CN108732415A - Ac sensor and breaker - Google Patents
Ac sensor and breaker Download PDFInfo
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- CN108732415A CN108732415A CN201710273387.1A CN201710273387A CN108732415A CN 108732415 A CN108732415 A CN 108732415A CN 201710273387 A CN201710273387 A CN 201710273387A CN 108732415 A CN108732415 A CN 108732415A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
- G01R15/183—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/12—Measuring rate of change
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H71/00—Details of the protective switches or relays covered by groups H01H73/00 - H01H83/00
- H01H71/10—Operating or release mechanisms
- H01H71/12—Automatic release mechanisms with or without manual release
- H01H71/123—Automatic release mechanisms with or without manual release using a solid-state trip unit
- H01H71/125—Automatic release mechanisms with or without manual release using a solid-state trip unit characterised by sensing elements, e.g. current transformers
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Abstract
A kind of ac sensor and breaker are disclosed in the embodiment of the present invention.Wherein, ac sensor includes：First detection unit is configured to be detected the exchange in setting range, obtains corresponding first exchange indicated value；Second detection unit is configured to be detected the exchange outside the setting range, obtains corresponding second exchange indicated value；And current output unit, it is configured to export the first exchange indicated value or the second exchange indicated value.Technical solution in the embodiment of the present invention can improve the frequency and amplitude measurement range of ac sensor.
Description
Technical Field
The invention relates to the field of circuits, in particular to an alternating current sensor and a circuit breaker.
Background
The current sensor generally has a certain measurement pertinence, for example, for a current sensor in a power circuit breaker, because the current characteristics of an alternating current circuit breaker and the current characteristics of a direct current circuit breaker are different, the current sensor for the alternating current circuit breaker and the current sensor for the direct current circuit breaker are designed and used independently at present.
With the continuous development of circuit breaker applications and current sensor applications, higher requirements are also put on current sensors at present. Taking an ac current sensor as an example, it is required to be able to provide higher accuracy and a wider test range of amplitude and frequency, especially in the low frequency range. For example, wind power systems require their frequency conversion domain applications to be as low as a few Hz, even 0.2Hz, etc.
Disclosure of Invention
In view of this, the present invention provides an ac sensor on one hand and a circuit breaker on the other hand, which are used to improve the frequency and amplitude measurement range of the ac sensor, so as to implement current detection for many application scenarios.
The invention provides an alternating current sensor, which comprises: a first detection unit configured to detect an ac current within a set range, and obtain a corresponding first ac current instruction value; the setting range includes: setting a low-frequency and low-current measuring range; a second detection unit configured to detect the ac current outside the set range to obtain a corresponding second ac shop indicated value; and a current output unit configured to output the first or second ac instruction value. It can be seen that, because the ac sensor in the embodiment of the present invention is provided with two detection units, each detection unit performs current detection within a certain range by using its own measurement advantage, and finally outputs a corresponding ac current indication value, the frequency and amplitude measurement range of the ac sensor is improved, so that the ac sensor can adapt to more application scenarios.
In one embodiment, the first detection unit includes: an iron core current transformer configured to measure a current alternating current of a system to be measured and output an initial alternating current indication value; a current compensation module in which compensation coefficients calculated for different frequencies of a current to be measured are stored in advance, wherein the current compensation module is configured to: the frequency information of the initial alternating current indicated value can be obtained, a corresponding compensation coefficient is determined according to the frequency information, and the initial alternating current indicated value is amplified and compensated based on the compensation coefficient to obtain a corrected alternating current indicated value; and a first analog-to-digital conversion module configured to convert the corrected ac current instruction value from an analog quantity to a digital quantity. The initial alternating current indicated value measured by the iron core current transformer in the prior art is compensated by the current compensation module, so that the alternating current indicated value meeting the requirement can be output, and the detection range of the second detection unit is supplemented.
In one embodiment, the second detection unit includes: a differential sensor configured to measure a variation with time of an alternating current to be measured and output an alternating voltage signal in a proportional relationship with the variation; and an integration section configured to integrate and restore the alternating voltage signal to obtain a second alternating current instruction value. The second detection unit may be compatible with existing sensors that measure alternating current.
