, the TMR2503 chip generally works in its linear region (-200 GS), and it can be known from fig. 5b that the curve passes through the origin, and the relationship can be expressed by a unary linear equation as shown in the following equation (2):
U＝aB (2)
in the formula, a is a proportionality coefficient of a linear area of the chip; u is the differential voltage output by the Wheatstone full bridge of the chip; and B is the magnetic induction intensity measured by the chip.
Discretizing the formula (1) and combining the formula (2) to obtain the following formula (3):
in the formula, delta l is the arrangement and arrangement spacing of the magnetic field measurement chips,
are all constants, I is current.
In one embodiment, as shown in FIG. 6, the summing circuit 130 includes an operational amplifier U1AA first resistor R1A second resistor RfAnd a plurality of input resistances, the number of which is equal to the number of the magnetic field measurement chips 111. In FIG. 6, Ri1、Ri2、Ri3、……、RinRespectively a first input resistor, a second input resistor, a third input resistor, … …, an nth input resistor, U1、U2、U3、……、UnThe induced voltage output by the first magnetic field measurement chip, the induced voltage output by the second magnetic field measurement chip, the induced voltage output by the third magnetic field measurement chip, … … and the induced voltage output by the nth magnetic field measurement chip are respectively. Each magnetic field measurement chip 111 is connected with an operational amplifier U through a corresponding input resistor1AI.e. one magnetic field measuring chip 111 corresponds to one input resistor, the magnetic field measuring chip 111 is connected to one end of one input resistor, and the other end of the input resistor is connected toIs connected with an operational amplifier U1AThe same direction input end of the input terminal. Operational amplifier U1AThrough a first resistor R1Is grounded and passes through a second resistor RfConnecting operational amplifier U1AOf an operational amplifier U1AIs connected to the processing unit 150.
From equation (3), to obtain the current, it is necessary to calculate the sum of all the output voltages of the magnetic field measurement chip 111, and for this purpose, a non-inverting adder circuit is designed, which can calculate according to the "virtual break", "virtual short" and thevenin theorem:
as can be seen from FIG. 6, R is taken for designi1＝Ri2＝…＝RinThe expression may become:
if R is takenf＝(n-1)R1The expression can be changed to a perfect addition circuit, as shown in formula (6):
therefore, by designing the adder circuit 130, the induced voltages output from the magnetic field measurement chips can be added to output the total voltage VsumTo the processing unit 150.
Specifically, the addition circuit 130 may further include a resistor RpResistance RpOne end is connected with an operational amplifier U1AThe other end of the same-direction input end is grounded. In particular, an operational amplifier U1ALTC2051 may be employed; each input resistance and resistance RpMay be 10K ohms.
In one embodiment, referring to fig. 7, the processing unit 150 includes a conditioning circuit 151, a sampling circuit 152, and a processor 153, the conditioning circuit 151 is connected to the output of the adding circuit 130 and the sampling circuit 152, and the sampling circuit 152 is connected to the processor 153. The adding circuit 130 outputs the total voltage to the conditioning circuit 151, the conditioning circuit 151 conditions the total voltage, the sampling circuit 152 samples the conditioned voltage and outputs a digital signal to the processor 153, and the processor 153 obtains the current value of the tested wire according to the digital signal. By adopting the conditioning circuit 151, the sampling circuit 152 and the processor 153, the total voltage output by the adding circuit 130 is conditioned, sampled and a current value is obtained in sequence, and the obtained current value has high accuracy.
In one embodiment, referring to fig. 8, conditioning circuit 151 includes a first voltage divider resistor R20A second voltage dividing resistor R21A third voltage dividing resistor R22Capacitor C20A differential following operational amplifier circuit 1512 and a filter circuit 1513. First voltage dividing resistor R20One end of the voltage divider is connected to the output end of the adder 130, and the other end is connected to the second divider resistor R21Grounded, third voltage dividing resistor R22One terminal of (1), a capacitor C20One end of the differential follower operational amplifier 1512 and the first input end of the differential follower operational amplifier are connected to a first voltage dividing resistor R20And a second voltage dividing resistor R21A third divider resistor R22Another terminal of (1), a capacitor C20The other end of the differential follower operational amplifier 1512 and the second input end of the differential follower operational amplifier 1512 are grounded, and the output end of the differential follower operational amplifier 1512 is connected to the sampling circuit 152 through the filter circuit 1513.
