Self-calibration device and online self-calibration method of open current sensor

Abstract

The invention discloses a self-calibration device and an online self-calibration method of an open current sensor, the device comprises an open current transformer and a self-calibration system, the open current transformer comprises a first injection winding and a second injection winding which are located on one side, and a detection winding located on the other side; the self-calibration system comprises a first numerical control signal generation unit, a second numerical control signal generation unit, a first power amplification unit, a second power amplification unit, a first signal sampling unit, a second signal sampling unit, a third signal sampling unit and a self-calibration processing unit, the first numerical control signal generation unit, the first power amplification unit, the first signal sampling unit and the first injection winding form an offset circuit; the second numerical control signal generation unit, the second power amplification unit, the second signal sampling unit and the second injection winding form a calibration circuit; and the third signal sampling unit and the detection winding form a measuring circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of self-calibration of open-type current transformers, and more specifically, to a self-calibration device and an online self-calibration method of an open-type current transformer. Background Art

[0002] The sensing part of the open-type current transformer is a current transformer with an open coil and an air gap. In the 1970s, the Soviet Union proposed the design of an open-type current transformer, the purpose of which was to solve the magnetic saturation problem of closed-core current transformers. The basic principle of the open-type current transformer is to open the closed core, that is, to insert an air gap magnetic resistance in the original magnetic circuit. Since the magnetic permeability of air is much smaller than that of the core, a very small air gap can also produce a large magnetic resistance, thereby reducing the magnetic flux and ensuring that the current transformer works in the linear part of the magnetization curve. Abroad, Canada and the United States have relatively more research on open-type current transformers. The open-type current transformer designed by Eddy So ​​and David Bennett of Canada adopts a multi-core structure, and adds a shielding device, and uses a high-amplification operational amplifier to form an active compensation circuit to achieve a zero-flux current transformer with magnetomotive force compensation. At a current of 1-200A and a frequency range of 50-5000 Hz, it can reach 50×10 -6 The measurement accuracy is good. As a laboratory device, the power consumption of active compensation can be ignored. However, if it is used for online monitoring or live calibration of power systems, related issues have to be considered.

[0003] The open-type high-precision current transformer not only has high requirements for mechanical processing technology, but also has its own limitations in application. Therefore, this single-stage open-type transformer can only improve the accuracy performance of the open-type current transformer to a certain extent. Traditional open-type current transformers mainly include two solutions: air-core coils and iron-core coils. The open-type current transformer based on the iron-core coil has the characteristics of magnetic saturation characteristics, ferromagnetic resonance, small dynamic range, and narrow frequency response range. It has high accuracy and is not easily affected by the position of the measured current. However, in various actual application occasions, the influence of the test environment and the aging of the current clamp itself will cause its measurement error to increase, and the measurement accuracy in actual application cannot be guaranteed; the open-type current transformer based on the air-core coil has relatively poor ratio measurement accuracy and is easily affected by the position of the measured current, but it has the advantages of strong anti-interference ability, good linearity, high measurement bandwidth, good integration, and light weight. As the power electronics characteristics of the power system gradually become prominent, the load of the power system presents wide dynamic, fast time-varying, and strong random characteristics, requiring high-accuracy, high-bandwidth, and well-integrated standard transformers to support online monitoring, live calibration and other services.

[0004] Therefore, there is a need for an open current sensor that can be distinguished from offline self-calibration and can have an online self-calibration function when in use, so as to ensure the accuracy of the open current sensor when in use. Summary of the invention

[0005] The invention provides a self-calibration device and an online self-calibration method for an open-type current sensor, so as to solve the problem of how to perform online self-calibration on an open-type current transformer.