The integrating means includes: an analog integration module configured to perform analog integration on the alternating voltage signal to obtain a first partial integrated signal; a second analog-to-digital conversion module configured to perform analog-to-digital conversion on the first partial integrated signal to obtain a first partial integrated value; a digital integration module configured to digitally integrate the first portion of the integrated value to obtain a second portion of the integrated value; and a data synthesis module configured to add and synthesize the first partial integrated value and the second partial integrated value to obtain a synthesized alternating current instruction value. The integral component not only can utilize the advantages of the original alternating current measuring sensor, but also can improve the defects of the original alternating current measuring sensor, thereby improving the integral reduction precision of the whole integral component.
Furthermore, the digital integration module may be further configured to: the first alternating current indicating value can be received as an initial value of the digital integration module, and the second part of the integrated value calculated by the digital integration module is subjected to offset correction by using the first alternating current indicating value, so that the accuracy of the second part of the alternating current integrating indicating value can be further improved.
The analog integration module in this embodiment may be implemented by a passive analog integration module or an active analog integration module, and the implementation method is flexible and convenient.
In one embodiment, the analog integration module comprises: the device comprises a first integrating resistor, a second integrating resistor, a first filter resistor, a second filter resistor and an integrating capacitor; one end of the first integrating resistor is connected with one output end of the differential sensor, and the other end of the first integrating resistor is connected with one end of the first filter resistor and one end of the integrating capacitor; one end of the second integrating resistor is connected with the other output end of the differential sensor, and the other end of the second integrating resistor is connected with one end of the second filter resistor and the other end of the integrating capacitor; the other end of the first filter resistor is grounded; the other end of the second filter resistor is grounded; and the two ends of the integrating capacitor are output ends of the analog integrating module. Therefore, the analog integration module can realize analog integration, and the analog integration signal can be more accurate by arranging the filter circuit.
In one embodiment, the integration section further comprises: and the signal conditioning circuit is configured to perform processing including amplification and/or filtering on the first part of the integrated value and output the processed first part of the integrated value to the second analog-to-digital conversion module. By arranging the signal conditioning circuit, the accuracy of the analog integration signal can be further improved.
In one embodiment, the signal conditioning circuit comprises: the operational amplifier comprises an operational amplifier chip, a gain resistor and a power supply circuit; two signal input ends of the operational amplifier chip are respectively connected with two output ends of the analog integration module; two voltage input ends of the operational amplifier chip are respectively connected with a power supply end of the power supply circuit; the two gain resistor connecting ends of the operational amplifier chip are respectively connected with the two ends of the gain resistor; and the signal output end of the operational amplifier chip is connected with the input end of the second analog-to-digital conversion module.
The circuit breaker in the embodiment of the present invention may include the ac sensor in any one of the above embodiments. Correspondingly, the circuit breaker in the embodiment of the invention has higher measurement precision and larger measurement range.
Drawings
The foregoing and other features and advantages of the invention will become more apparent to those skilled in the art to which the invention relates upon consideration of the following detailed description of a preferred embodiment of the invention with reference to the accompanying drawings, in which:
fig. 1 is a schematic structural diagram of an ac sensor in an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a first detecting unit according to an example of the present invention.
Fig. 3 is a schematic structural diagram of an integrating component according to an embodiment of the present invention.
Fig. 4A is a schematic diagram of an integration component when the analog integration module is a passive analog integration module according to an example of the present invention.
Fig. 4B is a schematic diagram of an integration component when the analog integration module is an active analog integration module according to an example of the present invention.
Fig. 5 is a schematic view of a partial structure of an integrating member according to an example of the present invention.
Fig. 6 is a schematic diagram showing the connection between the equivalent circuit of the differential sensor and the passive analog integration module in fig. 5 according to an example of the present invention.
Fig. 7A is a comparison graph of sampled current values for an input signal of 1Hz in an example of the present invention, using an integration component in an embodiment of the present invention, and using a prior art analog integration block alone as the integration component.
Fig. 7B is a comparison graph of sampled current values when the integrating component in the embodiment of the present invention is used and an analog integrating module alone in the prior art is used as the integrating component in the case of an input signal of 0.2Hz in one example of the present invention.
Wherein the reference numbers are as follows:
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail by referring to the following examples.
