CN114019222A - Half-wave detection method and detection circuit for high-precision measurement of residual current - Google Patents
Half-wave detection method and detection circuit for high-precision measurement of residual current Download PDFInfo
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- 238000006243 chemical reaction Methods 0.000 claims description 38
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R19/145—Indicating the presence of current or voltage
- G01R19/15—Indicating the presence of current
Abstract
The invention relates to a half-wave detection method and a detection circuit for high-precision measurement of residual current, wherein the method comprises the following steps: sampling ADC values of a plurality of points at equal intervals in the positive half period of the alternating current signal through a residual current sampling circuit; calculating effective values of ADC values of a plurality of points of sampling through an effective value algorithm; calculating the current value of the residual current signal according to the mapping relation between the real residual current signal and the effective value; by applying the method, ADC values of a plurality of points are sampled at equal intervals in the positive half period of the alternating current signal through the residual current sampling circuit, then the effective value of the sampled ADC values of the plurality of points is calculated by utilizing an effective value algorithm, and finally the current value of the residual current signal is calculated according to the mapping relation between the real residual current signal and the effective value; the main work is completed by software calculation, the detection speed is high, the detection accuracy is high, and the development cost and time can be effectively saved.
Description
Technical Field
The invention relates to the technical field of monitoring of fire-fighting equipment, in particular to a half-wave detection method and a half-wave detection circuit for high-precision measurement of residual current.
Background
The residual current detection has extensive application in the aspect of fire-fighting equipment monitoring, and the residual current detection that can be accurate quick has huge meaning to consumer. The currently adopted residual current detection usually adopts a direct current offset detection means, and a method capable of rapidly and simply detecting an alternating current signal does not exist.
Disclosure of Invention
The present invention provides a half-wave detection method for high-precision measurement of residual current, and also provides a half-wave detection circuit for high-precision measurement of residual current, aiming at the above-mentioned defects in the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a half-wave detection method for high-precision measurement of residual current is constructed, and comprises the following steps:
the first step is as follows: sampling ADC values of a plurality of points at equal intervals in the positive half period of the alternating current signal through a residual current sampling circuit;
the second step is that: calculating effective values of ADC values of a plurality of points of sampling through an effective value algorithm;
the third step: and calculating the current value of the residual current signal according to the mapping relation between the real residual current signal and the effective value.
The invention relates to a half-wave detection method for measuring residual current with high precision, wherein a residual current sampling circuit adopted in the first step comprises the following steps: the first switch-in end and the second switch-in end are respectively and correspondingly connected with two output signal ends of the residual current transformer, the first conversion resistor is used for converting the switched-in current signal into a voltage signal, and the first amplifier is used for amplifying the converted voltage signal;
the sampling method in the first step is to connect the output end of the first amplifier to sample signals through the ADC analog sampling port of the singlechip.
The invention relates to a half-wave detection method for high-precision measurement of residual current, wherein a first access end and a second access end are respectively connected with two ends of a first conversion resistor, one end of the first conversion resistor is connected with a non-inverting input end of a first amplifier, and the other end of the first conversion resistor is grounded; the output end of the first amplifier is connected with a first resistor, and the inverting input end of the first amplifier is connected with a second resistor and a third resistor in parallel; the end of the third resistor, which is far away from the end connected with the first amplifier, is grounded, and the end of the second resistor, which is far away from the inverting input end of the first amplifier, is connected with the end of the first resistor, which is connected with the first amplifier; the negative power supply end of the first amplifier is grounded, and the negative power supply end of the first amplifier is connected with one end, far away from the first amplifier, of the first resistor through a first capacitor.
The invention relates to a half-wave detection method for high-precision measurement of residual current, wherein a first TVS (transient voltage suppressor) tube and a second capacitor are connected in parallel at a first access end; one end, far away from the first access end, of the first TVS tube is connected with the second access end; one end, far away from the first access end, of the second capacitor is connected with the second access end; and a fourth resistor is connected in series at one end of the first conversion resistor, which is far away from the first access end, and one end of the fourth resistor, which is far away from the first conversion resistor, is connected with the non-inverting input end of the first amplifier.