The total voltage output from the adding circuit 130 passes through the first voltage dividing resistor R20A second voltage dividing resistor R21And a third voltage dividing resistor R22After the voltage division, the voltage is outputted to the filter circuit 1513 via the differential follower operational amplifier circuit 1512 for filtering, so as to obtain a conditioned voltage, and the conditioned voltage is outputted to the sampling circuit 152. By conditioning filtering, the accuracy of the signal can be improved.
In one embodiment, referring to FIG. 8, the differential follower op-amp circuit 1512 includes a voltage follower U1BResistance R23Resistance R24Resistance R25And a resistance R26. Resistance R23As a differenceThe first input end of the following operational amplifier 1512 is connected to the first voltage dividing resistor R20And a second voltage dividing resistor R21Common terminal of (3), resistor R23The other end of the voltage follower U is connected with a voltage follower U1BAnd through a resistor R24Grounding; resistance R25One end of the differential follower operational amplifier 1512 is used as a second input end, ground, and resistor R25The other end of the voltage follower U is connected with a voltage follower U1BAnd a voltage follower U1BIs passed through a resistor R26Connecting voltage follower U1BAn output terminal of (a); voltage follower U1BIs connected to the filter circuit 1513. By adopting the differential following operational amplifier 1512 of this structure, the voltage follower U1BThe high-frequency-conversion-ratio frequency divider is used as a buffer stage or an isolation stage, can improve input impedance and reduce output impedance, and has a good signal conditioning effect.
In one embodiment, the filter circuit 1513 includes a resistor R27And a capacitor C21Resistance R27One end is connected with a voltage follower U1BThe other end of the output terminal is connected to the sampling circuit 152 and passes through the capacitor C21And (4) grounding. By using a resistor R27And a capacitor C21And the filtering is carried out, and the structure is simple.
In one embodiment, the sampling circuit 152 includes a power metering chip, which is connected to the conditioning circuit 151 and the processor 153. The signals processed by the conditioning circuit 151 must be a/D (analog/digital) converted before being sent to the processor 153. The electric energy metering chip can perform A/D conversion on the sampled voltage signal, and calculate to obtain a current effective value, so that the processor 153 can read and use the current effective value conveniently.
The a/D conversion must take into account the matching of resolution and analog input voltage range. In order to make the transmitted data more accurate, it is often desirable that the amplitude of the received signal be very close to the upper limit of the range of the a/D input voltage. In most previous researches, the point is usually ignored, so that contradiction occurs between measuring range and measuring precision, and the application researches a wide-range current measuring device, namely, signals with different amplitudes are amplified by adopting a method of changing the gain of an amplifier; in order to meet the current signals in different measurement ranges and improve the resolution of A/D conversion, the precision of a processing system is improved, the programmable gain amplifier can be used with the A/D to adjust the gain of an input signal, the dynamic change of an input analog signal is allowed in a larger range, and the purpose of expanding the A/D input voltage range is achieved.