According to the invention, in order to increase the measurement range of the ac sensor, it is necessary to first analyze the existing ac current sensor: the conventional ac current sensor usually adopts Rogowski (Rogowski) coil to measure primary current, the Rogowski coil has wide frequency range, and the general design range is from 0.1Hz to 100MHz or more, so that the requirement of general broadband measurement can be met, but the Rogowski coil also belongs to one of differential sensors because the secondary output voltage signal of the Rogowski coil is the differential of the primary current signal. A corresponding integration circuit must be added if the signal proportional to the primary current is to be truly recovered. Because the passive integration circuit has better stability, the passive integration circuit is usually adopted to realize the signal integration and restoration. However, the integrating circuit has a cut-off frequency, and if the frequency of the signal passing through the integrating circuit is lower than the cut-off frequency, the amplitude of the signal is greatly attenuated. Due to the nature of the integration circuit, the cut-off frequency cannot usually be too low, e.g. some integration circuits have a cut-off frequency around 16 Hz. Thus, when the method is applied to a breaker on the generator side of a wind power system, since the frequency of the primary current flowing into the breaker may be too low, for example, several Hz, the secondary output voltage signal of the rogowski coil is inevitably attenuated by a large amount after passing through the integrating circuit, which affects the accurate measurement of the primary current, and particularly, the breaker measurement is distorted and fails when the primary current has a short-circuit fault, which is very dangerous. It can be seen that the current measurement of the current sensor using the rogowski coil is often insufficient in the case of low frequency and small current. In addition, droop characteristics and zero drift also typically exist in the low frequency range.
Therefore, the embodiment of the invention considers that a brand-new alternating current sensor is provided, and two detection units are provided, so that one detection unit at least covers the measurement range of the current alternating current sensor, and the other sensor covers the condition of low frequency and low current, so as to supplement the measurement range of the current alternating current sensor, and further improve the frequency and amplitude measurement range of the alternating current sensor.
Furthermore, for the detection unit at least covering the measurement range of the current alternating current sensor, the measurement accuracy of the detection unit can be improved by improving the current alternating current sensor and compensating the measurement result in the frequency range with the measurement error.
Fig. 1 is a schematic structural diagram of an ac sensor in an embodiment of the present invention. As shown in fig. 1, the ac sensor mainly includes: a first detecting unit 11, a second detecting unit 12 and a current output unit 13.
The first detection unit 11 is configured to detect an ac current within a set range, and obtain a corresponding first ac current instruction value. The first ac current instruction value here may be any form of value capable of indicating the magnitude of current, such as a current value or a voltage value. Wherein, the setting range includes a set low-frequency small-current measurement range, for example, the setting range may be: the frequency range is 0.2 Hz-MkHz, and the current range is 0.2 In-NIn. Wherein M and N are natural numbers less than or equal to 10, and In is the rated current of the system to be tested.
The second detection unit 12 is configured to detect the ac current outside the set range, and obtain a corresponding second ac current instruction value. The second ac current instruction value here may be any form of value capable of indicating the magnitude of the current, such as a current value or a voltage value. Wherein, the alternating current outside the set range can cover the measuring range of the current alternating current sensor, and even a larger range. For example, the frequency range may reach 100kHz, even hundreds of kHz, and the current range may reach 100kA, even hundreds of kA.
The current output unit 13 is configured to output a first alternating current instruction value detected by the first detection unit or a second alternating current instruction value detected by the second detection unit.
In one embodiment, the first detecting unit 11 and the second detecting unit 12 may simultaneously detect the current to be detected and respectively obtain corresponding ac current indication values, and the current output unit 13 may output the ac current indication value obtained by the first detecting unit 11 when the ac current indication values of the two are within a set range, and output the ac current indication value obtained by the second detecting unit 12 when the ac current indication values of the two are beyond the set range.
In the present embodiment, the setting range is determined according to the detection capability of the first detection unit 11. The first detection unit 11 may be implemented by an iron core current transformer. The following table 1 shows a data comparison between a primary current value of a system to be measured and a secondary current value measured by an iron core current transformer in a conventional example.