[0006] In order to solve the above problems, according to one aspect of the present invention, a self-calibration device for an open current sensor is provided, the device comprising: an open current transformer and a self-calibration system, the open current transformer comprising: a first injection winding and a second injection winding located on one side, and a detection winding located on the other side; the self-calibration system comprising: a first digital control signal generating unit, a second digital control signal generating unit, a first power amplifying unit, a second power amplifying unit, a first signal sampling unit, a second signal sampling unit, a third signal sampling unit and a self-calibration processing unit; the first digital control signal generating unit, the first power amplifying unit, the first signal sampling unit and the first injection winding constitute a cancellation circuit; the second digital control signal generating unit, the second power amplifying unit, the second signal sampling unit and the second injection winding constitute a calibration circuit; the third signal sampling unit and the detection winding constitute a measurement circuit; wherein, The first injection winding is used for coupling and offsetting the background current of the primary side; The second injection winding is used to couple a self-calibration current for self-calibration; The detection winding is used to couple the current injected by the circuit to be tested, the first injection winding and the second injection winding; The first digital control signal generating unit is connected to the self-calibration processing unit and the first power amplifying unit respectively, and is used to generate a first voltage signal corresponding to the offset current based on the first control command; The first power amplifying unit is connected to the first injection winding and the first signal sampling unit respectively, and is used to generate a compensation current required for compensation based on the first voltage signal; The second digital control signal generating unit is connected to the self-calibration processing unit and the second power amplification unit respectively, and is used to generate a second voltage signal corresponding to the self-calibration current based on the second control command; The second power amplifying unit is connected to the second injection winding and the second signal sampling unit respectively, and is used to generate a self-calibration current required for self-calibration based on the second voltage signal; The first signal sampling unit is connected to the self-calibration processing unit and is used to sample the current of the offset circuit to obtain the offset current; The second signal sampling unit is connected to the self-calibration processing unit and is used to sample the current of the calibration circuit to obtain the self-calibration current; The third signal sampling unit is connected to the detection winding and the self-calibration processing unit respectively, and is used to sample the measurement circuit to obtain the measurement current; The self-calibration processing unit is used to send the first control command and the second control command; to perform feedback control on the first digital control signal generating unit and the second digital control signal generating unit based on the offset current and the self-calibration current; to perform primary current offset of the open current transformer based on the measured current and the offset current; and to perform self-calibration of the open current transformer based on the measured current and the self-calibration current.

[0007] Preferably, the first signal sampling unit, the second signal sampling unit and the third signal sampling unit each comprise: an I / V conversion circuit, a signal conditioning circuit and an A / D sampling circuit connected in sequence; wherein, The I / V conversion circuit is used to convert the input current into voltage and output a voltage signal; The signal conditioning circuit is used to perform signal conditioning on the input voltage signal; The A / D sampling circuit is used to convert the conditioned voltage signal from an analog signal to a digital signal.

[0008] Preferably, the open-type current transformer to be tested is a clamp-on current transformer.

[0009] Preferably, the self-calibration processing unit performs primary current compensation of the open current transformer based on the measured current and the compensation current, including: According to the open current transformer clamping the measured circuit, the measured current i 2 , generating a counteracting current i 3 The initial value of is used to offset the line current i 1 ; By adjusting i 3 , so that i 2 When the value of decreases until it reaches 0 or is less than the preset current threshold, it is determined that the primary current compensation is completed.

[0010] Preferably, the self-calibration unit performs self-calibration of the open current transformer based on the measured current and the self-calibration current, comprising: When the line current i 1 When the magnetic field generated in the iron core is 0 or the amplitude offset is 0, an equal ampere-turn current is injected through the second injection winding of the calibration circuit; wherein the magnitude of the equal ampere-turn current is a first preset percentage of the rated current; Measure the current i of the measuring circuit at this time2 , calculate the ratio difference correction factor and phase difference correction factor of the open current transformer at this time, and determine whether the current ratio difference correction factor and phase difference correction factor meet the amplitude range and phase range; When the amplitude range and phase range are met, the ratio difference correction factor and phase difference correction factor of the open current transformer are calculated when injecting the equal ampere-turn current of other preset percentages of the rated current, and the amplitude range and phase range are judged; If all amplitudes and phases satisfy the amplitude range and phase range, it is determined that the open-type current transformer meets the accuracy requirement; otherwise, if there is an amplitude that does not satisfy the amplitude range or a phase that does not satisfy the phase range, it is determined that the open-type current transformer does not meet the accuracy requirement.