The invention relates to a half-wave detection method for high-precision measurement of residual current, wherein in the third step, the current value of a residual current signal is calculated according to the mapping relation between a real residual current signal and an effective value by using a formula:
Xrms＝IS/Nb*R5*(R2+R3)/R3/3.3*4096；
wherein Xrms is the effective value obtained in the second step; IS IS the current value of the residual current; nb is the amplification factor of the current transformer; r5 is the first conversion resistance value; r2 is a second resistance value; r3 is the third resistance value.
The invention relates to a half-wave detection method for high-precision measurement of residual current, wherein the method adopted in the first step is as follows:
equidistant sampling is carried out in a complete alternating current signal period to obtain a plurality of sampling data, signals in a positive half period are amplified through a residual current sampling circuit, signals in a negative half period are filtered, and ADC values of a plurality of points sampled at equal intervals in the positive half period of the alternating current signals are obtained.
The invention relates to a half-wave detection method for high-precision measurement of residual current, wherein in the second step, the effective values of ADC values of a plurality of points to be sampled are calculated by an effective value algorithm by adopting the following steps:
and (3) obtaining an effective value by a root mean square algorithm according to a plurality of point ADC values collected in the positive half period of the alternating current signal obtained in the first step, and then multiplying the effective value by the coefficient proportion of a hardware circuit to obtain an actual effective value.
A half-wave detection circuit for high-precision measurement of residual current comprises a third access end and a fourth access end which are respectively and correspondingly connected with two output signal ends of a residual current transformer, a second conversion resistor for converting an accessed current signal into a voltage signal, and a second amplifier for amplifying the converted voltage signal; the third access end and the fourth access end are respectively connected with two ends of the second conversion resistor, one end of the second conversion resistor is connected with the non-inverting input end of the second amplifier, and the other end of the second conversion resistor is grounded;
the output end of the second amplifier is connected with a fifth resistor, and the inverting input end of the second amplifier is connected with a sixth resistor and a seventh resistor in parallel; one end of the seventh resistor, which is far away from the end connected with the second amplifier, is grounded, and one end of the sixth resistor, which is far away from the inverting input end of the second amplifier, is connected with one end of the fifth resistor, which is connected with the second amplifier; the negative power supply end of the second amplifier is grounded, and the negative power supply end of the second amplifier is connected with one end, far away from the second amplifier, of the fifth resistor through a third capacitor.
According to the half-wave detection circuit for measuring the residual current with high precision, the third access end is connected with the second TVS tube and the fourth capacitor in parallel; one end, far away from the third access end, of the second TVS tube is connected with the fourth access end; one end, far away from the third access end, of the fourth capacitor is connected with the fourth access end; an eighth resistor is connected in series to one end, far away from the third access end, of the second conversion resistor, and one end, far away from the second conversion resistor, of the eighth resistor is connected with the non-inverting input end of the second amplifier.
The invention has the beneficial effects that: by the method, ADC values of a plurality of points are sampled at equal intervals in the positive half period of the alternating current signal through the residual current sampling circuit, effective values of the sampled ADC values of the plurality of points are calculated by using an effective value algorithm, and finally, the current value of the residual current signal is calculated according to the mapping relation between the real residual current signal and the effective values, without direct current offset.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the present invention will be further described with reference to the accompanying drawings and embodiments, wherein the drawings in the following description are only part of the embodiments of the present invention, and for those skilled in the art, other drawings can be obtained without inventive efforts according to the accompanying drawings:
FIG. 1 is a flow chart of a half-wave detection method for high-precision measurement of residual current according to a preferred embodiment of the present invention;
FIG. 2 is a circuit diagram of a residual current sampling method for half-wave detection of high precision measurement of residual current according to a preferred embodiment of the present invention;
FIG. 3 is a schematic diagram of the application of the residual current transformer of the three-phase power distribution system according to the half-wave detection method for measuring the residual current with high precision in the preferred embodiment of the invention;
FIG. 4 is a schematic diagram of the application of the residual current transformer of the single-phase distribution system according to the half-wave detection method for measuring the residual current with high precision in the preferred embodiment of the present invention;
FIG. 5 is a waveform diagram of the AINO end output of the half-wave detection method for measuring the residual current with high precision in accordance with the preferred embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without inventive step, are within the scope of the present invention.