In light of the above need for a programmable gain amplifier, in one embodiment, the power metering chip employs an ADE7753 chip. The ADE7753 chip internally contains a programmable gain amplifier register, the gain of which can be selected from 1, 2, 4, 8 and 16, and the output signal can be accurately restored. The maximum differential input voltage at the V1P/V1N end of the ADE7753 chip is +/-0.5V, the gain of the programmable gain amplifier can be selected to be 1, 2, 4, 8 and 16, and the maximum input range of the A/D can be set to be 0.5V, 0.25V, 0.125V, 0.0625V, 0.0313V, 0.0156V and 0.00781V respectively by setting 3 bits and 4 bits in a register of the programmable gain amplifier, namely, the adaptive adjustment of the channel input voltage range is realized by adjusting ADC reference. Specifically, as shown in fig. 9, after the ADE7753 chip is initialized and a signal is collected into the ADE7753 chip, a gain is selected, which is designed by a programmable gain amplifier register, because the signal received for the first time is unknown, in order to avoid the influence on the ADE7753 chip caused by the signal exceeding the range set by the programmable gain amplifier register, the gain is set to 1 when sampling is performed for the first time, and the maximum input range of the ADC is set to 0.5V, so that the influence on the ADE7753 chip caused by the external signal being too large and exceeding the range is avoided. After the first amplification, the signals are converted into digital signals through the ADC, then the current effective value is calculated, and the magnitude of the electromotive force signals collected by the channel for the first time is reversely deduced according to the current effective value calculated for the first time and the effective value calculation formula. Based on the size, the corresponding input range is selected, which is the selection of the input range (also called gear selection). According to the selection, the programmable gain amplifier register is reinitialized, proper gain and ADC maximum range are selected for the input signal, then effective value calculation is carried out, and the result is output and displayed.
The offset correction is to complete the adjustment of the offset of the channel by writing the offset correction register of the a/D chip. The register can correct the offset of +/-20 mV to +/-50 mV, and the adjustment of the offset can be set by the gain.
Specifically, a standard current signal can be output by the standard signal generating means, and the optimum matching coefficient m can be easily found by the least square method by sampling the obtained voltage sum, and the formula (3) and the formula (6), and the square sum of the error between these found data and the actual data is minimized. The calculation formulas of the ratio difference and the angle difference are as follows:
wherein i1And i2One of which is the current of the standard current signal and the other of which is the current of the signal under test. As shown in fig. 10, the discrete waveform of the original signal is restored to a corresponding analog signal by a spline interpolation method, then the analog signal is sampled at the same time point according to the sampling point of the measured signal, the current value and the current difference value at the same time point are successively calculated to obtain the magnitude of the ratio difference and the angular difference, and then the measured signal is multiplied by the ratio difference value and subtracted by the angular difference value, so that the compensation of the ratio difference and the angular difference can be realized.
The ADE7753 chip omits a plurality of external analog circuits, reduces external interference, and for the specific error and angular error of the current measuring device, the ADE7753 chip also specially contains a compensation register of the angular error and the specific error, and a circuit for calculating the effective value of the current, so that the effective value of the current can be directly obtained through the register, the calculation of a program in the processor 153 is not needed, and the processing speed of the processor 153 is improved.
In one embodiment, the processor 153 is implemented as a nRF52840 chip, which is a bluetooth low energy system on chip. The nRF52840 chip adopts a 64MHz and 32-bit processor, has sufficient general processing capacity, floating point operation and DSP performance, has a built-in PA (power amplifier), has transmitting power up to +8dBm, is built in a 1MB Flash and a 256kB RAM, fully supports Bluetooth 5, 802.15.4 (including Thread), ANT and private 2.4GHz wireless technologies, is provided with a full-speed USB 2.0 controller and a series of peripheral devices, comprises a four-channel SPI interface, and meets the requirements of reading, correcting and gain amplification adjustment of sampling value data of A/D conversion.
In one embodiment, with continued reference to fig. 7, the current measuring apparatus further includes a communication module 180 connected to the processing unit 150, the communication module 180 is configured to be communicatively connected to an external device, and the processing unit 150 transmits the current value of the measured wire to the external device through the communication module 180. The current value is sent to the external equipment through the communication module 180, so that the communication between the current measuring device and the external equipment can be realized, the intelligent and digital development of the power system is realized, and the external equipment can be an upper computer, control equipment, equipment comprising a measurement protection system and the like. Specifically, the communication module 180 is a bluetooth communication module. The bluetooth communication module may be an ANT technology using nRF52840 chip to implement bluetooth communication.