[0011] Preferably, the self-calibration unit obtains the ratio difference correction factor and the phase difference correction factor and determines the amplitude range and the phase range in the following manner: , , Among them, A 0i and are the primary current i of the measured circuit when the equal ampere-turn current is injected for the i-th time 1 The amplitude and phase of A 2i and are the current i in the circuit measured when the equal ampere-turn current is injected for the i-th time 2 The amplitude and phase of f bi and δ bi are the ratio difference and phase difference of the open-type current transformer when the equal ampere-turn current is injected for the i-th time; and They are the ratio difference limit and ratio difference correction factor of the mutual inductor under the corresponding accuracy level respectively; and are the phase difference limit and phase difference correction factor of the mutual inductor under the corresponding accuracy level respectively; n 2 To detect the number of winding turns.

[0012] Preferably, the self-calibration unit is further used for: According to all the ratio difference correction factors and phase difference correction factors, fitting is performed respectively to obtain an amplitude compensation curve and a phase compensation curve.

[0013] According to another aspect of the present invention, there is provided an online self-calibration method based on the self-calibration device of the open current sensor as described above, the method comprising: The signal sampling unit samples the measurement circuit to obtain the measurement current; The offset circuit is connected to the self-calibration device, and the self-calibration processing unit sends a first control command to the first digital control signal generating unit; A first digital control signal generating unit generates a first voltage signal corresponding to the offset current based on the first control command; The first power amplifying unit generates a compensation current required for compensation based on the first voltage signal; The first signal sampling unit samples the offset circuit to obtain the offset current; The self-calibration processing unit performs primary current offset of the open current transformer based on the offset current and the measurement current, and disconnects the offset circuit after the offset is completed; The calibration circuit is connected to the self-calibration device, and the self-calibration processing unit sends a second control command to the second digital control signal generating unit; A second digital control signal generating unit generates a second voltage signal corresponding to the self-calibration current based on the second control command; The second power amplifying unit generates a self-calibration current required for self-calibration based on the second voltage signal; The self-calibration processing unit performs self-calibration of the open-circuit current transformer based on the measurement current and the self-calibration current.

[0014] Preferably, the first signal sampling unit, the second signal sampling unit and the third signal sampling unit each comprise: an I / V conversion circuit, a signal conditioning circuit and an A / D sampling circuit connected in sequence; wherein, The input current is converted into voltage using an I / V conversion circuit, and a voltage signal is output; Using a signal conditioning circuit to condition the input voltage signal; The conditioned voltage signal is converted from an analog signal to a digital signal using an A / D sampling circuit.

[0015] Preferably, the open-type current transformer to be tested is a clamp-on current transformer.

[0016] Preferably, the self-calibration processing unit performs primary current offset of the open current transformer based on the offset current and the measurement current, including: According to the open current transformer clamping the measured circuit, the measured current i 2 , generating a counteracting current i 3 The initial value of is used to offset the line current i 1 ; By adjusting i 3 , so that i 2 When the value of decreases until it reaches 0 or is less than the preset current threshold, it is determined that the primary current compensation is completed.

[0017] Preferably, the self-calibration unit performs self-calibration of the open current transformer based on the measurement current and the self-calibration current, comprising: When the line current i 1 When the magnetic field generated in the core is 0 or the amplitude offset is 0, injecting an equal ampere-turn current of a second preset percentage of the rated current through the second injection winding of the calibration circuit; Measure the current i of the measuring circuit at this time 2 , calculate the ratio difference correction factor and phase difference correction factor of the open current transformer at this time, and determine whether the current ratio difference correction factor and phase difference correction factor meet the amplitude range and phase range; When the amplitude range and phase range are met, the ratio difference correction factor and phase difference correction factor of the open current transformer are calculated when injecting the equal ampere-turn current of other preset percentages of the rated current, and the amplitude range and phase range are judged; If all amplitudes and phases satisfy the amplitude range and phase range, it is determined that the open-type current transformer meets the accuracy requirement; otherwise, if there is an amplitude that does not satisfy the amplitude range or a phase that does not satisfy the phase range, it is determined that the open-type current transformer does not meet the accuracy requirement.