TABLE 1
As can be seen from table 1, when the frequency of the current to be measured is 50Hz, the primary current value and the measured secondary current value are both 1.879, and the error is-0.00998, which is close to 0. The primary current value was 1.952 at a frequency of 1Hz, the measured secondary current values were all 1.890 with an error of-3.16022, the primary current value was 1.943 at a frequency of 0.2Hz, the measured secondary current values were all 1.7264 with an error of-11.1458. That is, the output of the iron core current transformer at low frequency is also attenuated to a certain extent, i.e., the lower the frequency, the larger the current measurement error. Therefore, in the embodiment according to the present invention, it is considered that the first ac current instruction value measured by the core current transformer is amplified and compensated to some extent. For this purpose, the compensation coefficients calculated for different frequencies may be predetermined, for example, for the example in table 1, the ratio of the primary current value at different frequencies to the measured secondary current value may be used as the compensation coefficient at the corresponding frequency, that is, the compensation coefficient may be 1.879/1.879-1 for the case of 50Hz, 1.878/1.877 for the case of 20Hz, 1.952/1.890 for the case of 1Hz, 1.943/1.7264 for the case of 0.2Hz, and so on, so that the output of the current measured by the core current transformer after being multiplied and compensated by the compensation coefficient at the corresponding frequency can satisfy the measurement requirement. For example, it is possible to cover at least a set small current small frequency measurement portion, such as 0.2 Hz. Further, it is possible to cover even a current range in a normal state of the circuit breaker, for example, a measurement portion within a rated current range of the circuit breaker.
Fig. 2 shows a schematic structural diagram of the first detection unit 11 in one example of the present invention. As shown in fig. 2, the first detection unit may include: a core current transformer 111, a current compensation module 112 and an analog-to-digital conversion module 113.
Wherein the core current transformer 111 is configured to measure a present ac current of the system under test and output an initial ac current indication value.
The current compensation module 112 is configured to pre-store compensation coefficients calculated for different current frequencies of the system under test. The current compensation module 112 may further perform fourier transform on the initial ac current indicated value, obtain frequency information of the initial ac current indicated value, determine a corresponding compensation coefficient according to the frequency information, and perform amplification compensation on the initial ac current indicated value by using the compensation coefficient to obtain a corrected first ac current indicated value. The compensation coefficients calculated for different current frequencies may be stored in a table form of correspondence between the frequencies and the compensation coefficients, or in a form of a function of the relationship between the frequencies and the compensation coefficients.
In one embodiment, the compensation coefficients corresponding to different frequencies of the current to be measured may be based on a ratio of a primary current value at different frequencies to a measured secondary current value in the historical empirical values. At this time, the compensation coefficient is greater than or equal to 1. When the compensation coefficient is used to compensate the initial ac current instruction value, the compensation coefficient may be multiplied by the initial ac current instruction value to obtain a corrected ac current instruction value.
The analog-to-digital conversion module 113 is configured to convert the ac current instruction value corrected by the current compensation module 112 from an analog value to a digital value and output the converted value.
The second detecting unit 12 can be used to measure the ac current outside the measuring range of the first detecting unit 11, that is, measure the ac current that cannot be covered by the measuring range of the first detecting unit 11, for example, measure a large current, an abnormal current, an abrupt current, etc. For example, the frequency range may be up to 100kHz and the current range may be up to 100 kA. In particular implementation, the second detection unit 12 may include a differential sensor 121 and an integration part 122 as shown in fig. 3. Among them, the differential sensor 121 may be configured to measure a variation amount of a current to be measured with time and output an alternating voltage signal proportional to the variation amount of the current. The integrating part 122 may be configured to integrate and restore the ac voltage signal output from the differential sensor 121 to obtain the ac current instruction value.
The differential sensor 121 can be implemented using a Rogowski (Rogowski) coil, among other things, with high accuracy and low cost. The rogowski coil is a ring coil uniformly wound on a non-ferromagnetic material, and the output signal of the rogowski coil is the differential of current with respect to time. The rogowski coil is a hollow annular coil and can be directly sleeved on a measured conductor. The alternating current flowing in the conductor creates an alternating magnetic field around the conductor, which induces an alternating voltage signal in the coil proportional to the current change. The output voltage of the coil can be represented by formula VoutExpressed as M di/dt. Where M is the mutual inductance of the coil. di/dt is the current transformation ratio. By integrating the voltage signal output by the rogowski coil by a special integrating component, another alternating voltage signal can be obtained, and the voltage signal can accurately reproduce the waveform of the measured current signal.
The integration component 122 can be implemented by an analog integration module, a digital integration module, or a combination of the analog integration module and the digital integration module. For example, fig. 3 shows a schematic structural diagram of the integrating component 122. As shown in fig. 3, the integrating part 122 may include: an analog integration module 1221, an analog-to-digital conversion module 1222, a digital integration module 1223, and a data synthesis module 1224.