In one embodiment, with continued reference to fig. 7, the current measuring apparatus further includes a power management module 170, wherein the power management module 170 is connected to the power supply device, and is connected to the sensing circuit 110, the adding circuit 130 and the processing unit 150. The power supply device is a device for outputting voltage to supply power, and may be a battery, for example. The power management module 170 supplies the voltage output from the power supply device to the sensing circuit 110, the adding circuit 130, and the processing unit 150, thereby supplying power to the sensing circuit 110, the adding circuit 130, and the processing unit 150.
In one embodiment, referring to fig. 11, the power management module 170 includes a current sensing power-taking device (not shown), a voltage doubling rectifying circuit 172, a comparator 173, an analog switch 174, and a voltage regulator 175, wherein the tested wire passes through the current sensing power-taking device, the voltage doubling rectifying circuit 172 is connected to the current sensing power-taking device, the comparator 173, and the analog switch 174, the analog switch 174 is further connected to the power supply device, the comparator 173, and the voltage regulator 174 is connected to the sensing circuit 110, the adding circuit 130, and the processing unit 150.
The current sensing energy-taking device is used for sensing the current of the tested wire and outputting the voltage to the voltage-multiplying rectifying circuit 172. The voltage doubler rectifier circuit 172 outputs the voltage doubler to the comparator 173. The comparator 173 controls the analog switch 174 to select the voltage of the power supply device or the voltage output from the voltage doubling rectifying circuit 172 according to the comparison result between the voltage doubled and the preset voltage threshold, and outputs the voltage to the voltage stabilizer 175, and the voltage stabilizer 175 stabilizes the input voltage and outputs the stabilized voltage, thereby supplying power to the sensing circuit 110, the adding circuit 130, and the processing unit 150. The current sensing energy obtaining device is used for obtaining energy of the tested lead as one power supply mode, the external power supply equipment is used as the other power supply mode, one of the two power supply modes is selected through the analog switch 174 according to the comparison result of the comparator 173, the self-power supply and the external power supply can be switched, and the power supply is convenient.
The current induction energy-taking device has an electromagnetic induction function, is provided with a hollow ring structure, and a measured lead penetrates through the hollow ring structure, so that the current induction energy-taking device induces the current of the measured lead to obtain a generated voltage. Specifically, the current induction energy-taking device may be a Current Transformer (CT) obtained by winding about 2000 turns using permalloy having a high magnetic permeability in a weak magnetic field as a magnetic core.
The voltage doubler rectifier circuit 172 is a circuit that can double the input voltage and output the voltage. In one embodiment, referring to fig. 11, the voltage-doubling rectifying circuit includes a capacitor C10, a capacitor C11, a diode D10 and a diode D11, one end of the capacitor C10 is connected to the current sensing energy-extracting device, and the other end is connected to the cathode of the diode D10 and the anode of the diode D11; the anode of the diode D10 is connected to the current sensing and energy extracting device and to ground, the cathode of the diode D11 is connected to the comparator 173 and the analog switch 174, one end of the capacitor C11 is connected to the comparator 173 and the analog switch 174, and the other end is connected to ground. The voltage doubling rectifying circuit 172 utilizes the storage effect of the capacitor on the charge to make the output voltage be twice of the input voltage, which is the voltage doubling rectifying scheme. Specifically, the diode D10 and the diode D11 adopt IN4148WS, and the capacitor C10 and the capacitor C11 adopt a capacitance of 680 uF. The initial starting current is designed to be 2A, and the output voltage is 3V after voltage doubling rectification and the final voltage stabilizer 175.