The half-wave detection method for high-precision measurement of residual current according to the preferred embodiment of the present invention is shown in fig. 1, and also shown in fig. 2-5, and includes the following steps:
s01: sampling ADC values of a plurality of points at equal intervals in the positive half period of the alternating current signal through a residual current sampling circuit;
s02: calculating effective values of ADC values of a plurality of points of sampling through an effective value algorithm;
s03: and calculating the current value of the residual current signal according to the mapping relation between the real residual current signal and the effective value.
By applying the method, ADC values of a plurality of points are sampled at equal intervals in the positive half period of the alternating current signal through the residual current sampling circuit, then the effective value of the sampled ADC values of the plurality of points is calculated by utilizing an effective value algorithm, and finally the current value of the residual current signal is calculated according to the mapping relation between the real residual current signal and the effective value; the main work is completed by software calculation, the detection speed is high, the detection accuracy is high, and the development cost and time can be effectively saved.
It should be noted that, the application of the residual current transformer is shown in fig. 3, in a three-phase power distribution system, A, B, C, N four wires should simultaneously pass through the residual current transformer, and as shown in fig. 4, in a single-phase power distribution system, L, N two wires should simultaneously pass through the residual current transformer;
preferably, the residual current sampling circuit used in the first step includes: the first switch-in end and the second switch-in end are respectively and correspondingly connected with two output signal ends of the residual current transformer, the first conversion resistor is used for converting the switched-in current signal into a voltage signal, and the first amplifier is used for amplifying the converted voltage signal;
as shown in fig. 2, two output signals of the residual current transformer are respectively connected to two CT _ INPUT ends (a first connection end and a second connection end), the current is converted into a voltage signal through a first conversion resistor R5 and then amplified through a first amplifier U1, then the voltage signal is sampled through an ADC analog sampling port which is transmitted to the single chip microcomputer through AIN0, the current is connected to the INPUT end of an operational amplifier through the residual current transformer, the voltage at the central point is not lifted, the introduction of errors is reduced, the signal positive periodic signal is directly amplified and output, and an actual value is obtained through the operation of a CPU.
The first step of the sampling method is to connect the output end of the first amplifier to sample signals through the ADC analog sampling port of the singlechip.
Preferably, the first access terminal (upper CT _ INPUT port in fig. 2) and the second access terminal (lower CT _ INPUT port in fig. 2) are respectively connected to two ends of a first conversion resistor R5, one end of the first conversion resistor R5 is connected to the non-inverting INPUT terminal of the first amplifier U1, and the other end of the first conversion resistor R5 is grounded; the output end of the first amplifier U1 is connected with a first resistor R1, and the inverting input end of the first amplifier U1 is connected with a second resistor R2 and a third resistor R3 in parallel; the end of the third resistor R3, which is far away from the end connected with the first amplifier U1, is grounded, and the end of the second resistor R2, which is far away from the inverting input end of the first amplifier U1, is connected with the end of the first resistor R1 connected with the first amplifier U1; the negative power supply end of the first amplifier U1 is grounded, and the negative power supply end of the first amplifier U1 is connected with the end of the first resistor R1 away from the first amplifier U1 through a first capacitor C1. Preferably, the first connecting end is connected in parallel with a first TVS transistor TVS1 and a second capacitor C2; one end of the first TVS tube TVS1 far from the first incoming end is connected to the second incoming end; one end of the second capacitor C2 far away from the first access end is connected with the second access end; the end of the first switching resistor R5 away from the first access end is connected in series with a fourth resistor R4, and the end of the fourth resistor R4 away from the first switching resistor R5 is connected to the non-inverting input end of the first amplifier U1.
Preferably, in the third step, the current value of the residual current signal is calculated according to the mapping relationship between the real residual current signal and the effective value by using a formula:
Xrms＝IS/Nb*R5*(R2+R3)/R3/3.3*4096；
wherein Xrms is the effective value obtained in the second step; IS IS the current value of the residual current; nb is the amplification factor of the current transformer; r5 is the first conversion resistance value; r2 is a second resistance value; r3 is a third resistance value; through this kind of mode, just can be very convenient and fast and accurate detect the current value of residual current.
Preferably, the method adopted in the first step is as follows:
equidistant sampling is carried out in a complete alternating current signal period to obtain a plurality of sampling data, signals in a positive half period are amplified through a residual current sampling circuit, signals in a negative half period are filtered, and ADC values of a plurality of points sampled at equal intervals in the positive half period of the alternating current signals are obtained.