The analog integration module 1221 is configured to perform analog integration on the ac voltage signal output by the differential sensor 121 to obtain a first partially integrated signal.
The analog-to-digital conversion module 1222 is configured to analog-to-digital convert the first partially integrated signal to obtain a first partially integrated value.
The digital integration module 1223 is configured to digitally integrate the first portion of the integrated value to obtain a second portion of the integrated value.
The data synthesis module 1224 is configured to add and synthesize the first partial integrated value and the second partial integrated value, and calculate a second ac current indication value after the integral reduction.
Further, the integrating part 122 may further include: a signal conditioning circuit 1225, configured to amplify and/or filter the first partial integrated signal output by the analog integration module 1221, and output the processed first partial integrated signal to the analog-to-digital conversion module 1222.
Further, the digital integration module 1223 in the present embodiment may be further configured to use the first ac current instruction value obtained by the first detection unit 11 as an initial value of the digital integration module 1223, and perform offset correction on the second partial integrated value calculated by the digital integration module 1223 using the first ac current instruction value obtained by the first detection unit 11. Here, since the first detection unit 11 and the second detection unit 12 detect the same current, in the case where the outputs of the first detection unit 11 and the second detection unit 12 are both ensured to be effective, the output of the second detection unit 12 can be corrected by the output of the first detection unit 11, that is, the offset correction described above.
The integrating part 122 in the embodiment shown in fig. 3 is added with an analog-to-digital conversion module 1222, a digital integration module 1223 and a data synthesis module 1224, compared with the existing integrating circuit including only an analog integration module 1221. The working principle is roughly as follows: for the measurement range which can be covered by the existing analog integration module 1221 and meets the precision requirement, the output of the digital integration module 1223 can be almost ignored, so the output of the data synthesis module 1224 is basically equivalent to the output of the existing analog integration module 1221, for the measurement range which cannot be met by the existing analog integration module 1221 and meets the precision requirement, the output of the digital integration module 1223 can perform error compensation on the output of the existing analog integration module 1221, and thus the result output by the data synthesis module 1224 is equivalent to the output after the existing analog integration module 1221 is corrected, thereby improving the measurement precision of the whole integration part 122 and realizing the improvement of the problems existing in the existing alternating current sensor.
In this embodiment, the analog integration module 1221 may be a passive analog integration module or an active analog integration module.
Fig. 4A shows a schematic diagram of integrator component 122 when analog integrator module 1221 is a passive analog integrator module, and fig. 4B shows a schematic diagram of integrator component 122 when analog integrator module 1221 is an active analog integrator module. As shown in fig. 4A, the left side is a passive analog integration module, the right side is a digital integration module 1223, and the data synthesis module 1224 performs the summation and synthesis operation; as shown in fig. 4B, the left side is the active analog integration module, the right side is the digital integration module 1223, and the data synthesis module 1224 performs the summation and synthesis operation.
Accordingly, the integration principle of the integrating section 122 when the analog integrating module 1221 is a passive analog integrating module is shown in the following equation (1); the integration principle of the integrating section 122 when the analog integrating module 1221 is an active analog integrating module is shown in equation (2).
Wherein I (t) is sampling current, M is mutual inductance coefficient of Rogowski coil, RC is passive analog integration module, R is resistance value of passive analog integration module, and C is zeroThe values of the capacitance value, R and C of the source analog integration module can meet the design requirement of the known passive analog integration; riCiR0Being active analog integrating modules, RiIs the resistance value of the active analog integration module, CiFor simulating the capacitance value of the integrating module, R0Is and CiParallel resistance value, Ri、Ci、R0The value of (a) can be determined according to the requirement of satisfying the common active analog integral design; vinIs the output of the Rogowski coil as the input of the passive analog integration module; voutThe output of the passive analog integration module is simultaneously used as the input of the digital integration module; dt is the integral sign.
With the analog integration module described above, the dynamic range of the current signal may depend only on the amplitude range of the current.
With the above-described digital integration block, it is possible to integrate the output of the analog integration section, so that the output of the Rogowski coil can be sufficiently integrated to obtain a current instruction value having no droop even at a low frequency, such as 0.2 Hz.