[0018] Preferably, the method uses the following method to obtain the ratio difference correction factor and the phase difference correction factor, and to determine the amplitude range and the phase range, including: , , Among them, A 0i and are the primary current i of the measured circuit when the equal ampere-turn current is injected for the i-th time 1 The amplitude and phase of A 2i and are the current i in the circuit measured when the equal ampere-turn current is injected for the i-th time 2 The amplitude and phase of f bi and δ bi are the ratio difference and phase difference of the open-type current transformer when the equal ampere-turn current is injected for the i-th time; and They are the ratio difference limit and ratio difference correction factor of the mutual inductor under the corresponding accuracy level respectively; and are the phase difference limit and phase difference correction factor of the mutual inductor under the corresponding accuracy level respectively; n 2 To detect the number of winding turns.

[0019] Preferably, the method further comprises: The self-calibration unit performs fitting according to all ratio difference correction factors and phase difference correction factors to obtain an amplitude compensation curve and a phase compensation curve.

[0020] The present invention provides a self-calibration device and an online self-calibration method for an open current sensor, the device comprising: a first injection winding, used for coupling to offset the background current on the primary side; a second injection winding, used for coupling the self-calibration current for self-calibration; a detection winding, used for coupling the current injected by the circuit to be tested, the first injection winding and the second injection winding; a first digital control signal generating unit, used for generating a first voltage signal corresponding to the offset current based on the first control command; a first power amplifying unit, used for generating the offset current required for offset based on the first voltage signal; a second digital control signal generating unit, used for generating a second voltage signal corresponding to the self-calibration current based on the second control command; a second power amplifying unit, used for generating a second voltage signal corresponding to the self-calibration current based on the first control command; a second digital control signal generating unit, used for generating a second voltage signal corresponding to the self-calibration current based on the second control command; a second power amplifying unit, used for generating a second voltage signal corresponding to the self-calibration current based on the first control command. The self-calibration current required for the two voltage signals to generate self-calibration; the first signal sampling unit is used to sample the current of the offset circuit to obtain the offset current; the second signal sampling unit is used to sample the current of the calibration circuit to obtain the self-calibration current; the third signal sampling unit is used to sample the measurement circuit to obtain the measurement current; the self-calibration processing unit is used to send the first control command and the second control command; is used to feedback control the first digital control signal generating unit and the second digital control signal generating unit based on the offset current and the self-calibration current; is used to offset the primary current of the open-type current transformer based on the measurement current and the offset current; is used to self-calibrate the open-type current transformer based on the measurement current and the self-calibration current. The present invention can efficiently realize the on-site online calibration of the open-type current transformer with high accuracy and low cost, can promote the transformation of the current transformer from periodic calibration to status evaluation and misalignment replacement, and can actively assist the innovation of online monitoring and live calibration of current transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings: Figure 1 1 is a schematic structural diagram of a self-calibration device 100 for an open current sensor according to an embodiment of the present invention; Figure 2 A structural diagram of a self-calibration device for an open current sensor according to an embodiment of the present invention; Figure 3 is a flow chart of a calibration process according to an embodiment of the present invention; Figure 4 FIG. 4 is a flow chart of a self-calibration method 400 for an open-circuit current sensor according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0023] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings. The present invention designs a high-accuracy open-type current sensor self-calibration device, and the basic working principle is: clamping the open-type current transformer to the circuit to be measured, and performing a current offset to be measured; then performing self-calibration of the open-type current transformer, calculating the ratio difference correction factor and the phase difference correction factor of the current point of 1%-120%, and fitting the amplitude compensation curve and the phase compensation curve.