In one embodiment, referring to fig. 11, the comparator 173 includes a comparison chip, a resistor R10, a resistor R11, and a resistor R12, wherein the resistor R10, the resistor R11, and the resistor R12 are sequentially connected in series, and the other end of the resistor R10 is connected to the voltage-doubling rectifying circuit 172, and the other end of the resistor R12 is grounded; the common end of the resistor R10 and the resistor R11 is connected with the low-voltage input port Lth of the comparison chip, and the common end of the resistor R11 and the resistor R12 is connected with the high-voltage input port Hth of the comparison chip; the output of the comparison chip is connected to the analog switch 174 for providing an enable signal to the analog switch 174 to control the selection of the analog switch 174. Specifically, a voltage threshold may be designed by using the comparison chip MIC833 with a reference potential, and the high voltage threshold is:
VHth＝Vref×[(R10+R11+R12)/R12] (14)
low voltage threshold VLthComprises the following steps:
VLth＝Vref×[(R10+R11+R12)/(R11+R12)] (15)
in particular, V can be designedHthAnd VLth3.56V and 2.49V, respectively, i.e. the preset voltage threshold comprises 3.56V and 2.49V.
Specifically, the analog switch 174 may be an analog switch of the TPS2105 series, and the voltage regulator 175 may be a voltage regulator chip of the AMS1117 series. The comparison chip MIC833 is used for comparing the voltage after voltage doubling with a preset voltage threshold value to judge an enable signal generated so as to control the analog switch 174 to select whether the battery supply or the CT energy taking supply is performed, and then the voltage stabilizing chip AMS1117 is used for stabilizing the output voltage at 3V to supply power to the sensing circuit 110, the adding circuit 130, the conditioning circuit 151, the sampling circuit 152, the processor 153 and the communication module 180. For example, the comparison chip MIC833 may provide an enable signal to the analog switch 174 when the voltage after voltage doubling is greater than 3.56V, and the analog switch 174 selects to switch in the voltage output by the voltage doubling rectifying circuit 172, and if no enable signal is present, the analog switch 174 selects to switch in the voltage output by the battery. Therefore, the current induction energy taking device can be preferentially selected when the voltage output by the current induction energy taking device meets the requirement, the use of a battery is reduced, and the battery is more environment-friendly.
The conventionally used electromagnetic current transformer including an iron core has further problems including: when measuring high voltage level, generally adopt the oil-immersed insulation, when the overvoltage overcurrent trouble appears, it is very easy to happen the fire disaster or explosion situation, have flammable and explosive problem; moreover, because the electromagnetic mutual inductor is designed according to an electromechanical relay, the higher the voltage grade of the equipment is, the larger the corresponding volume is, and the problem of large volume exists; the output interfaces are incompatible, and the output current signals can be transmitted to an upper computer after being properly processed under the general condition, however, the electromagnetic current transformer cannot be connected with control equipment due to the fact that no corresponding interface exists on the secondary side, and therefore the electromagnetic current transformer cannot adapt to the development of intellectualization and digitization of a power system at the present stage. The current measuring device provided by the application is based on loop multi-magnetic field measurement combination, oil immersion type insulation is not used, the problem of flammability and explosion is avoided, an iron core is not arranged in an insulation framework, iron loss is avoided, power consumption is low, insulation performance is good, the size is small, the weight is light, the measurement frequency band is wide, magnetic saturation is avoided, linearity is good, environmental friendliness is high, manufacturing cost is low, a secondary side can be opened, the measured current value can be directly provided for a measurement protection system and can be directly connected with secondary equipment for system integration, secondary equipment is simplified, the current power system large-power-generating capacity and high-voltage-level requirements are met, the defects that measured wires need to be located in the center of a coil and can be guaranteed to be equal in magnetic fields at all annular positions by means of measurement methods such as Rogowski coils and certain requirements are met on the shapes of the measured wires are overcome, and the applicability.
In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A current measuring device, comprising: the sensor circuit comprises a plurality of magnetic field measuring chips which are arranged at intervals and enclose a closed graph, each magnetic field measuring chip is connected with the input end of the adder circuit, the output end of the adder circuit is connected with the processing unit, and a measured wire penetrates through a plane where the closed graph enclosed by the plurality of magnetic field measuring chips is located;
the magnetic field measurement chips induce the current passing through the measured lead and output induced voltage to the addition circuit, the addition circuit adds the induced voltage output by each magnetic field measurement chip and outputs total voltage to the processing unit, and the processing unit obtains the current value of the measured lead according to the total voltage.