Fig. 5 shows a schematic diagram of a part of the integrating component 122 in an example, and as shown in fig. 5, the integrating component 122 includes a passive RC-based analog integrating module 1221, which may include: the circuit comprises a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4 and a first capacitor C1.
One end of the first resistor R1 is connected to one output terminal of the differential sensor 121, and the other end is connected to one end of the third resistor R3 and one end of the first capacitor C1.
The second resistor R2 has one terminal connected to the other output terminal of the differential sensor 121 and the other terminal connected to one terminal of the fourth resistor R4 and the other terminal of the first capacitor C1.
The other end of the third resistor R3 is connected to ground.
The other end of the fourth resistor R4 is connected to ground.
The two ends of the first capacitor C1 are the output ends of the analog integration module 1221.
The first resistor R1 and the second resistor R2 are integral resistors, and the first capacitor C1 is an integral capacitor, which form the main body of the passive analog integration module. The third resistor R3 and the fourth resistor R4 are filter resistors.
Furthermore, the integrating component 122 in fig. 5 further includes a signal conditioning circuit 1225, and the signal conditioning circuit 1225 may include: operational amplifier chip U2, gain resistance R5 and power supply circuit. The gain resistor R5 may also be referred to as a fifth resistor.
Two signal input ends + IN and-IN of the operational amplifier chip U2 are respectively connected with two output ends of the analog integration module 1221.
Two voltage input ends U +, U-of the operational amplifier chip U2 are connected to the power supply end of the power supply circuit 12251, respectively.
Two gain resistor connection ends RG-RG + of the operational amplifier chip U2 are respectively connected with two ends of the gain resistor R5.
The signal output of the operational amplifier chip U2 is connected to an input of an analog-to-digital conversion module 1222.
The power supply method of the operational amplifier chip U2 in this embodiment may be: 1) a symmetrical dual power supply mode or 2) a single power supply mode.
When the symmetrical dual power supply mode is adopted, as shown in fig. 5, a positive power supply + E and a negative power supply-E opposite to the common terminal (ground) are respectively connected to the U + and U-pins of the operational amplifier. In this way, the signal source can be connected directly to the input pin of the operational amplifier chip, and the amplitude of the output voltage can reach the positive and negative symmetrical power supply voltage.
As shown in fig. 5, the power supply circuit includes: a sixth resistor R6 and a second capacitor C2 connected in series between the positive power supply + E and the common (ground), and a seventh resistor R7 and a third capacitor C3 connected in series between the negative power supply-E and the common (ground). The connection end between the sixth resistor R6 and the second capacitor C2 and the connection end between the seventh resistor R7 and the third capacitor C3 are power supply ends for connecting two voltage input ends of the operational amplifier chip U2.
In addition, the voltage output terminal REF of the operational amplifier chip U2 may be further connected to a connection terminal between the eighth resistor R8 and the fourth capacitor C4 connected in series, wherein the other terminal of the fourth capacitor C4 is connected to ground, and the other terminal of the eighth resistor R8 is a power supply terminal.
When the single power supply mode is adopted (not shown in the corresponding figure), the-VEE pin of the operational amplifier chip is connected to the ground. At this time, in order to ensure that the internal unit circuit of the operational amplifier chip has a proper static working point, a direct current potential must be added to the input end of the operational amplifier chip. At this time, the output of the operational amplifier chip is changed with the input signal on the basis of a certain direct current potential. In a static state, the output voltage of the operational amplifier chip is approximately VCC/2, and a capacitor can be connected to isolate the DC component in the output.
In fig. 5, the signal output terminal Vout of the operational amplifier chip U2 may be further connected to one end of a filter resistor R9 (which may also be referred to as a ninth resistor R9), and the other end of the filter resistor R9 is grounded.
Fig. 6 is a schematic diagram of the connection between the equivalent circuit of the differential sensor and the RC-based passive analog integration module of fig. 5 according to an example of the present invention. As shown in fig. 6, the equivalent circuit of the differential sensor may include: coil self-inductances L1 and L2, coil internal resistances R10 and R11, and a coil parasitic capacitance C5. In addition, the method can further comprise the following steps: filter capacitors C6 and C7.
The coil inductor L1 is connected in series with the coil internal resistance R10 and then connected with one end of the coil parasitic capacitor C5, and the coil inductor L2 is connected in series with the coil internal resistance R11 and then connected with the other end of the coil parasitic capacitor C5. Meanwhile, one end of the coil parasitic capacitor C5 is connected with the filter capacitor C6, the other end of the coil parasitic capacitor C5 is connected with the filter capacitor C7, and the other ends of the filter capacitors C6 and C7 are grounded.