[0024] Figure 1 FIG. 1 is a schematic diagram of the structure of a self-calibration device 100 for an open current sensor according to an embodiment of the present invention. Figure 1As shown, the self-calibration device of the open-circuit current sensor provided in the embodiment of the present invention can efficiently realize the on-site online calibration of the open-circuit current transformer with high accuracy and low cost, can promote the transformation of the current transformer from periodic calibration to state evaluation and misalignment replacement, and can actively assist the innovation of online monitoring and live calibration of the current transformer. The self-calibration device 100 of the open-circuit current sensor provided in the embodiment of the present invention includes: an open-circuit current transformer 101 and a self-calibration system 102. Among them, the open-circuit current transformer 101 includes: a first injection winding 1011 and a second injection winding 1012 located on one side, and a detection winding 1013 located on the other side; the self-calibration system 102 includes: a first digital control signal generating unit 1021, a second digital control signal generating unit 1022, a first power amplifying unit 1023, a second power amplifying unit 1024, a first signal sampling unit 1025, a second signal sampling unit 1026, a third signal sampling unit 1027 and a self-calibration processing unit 1028. The first digital control signal generating unit 1021, the first power amplifying unit 1023, the first signal sampling unit 1025 and the first injection winding 1011 constitute a cancellation circuit; the second digital control signal generating unit 1022, the second power amplifying unit 1024, the second signal sampling unit 1026 and the second injection winding 1012 constitute a calibration circuit; the third signal sampling unit 1027 and the detection winding 1013 constitute a measurement circuit.

[0025] Preferably, the first injection winding 1011 is used for coupling and offsetting the background current of the primary side.

[0026] Preferably, the second injection winding 1012 is used for coupling a self-calibration current for self-calibration.

[0027] Preferably, the detection winding 1013 is used to couple the current injected by the circuit to be tested, the first injection winding and the second injection winding.

[0028] Preferably, the first digital control signal generating unit 1021 is connected to the self-calibration processing unit and the first power amplification unit, respectively, and is used to generate a first voltage signal corresponding to the offset current based on the first control command.

[0029] Preferably, the first power amplifying unit 1023 is connected to the first injection winding and the first signal sampling unit, respectively, and is used to generate a compensation current required for compensation based on the first voltage signal.

[0030] Preferably, the second digital control signal generating unit 1022 is connected to the self-calibration processing unit and the second power amplification unit, respectively, and is used to generate a second voltage signal corresponding to the self-calibration current based on the second control command.

[0031] Preferably, the second power amplifying unit 1024 is connected to the second injection winding and the second signal sampling unit, respectively, and is used to generate a self-calibration current required for self-calibration based on the second voltage signal.

[0032] Preferably, the first signal sampling unit 1025 is connected to the self-calibration processing unit, and is used to sample the current of the offset circuit to obtain the offset current.

[0033] Preferably, the second signal sampling unit 1026 is connected to the self-calibration processing unit, and is used to sample the current of the calibration circuit to obtain the self-calibration current.

[0034] Preferably, the third signal sampling unit 1027 is connected to the detection winding and the self-calibration processing unit respectively, and is used to sample the measurement circuit to obtain the measurement current.

[0035] Preferably, the first signal sampling unit 1025, the second signal sampling unit 1026 and the third signal sampling unit 1027 each include: an I / V conversion circuit, a signal conditioning circuit and an A / D sampling circuit connected in sequence; wherein, The I / V conversion circuit is used to convert the input current into voltage and output a voltage signal; The signal conditioning circuit is used to perform signal conditioning on the input voltage signal; The A / D sampling circuit is used to convert the conditioned voltage signal from an analog signal to a digital signal.

[0036] Preferably, the open-type current transformer to be tested is a clamp-on current transformer.