2. The current measuring device of claim 1, wherein the magnetic field measuring chips are uniaxial magnetic field measuring chips, and the magnetic field sensitivity direction of each uniaxial magnetic field measuring chip is directed to an intermediate position of a next adjacent uniaxial magnetic field measuring chip.
3. The current measuring device according to claim 1, wherein the plurality of magnetic field measuring chips are arranged at equal intervals at a predetermined distance.
4. The current measuring device of claim 1, wherein the summing circuit comprises an operational amplifier, a first resistor, a second resistor, and a plurality of input resistors equal in number to the number of magnetic field measuring chips;
each magnetic field measurement chip is connected with the equidirectional input end of the operational amplifier through a corresponding input resistor, the reverse input end of the operational amplifier is grounded through the first resistor and is connected with the output end of the operational amplifier through the second resistor, and the output end of the operational amplifier is connected with the processing unit.
5. The current measuring device of claim 1, wherein the processing unit comprises a conditioning circuit, a sampling circuit, and a processor, the conditioning circuit coupled to the output of the summing circuit and the sampling circuit, the sampling circuit coupled to the processor.
6. The current measuring device of claim 5, wherein the conditioning circuit comprises a first voltage dividing resistor, a second voltage dividing resistor, a third voltage dividing resistor, a capacitor, a differential following operational amplifier circuit and a filter circuit;
one end of the first voltage-dividing resistor is connected with the output end of the addition circuit, the other end of the first voltage-dividing resistor is grounded through the second voltage-dividing resistor, one end of the third voltage-dividing resistor, one end of the capacitor and the first input end of the differential following operational amplifier circuit are all connected with the common end of the first voltage-dividing resistor and the common end of the second voltage-dividing resistor, the other end of the third voltage-dividing resistor, the other end of the capacitor and the second input end of the differential following operational amplifier circuit are grounded, and the output end of the differential following operational amplifier circuit is connected with the sampling circuit through the filter circuit.
7. The current measurement device of claim 5, wherein the sampling circuit comprises an electrical energy metering chip that connects the conditioning circuit and the processor.
8. The current measurement device of claim 1, further comprising a power management module coupled to a power supply and to the sensing circuit, the summing circuit, and the processing unit.
9. The current measuring device according to claim 8, wherein the power management module comprises a current sensing energy obtaining device, a voltage doubling rectifying circuit, a comparator, an analog switch and a voltage stabilizer, the tested wire passes through the current sensing energy obtaining device, the voltage doubling rectifying circuit is connected with the current sensing energy obtaining device, the comparator and the analog switch, the analog switch is further connected with the power supply device, the comparator and the voltage stabilizer, and the voltage stabilizer is connected with the sensing circuit, the adding circuit and the processing unit;
the current sensing energy-obtaining device is used for sensing the current of the tested wire and outputting voltage to the voltage-multiplying rectification circuit, the voltage-multiplying rectification circuit outputs the voltage after voltage multiplication to the comparator, the comparator controls the analog switch to select the voltage of the power supply providing equipment or the voltage output by the voltage-multiplying rectification circuit according to the comparison result of the voltage after voltage multiplication and a preset voltage threshold value and outputs the voltage to the voltage stabilizer, and the voltage stabilizer stabilizes the input voltage and outputs the stabilized voltage.
10. The current measuring device according to claim 1, further comprising a communication module connected to the processing unit, wherein the communication module is configured to be connected to an external device in a communication manner, and the processing unit transmits the current value of the measured wire to the external device through the communication module.
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| CN113391116A (en) * | 2021-03-17 | 2021-09-14 | 清华大学 | Sensor array for measuring bus current |
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Application publication date: 20210223 |