Two ends of the coil parasitic capacitor C5 are used as the output end of the equivalent circuit of the differential sensor and are connected with the input end of the passive analog integration module. That is, one end of the coil parasitic capacitance C5 is connected to one end of the first integrating resistor R1 of the passive analog integration module, and the other end is connected to one end of the second integrating resistor R2 of the passive analog integration module.
Fig. 7A and 7B are graphs comparing sampled current values in the case of input signals of 1Hz and 0.2Hz in one example, when the integrating means in the embodiment of the present invention is used and when the analog integrating block alone in the related art is used as the integrating means.
In order to compare the accuracy of the measurement of the two, a reference current value for indicating an accurate ac indication value may be first set, the reference current value may be calculated based on the input signal Vin of the integrating part (i.e., the output signal of the rogowski coil), and the following equation (3) shows the reference ac indication value calculated by digital integration based on Vin:
where Δ T is the sampling period, M is the mutual inductance of the rogowski coil, and M is 1.0862uH in this example.
The following equation (4) shows the sampled current value when the analog integration block is used alone as the integration means:
wherein, R is 100k, C is 1040nF, and M is 1.0862 uH.
The following equation (5) shows the sampled current value when the integrating means in the embodiment of the present invention is employed:
v in the above formulae (4) and (5)outAnd (n) is an output value of the analog integration module, and the amplification factor and the offset adjustment can be specifically carried out by using an operational amplifier circuit and an offset compensation circuit so as to realize the formula.
It can be seen that in both fig. 7A and fig. 7B, the ac indication value obtained by using the integrating component in the embodiment of the present invention is relatively close to the reference current value, so that the measurement accuracy is higher than that obtained by using only the analog integrating module as the integrating component in the prior art.
In the above scheme, it can be seen that, because the ac sensor in the embodiment of the present invention is provided with two detection units, each detection unit performs current detection in a set range by using its own measurement advantage, and finally outputs a corresponding ac indication value, the measurement range of the ac sensor is improved, so that the ac sensor can adapt to more application scenarios. Besides being commonly used for a direct current breaker and an alternating current short-circuiting device, the current detection device can also be suitable for other current detection fields.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. An alternating current sensor, comprising:
a first detection unit (11) configured to detect an alternating current within a set range, and obtain a corresponding first alternating current indication value;
a second detection unit (12) configured to detect the alternating current outside the set range, and obtain a corresponding second alternating current indication value; and
a current output unit (13) configured to output the first AC instruction value or the second AC instruction value.
2. An alternating current sensor according to claim 1, characterized in that said first detection unit (11) comprises:
an iron core current transformer (111) configured to measure a present ac current of a system under test and output an initial ac current indication value;
a current compensation module (112) in which compensation coefficients calculated for different frequencies of the current to be measured are pre-stored, wherein the current compensation module is configured to:
frequency information of the initial ac current instruction value can be acquired,
determining a corresponding compensation coefficient according to the frequency information,
amplifying and compensating the initial alternating current indicated value based on the compensation coefficient to obtain a corrected alternating current indicated value; and
a first analog-to-digital conversion module (113) configured to convert the corrected AC current indication value from an analog quantity to a digital quantity.
3. An alternating current sensor according to claim 1 or 2, characterized in that the second detection unit (12) comprises:
a differential sensor (121) configured to measure a variation with time of an alternating current to be measured and output an alternating voltage signal proportional to the variation; and
an integration component (122) is configured to integrate and restore the alternating voltage signal to obtain a second alternating current indication value.
4. An alternating current sensor according to claim 3, characterized in that the integrating component (122) comprises:
an analog integration module (1221) configured to perform analog integration on the ac voltage signal to obtain a first partially integrated signal;
a second analog-to-digital conversion module (1222) configured to analog-to-digital convert the first partially integrated signal to obtain a first partially integrated value;
a digital integration module (1223) configured to digitally integrate the first portion of the integrated value to obtain a second portion of the integrated value; and
a data synthesis module (1224) configured to add and synthesize the first partial integrated value and the second partial integrated value to obtain a synthesized AC current indication value.