[0037] Preferably, the self-calibration processing unit 1028 is used to send the first control command and the second control command; to perform feedback control on the first digital control signal generating unit and the second digital control signal generating unit based on the compensation current and the self-calibration current; to perform primary current compensation of the open current transformer based on the measured current and the compensation current; and to perform self-calibration of the open current transformer based on the measured current and the self-calibration current.

[0038] Combination Figure 2 As shown, in the present invention, the entire device is composed of a clamp-on transformer and a self-calibration circuit system.

[0039] The clamp-on transformer consists of a housing, an iron core in the housing, and two injection windings on the left half of the iron core (the first injection winding n 3 and the second injection winding n 4), the detection winding on the right half of the core and the "X"-shaped handle for controlling the separation of the jaws, wherein the number of turns of the injection winding is equal to the number of turns of the detection winding, and the setting position thereof can also be flexibly and variably placed on the cores on the same side of the core. The first injection winding and the second injection winding are respectively an injection winding for offset and an injection winding for self-calibration, respectively coupling the primary current for offset and the working current for self-calibration. The detection winding is used to couple the current injected by the measured line or the injection winding.

[0040] exist Figure 2 in,i 1 、i 2 、i 3 、i 4 They are the primary current to be measured, the secondary induction current, the offset current used for offset, and the self-calibration current used for self-calibration. 2 、n 3 、n 4 They are the winding turns for measurement, the injection winding turns for offset, and the injection winding turns for self-calibration. S1 and S2 are the program-controlled switches of the injection circuit for offset and the injection circuit for self-calibration, respectively.

[0041] Combination Figure 2 As shown, the self-calibration circuit system is composed of a digital control signal generating unit 1 (i.e., a first digital control signal generating unit), a digital control signal generating unit 2 (i.e., a second digital control signal generating unit), a power amplifier unit 1 (i.e., a first power amplifier unit), a power amplifier unit 2 (i.e., a second power amplifier unit), a signal sampling unit 1 (i.e., a first signal sampling unit), a signal sampling unit 2 (i.e., a second signal sampling unit), a signal sampling unit 3 (i.e., a third signal sampling unit) and a self-calibration processing unit. The power amplifier unit 1 outputs an offset current required for offset. The power amplifier unit 2 outputs a self-calibration current required for self-calibration. The digital control signal generating unit 1 and the digital control signal generating unit 2 are controlled by the self-calibration processing unit to generate voltage signals corresponding to the offset current and the self-calibration current, and output them to the power amplifier unit. The signal sampling unit is composed of an I / V conversion circuit, a signal conditioning circuit and an A / D sampling circuit. The I / V conversion circuit is used to perform I / V conversion on the current of the injection circuit and the detection circuit, and output a voltage signal. The signal conditioning circuit is used to amplify, filter, and raise the voltage of the input signal, and output a voltage signal that meets the AD sampling requirements. The A / D sampling circuit converts the input voltage signal from an analog signal to a digital signal. The signal sampling unit 1 is used to sample the injection line for offset, the signal sampling unit 2 is used to sample the injection line for self-calibration, and the signal sampling unit 3 is used to sample the measurement line for detection. The self-calibration processing unit is used to control the entire offset and self-calibration process.

[0042] Preferably, the self-calibration processing unit 1028 performs primary current compensation of the open current transformer based on the measured current and the compensation current, including: According to the open current transformer clamping the measured circuit, the measured current i 2 , generating a counteracting current i 3 The initial value of is used to offset the line current i 1 ; By adjusting i 3 , so that i 2 When the value of decreases until it reaches 0 or is less than the preset current threshold, it is determined that the primary current compensation is completed.

[0043] In the present invention, the primary current offset method of the open current transformer is: Step 1: After the open-type current transformer is clamped around the line under test, measure the i 2 .

[0044] Step 2: Self-calibration processing unit according to i 2 , generating a counteracting injection current i 3 The initial value is used to offset the background current i 1 , which can be expressed as. Among them, there is a relationship between the currents: , where ε 2 is the magnetomotive force to be offset.