Preferably, the period of the alternating current signal is 20MS, 512 times of equal-interval sampling are carried out in 20MS to obtain 512 sampling data, only the signals of the positive half period are amplified through the residual current sampling circuit, the signals of the negative half period are filtered, therefore, the 512 points are sequenced, and 256 points in the positive sequence (large value) direction are used for carrying out the root mean square effective value algorithm;
preferably, in the second step, the effective value of the ADC values of the plurality of sampled points is calculated by an effective value algorithm by the following method:
obtaining an effective value by a root mean square algorithm for a plurality of point ADC values collected in the positive half period of the alternating current signal obtained in the first step, and then multiplying the effective value by the coefficient proportion of a hardware circuit to obtain an actual effective value;
the formula adopted for calculation is as follows:
preferably, the analog signal is accessed to an ADC interface of the processing unit during sampling to obtain 256 ADC values of points acquired in the positive half cycle of the ac signal, and an effective value is obtained by a root-mean-square algorithm and then multiplied by a coefficient ratio of a hardware circuit to obtain an actual effective value.
A half-wave detection circuit for high-precision measurement of residual current, see fig. 2, includes two third and fourth access terminals respectively connected to two output signal terminals of a residual current transformer, a second conversion resistor for converting an accessed current signal into a voltage signal, and a second amplifier for amplifying the converted voltage signal; the third access end and the fourth access end are respectively connected with two ends of a second conversion resistor, one end of the second conversion resistor is connected with the non-inverting input end of the second amplifier, and the other end of the second conversion resistor is grounded; the output end of the second amplifier is connected with a fifth resistor, and the inverting input end of the second amplifier is connected with a sixth resistor and a seventh resistor in parallel; one end of the seventh resistor, which deviates from the connection with the second amplifier, is grounded, and one end of the sixth resistor, which deviates from the inverting input end of the second amplifier, is connected with one end of the fifth resistor, which is connected with the second amplifier; the negative power supply end of the second amplifier is grounded, and the negative power supply end of the second amplifier is connected with one end, far away from the second amplifier, of the fifth resistor through the third capacitor. The third access end is connected with a second TVS tube and a fourth capacitor in parallel; one end, far away from the third access end, of the second TVS tube is connected with the fourth access end; one end of the fourth capacitor, which is far away from the third access end, is connected with the fourth access end; an eighth resistor is connected in series at one end of the second conversion resistor, which is far away from the third access end, and one end of the eighth resistor, which is far away from the second conversion resistor, is connected with the non-inverting input end of the second amplifier.
The circuit is the same as the circuit in the above, and the principle and the function are not repeated;
it will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (9)
1. A half-wave detection method for high-precision measurement of residual current is characterized by comprising the following steps:
the first step is as follows: sampling ADC values of a plurality of points at equal intervals in the positive half period of the alternating current signal through a residual current sampling circuit;
the second step is that: calculating effective values of ADC values of a plurality of points of sampling through an effective value algorithm;
the third step: and calculating the current value of the residual current signal according to the mapping relation between the real residual current signal and the effective value.
2. The method for detecting the half-wave of the residual current with high precision according to claim 1, wherein the residual current sampling circuit adopted in the first step comprises: the first switch-in end and the second switch-in end are respectively and correspondingly connected with two output signal ends of the residual current transformer, the first conversion resistor is used for converting the switched-in current signal into a voltage signal, and the first amplifier is used for amplifying the converted voltage signal;
the sampling method in the first step is to connect the output end of the first amplifier to sample signals through the ADC analog sampling port of the singlechip.
3. The half-wave detection method for the high-precision measurement of the residual current according to claim 2, wherein the first access terminal and the second access terminal are respectively connected with two ends of the first conversion resistor, one end of the first conversion resistor is connected with a non-inverting input terminal of the first amplifier, and the other end of the first conversion resistor is grounded; the output end of the first amplifier is connected with a first resistor, and the inverting input end of the first amplifier is connected with a second resistor and a third resistor in parallel; the end of the third resistor, which is far away from the end connected with the first amplifier, is grounded, and the end of the second resistor, which is far away from the inverting input end of the first amplifier, is connected with the end of the first resistor, which is connected with the first amplifier; the negative power supply end of the first amplifier is grounded, and the negative power supply end of the first amplifier is connected with one end, far away from the first amplifier, of the first resistor through a first capacitor.