5. The ac sensor of claim 4, wherein the digital integration module (1223) is further configured to:
the first ac current instruction value can be received as an initial value of the digital integration module (1223), and the second partial integrated value calculated by the digital integration module (1223) is offset-corrected using the first ac current instruction value.
6. An alternating current sensor according to claim 4, characterized in that the analog integration module (1221) is a passive analog integration module or an active analog integration module.
7. The ac sensor according to claim 4, wherein the analog integration module (1221) comprises: the circuit comprises a first integrating resistor (R1), a second integrating resistor (R2), a first filter resistor (R3), a second filter resistor (R4) and an integrating capacitor (C1);
wherein one end of the first integrating resistor (R1) is connected to one output end of the differential sensor (121), and the other end is connected to one end of the first filter resistor (R3) and one end of the integrating capacitor (C1);
one end of the second integrating resistor (R2) is connected with the other output end of the differential sensor (121), and the other end of the second integrating resistor (R4) is connected with one end of the second filter resistor (R4) and the other end of the integrating capacitor (C1);
the other end of the first filter resistor (R3) is grounded;
the other end of the second filter resistor (R4) is grounded;
and two ends of the integrating capacitor (C1) are output ends of the analog integrating module (1221).
8. The ac sensor of claim 4, wherein the integrating component (122) further comprises: a signal conditioning circuit (1225) configured to perform processing, including amplification and/or filtering, on the first partial integration value and output the processed first partial integration value to a second analog-to-digital conversion module (1222).
9. The ac sensor of claim 8, wherein the signal conditioning circuit (1225) comprises: an operational amplifier chip (U2), a gain resistor (R5), and a power supply circuit; wherein,
two signal input ends of the operational amplifier chip (U2) are respectively connected with two output ends of the analog integration module (1221);
two voltage input ends of the operational amplifier chip (U2) are respectively connected with a power supply end of the power supply circuit;
two gain resistor connecting ends of the operational amplifier chip (U2) are respectively connected with two ends of the gain resistor (R5);
the signal output end of the operational amplifier chip (U2) is connected with the input end of the second analog-to-digital conversion module (1222).
10. An alternating current circuit breaker, characterized in that it comprises an alternating current sensor according to any one of claims 1 to 9.
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| CN201710273387.1A CN108732415B (en) | 2017-04-21 | 2017-04-21 | AC sensor and circuit breaker |
| DE102018202089.2A DE102018202089A1 (en) | 2017-04-21 | 2018-02-12 | AC sensor and circuit breaker |
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| CN102928800A (en) * | 2012-10-30 | 2013-02-13 | 中国西电电气股份有限公司 | Device for detecting current measurement accuracy of Rogowski coil |
| CN103235172A (en) * | 2013-04-24 | 2013-08-07 | 常熟开关制造有限公司(原常熟开关厂） | Current measuring method and measuring device |
| US20150292911A1 (en) * | 2014-04-09 | 2015-10-15 | Goodrich Corporation | State sensor systems and methods |
| CN205506900U (en) * | 2016-04-11 | 2016-08-24 | 南京工程学院 | Protection is with luo shi coil current mutual -inductor based on combination total mark |
| CN205643485U (en) * | 2016-05-25 | 2016-10-12 | 河北工业大学 | Single magnetic core complicated wave form current sensor |
| CN205826768U (en) * | 2016-06-17 | 2016-12-21 | 丰郅(上海)新能源科技有限公司 | Detection device and and its supporting Active Power Filter-APF, power quality analyzer |
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- 2017-04-21 CN CN201710273387.1A patent/CN108732415B/en active Active
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102928800A (en) * | 2012-10-30 | 2013-02-13 | 中国西电电气股份有限公司 | Device for detecting current measurement accuracy of Rogowski coil |
| CN103235172A (en) * | 2013-04-24 | 2013-08-07 | 常熟开关制造有限公司(原常熟开关厂） | Current measuring method and measuring device |
| US20150292911A1 (en) * | 2014-04-09 | 2015-10-15 | Goodrich Corporation | State sensor systems and methods |
| CN205506900U (en) * | 2016-04-11 | 2016-08-24 | 南京工程学院 | Protection is with luo shi coil current mutual -inductor based on combination total mark |
| CN205643485U (en) * | 2016-05-25 | 2016-10-12 | 河北工业大学 | Single magnetic core complicated wave form current sensor |
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