[0045] Step 3: The self-calibration processing unit controls the injection current i 3 , by adjusting i 3 , so that i 2 The value decreases until it reaches 0 or is less than the threshold i A When the current is offset, the self-calibration mode is entered.

[0046] Preferably, the self-calibration unit 1028 performs self-calibration of the open current transformer based on the measured current and the self-calibration current, including: When the line current i 1 When the magnetic field generated in the iron core is 0 or the amplitude offset is 0, an equal ampere-turn current is injected through the second injection winding of the calibration circuit; wherein the magnitude of the equal ampere-turn current is a first preset percentage of the rated current; Measure the current i of the measuring circuit at this time 2 , calculate the ratio difference correction factor and phase difference correction factor of the open current transformer at this time, and determine whether the current ratio difference correction factor and phase difference correction factor meet the amplitude range and phase range; When the amplitude range and phase range are met, the ratio difference correction factor and phase difference correction factor of the open current transformer are calculated when injecting the equal ampere-turn current of other preset percentages of the rated current, and the amplitude range and phase range are judged; If all amplitudes and phases satisfy the amplitude range and phase range, it is determined that the open-type current transformer meets the accuracy requirement; otherwise, if there is an amplitude that does not satisfy the amplitude range or a phase that does not satisfy the phase range, it is determined that the open-type current transformer does not meet the accuracy requirement.

[0047] Preferably, the self-calibration unit 1028 obtains the ratio difference correction factor and the phase difference correction factor and determines the amplitude range and the phase range in the following manner: , , Among them, A 0i and are the primary current i of the measured circuit when the equal ampere-turn current is injected for the i-th time 1 The amplitude and phase of A 2i and are the current i in the circuit measured when the equal ampere-turn current is injected for the i-th time 2 The amplitude and phase of f bi and δ bi are the ratio difference and phase difference of the open-type current transformer when the equal ampere-turn current is injected for the i-th time; and They are the ratio difference limit and ratio difference correction factor of the mutual inductor under the corresponding accuracy level respectively; and are the phase difference limit and phase difference correction factor of the mutual inductor under the corresponding accuracy level respectively; n 2 To detect the number of winding turns.

[0048] In the present invention, the method for self-calibration of an open current transformer is: Step 1: When the measured line i 1 When the magnetic field generated in the core is 0 or the amplitude is offset to 0, i 4 Inject a current equal to 1% of the rated current and measure the corresponding i 2 Electric current.

[0049] Step 2, calculate the ratio difference correction factor and phase difference correction factor of the open current transformer at this time, and determine whether the current ratio difference correction factor and phase difference correction factor meet the amplitude range and phase range. 1 The amplitude is A 0 , the phase is φ 0, and the measured 2 The amplitude is A 2 , the phase is φ 2 At this time, the ratio difference correction factor and the phase difference correction factor can be obtained by the following methods, and the amplitude range and the phase range can be determined, including: , , Among them, A 0i and are the primary current i of the measured circuit when the equal ampere-turn current is injected for the i-th time 1 The amplitude and phase of A 2i and are the current i in the circuit measured when the equal ampere-turn current is injected for the i-th time 2 The amplitude and phase of f bi and δ bi are the ratio difference and phase difference of the open-type current transformer when the equal ampere-turn current is injected for the i-th time; and They are the ratio difference limit and ratio difference correction factor of the mutual inductor under the corresponding accuracy level respectively; and are the phase difference limit and phase difference correction factor of the mutual inductor under the corresponding accuracy level respectively; n 2 To detect the number of winding turns.

[0050] Step 3: If the ratio difference correction factor and the phase difference correction factor meet the amplitude range and the phase range when the equal ampere-turn current of 1% of the rated current is injected, the ratio difference correction factor and the phase difference correction factor at 5%, 20%, 100%, and 120% are measured and calculated respectively according to the above steps, and the amplitude range and the phase range are judged respectively. Among them, in the present invention, when the equal ampere-turn current of different percentages of the rated current is injected, the corresponding amplitude range and the phase range are different.