4. The half-wave detection method for the high-precision measurement of the residual current according to claim 3, wherein the first access end is connected with a first TVS tube and a second capacitor in parallel; one end, far away from the first access end, of the first TVS tube is connected with the second access end; one end, far away from the first access end, of the second capacitor is connected with the second access end; and a fourth resistor is connected in series at one end of the first conversion resistor, which is far away from the first access end, and one end of the fourth resistor, which is far away from the first conversion resistor, is connected with the non-inverting input end of the first amplifier.
5. The method for detecting the half-wave of the residual current with high precision as claimed in claim 3, wherein the third step calculates the current value of the residual current signal according to the mapping relationship between the real residual current signal and the effective value by using a formula:
Xrms＝IS/Nb*R5*(R2+R3)/R3/3.3*4096；
wherein Xrms is the effective value obtained in the second step; IS IS the current value of the residual current; nb is the amplification factor of the current transformer; r5 is the first conversion resistance value; r2 is a second resistance value; r3 is the third resistance value.
6. The half-wave detection method for measuring the residual current with high precision according to any one of claims 1 to 5, characterized in that the method adopted in the first step is as follows:
equidistant sampling is carried out in a complete alternating current signal period to obtain a plurality of sampling data, signals in a positive half period are amplified through a residual current sampling circuit, signals in a negative half period are filtered, and ADC values of a plurality of points sampled at equal intervals in the positive half period of the alternating current signals are obtained.
7. The half-wave detection method for measuring the residual current with high precision according to any one of claims 1 to 5, characterized in that the effective value of the ADC values of the plurality of points sampled in the second step calculated by the effective value algorithm is as follows:
and (3) obtaining an effective value by a root mean square algorithm according to a plurality of point ADC values collected in the positive half period of the alternating current signal obtained in the first step, and then multiplying the effective value by the coefficient proportion of a hardware circuit to obtain an actual effective value.
8. A half-wave detection circuit for high-precision measurement of residual current is characterized by comprising a third access end and a fourth access end which are respectively and correspondingly connected with two output signal ends of a residual current transformer, a second conversion resistor for converting an accessed current signal into a voltage signal, and a second amplifier for amplifying the converted voltage signal; the third access end and the fourth access end are respectively connected with two ends of the second conversion resistor, one end of the second conversion resistor is connected with the non-inverting input end of the second amplifier, and the other end of the second conversion resistor is grounded;
the output end of the second amplifier is connected with a fifth resistor, and the inverting input end of the second amplifier is connected with a sixth resistor and a seventh resistor in parallel; one end of the seventh resistor, which is far away from the end connected with the second amplifier, is grounded, and one end of the sixth resistor, which is far away from the inverting input end of the second amplifier, is connected with one end of the fifth resistor, which is connected with the second amplifier; the negative power supply end of the second amplifier is grounded, and the negative power supply end of the second amplifier is connected with one end, far away from the second amplifier, of the fifth resistor through a third capacitor.
9. The half-wave detection circuit for measuring the residual current with high precision according to claim 8, wherein the third access end is connected with a second TVS tube and a fourth capacitor in parallel; one end, far away from the third access end, of the second TVS tube is connected with the fourth access end; one end, far away from the third access end, of the fourth capacitor is connected with the fourth access end; an eighth resistor is connected in series to one end, far away from the third access end, of the second conversion resistor, and one end, far away from the second conversion resistor, of the eighth resistor is connected with the non-inverting input end of the second amplifier.
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|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| CB02 | Change of applicant information |
Address after: 518000 the three floor of the new world apartment, Nanshan Avenue, Nanshan District, Shenzhen, Guangdong (for office only). Applicant after: Shenzhen hi tech investment Sanjiang Electronics Co.,Ltd. Address before: 518000 the three floor of the new world apartment, Nanshan Avenue, Nanshan District, Shenzhen, Guangdong (for office only). Applicant before: SHENZHEN FANHAI SANJIANG ELECTRONICS Co.,Ltd. |
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| CB02 | Change of applicant information |