[0051] Step 4: If all amplitudes and phases satisfy the amplitude range and phase range, it is determined that the open-type current transformer meets the accuracy requirement; otherwise, if there is an amplitude that does not satisfy the amplitude range or a phase that does not satisfy the phase range, it is determined that the open-type current transformer does not meet the accuracy requirement.

[0052] Preferably, the self-calibration unit 1028 is further used for: According to all the ratio difference correction factors and phase difference correction factors, fitting is performed respectively to obtain an amplitude compensation curve and a phase compensation curve.

[0053] In the present invention, the ratio difference correction factors and phase difference correction factors of calibration points such as 1%, 5%, 20%, 100%, and 120% can be fitted respectively (the fitting method can adopt polynomial fitting, but is not limited to polynomial fitting), and the amplitude compensation curve and the phase compensation curve can be fitted and stored in the self-calibration unit for compensation of non-calibration points.

[0054] Specifically, combined Figure 3 As shown in the figure, the self-calibration process of the open-type current transformer includes: Step 1: Clamp the open current transformer to the circuit to be tested and proceed to the next step; Step 2: Measure i 2 If i 2 If i2 is 0, go to step 4; if i2 is not 0, go to the next step; Step 3: Close the "control switch (S1)" to start the current offset function of the circuit to be tested. When the current offset function is completed, proceed to the next step; Step 4: Close the "control switch (S2)", start self-calibration, set the calibration current point (including 1%, 5%, 20%, 100%, 120% of the rated current), and proceed to the next step; Step 5: According to the set calibration current point, the self-calibration processing unit controls the digital control signal generating unit to generate a self-calibration signal and enter the next step; Step 6: Collect the signals of the injection winding and the detection winding and proceed to the next step; Step 7: The self-calibration processing unit processes the collected injection winding signal and detection signal data, calculates the ratio difference correction factor and the phase difference correction factor, and performs range judgment; if the judgment result is that the ratio difference correction factor and the phase difference correction factor meet the amplitude range and the phase range, proceed to the next step; otherwise, it is directly determined that the open current transformer does not meet the accuracy requirements and needs to be repaired, and the self-calibration process ends; Step 8: Determine whether all self-calibration current points have completed self-calibration. If completed, proceed to the next step. If not completed, proceed to step 4 to set the next calibration current point. Step 9: If all amplitudes and phases meet the amplitude range and phase range, it is determined that the open current transformer meets the accuracy requirement; Step 10, fitting the amplitude and phase compensation curve, and storing it in the self-calibration processing unit.

[0055] Figure 4 FIG. 4 is a flow chart of a self-calibration method 400 for an open current sensor according to an embodiment of the present invention. Figure 4As shown, an online self-calibration method 400 based on the self-calibration device of the open current sensor as described above provided in an embodiment of the present invention starts from step 401. In step 401, a signal sampling unit samples a measurement circuit to obtain a measurement current.

[0056] In step 402, the cancellation circuit is connected to the self-calibration device, and the self-calibration processing unit sends a first control command to the first digital control signal generating unit.

[0057] In step 403 , a first digital control signal generating unit generates a first voltage signal corresponding to the offset current based on the first control command.

[0058] In step 404, the first power amplifying unit generates a cancellation current required for cancellation based on the first voltage signal.

[0059] In step 405 , the first signal sampling unit samples the offset circuit to obtain the offset current.

[0060] In step 406, the self-calibration processing unit performs primary current cancellation of the open current transformer based on the cancellation current and the measured current, and disconnects the cancellation circuit after the cancellation is completed.

[0061] In step 407, the calibration circuit is connected to the self-calibration device, and the self-calibration processing unit sends a second control command to the second digital control signal generating unit.

[0062] In step 408 , the second digital control signal generating unit generates a second voltage signal corresponding to the self-calibration current based on the second control command.

[0063] In step 409 , the second power amplifying unit generates a self-calibration current required for self-calibration based on the second voltage signal.

[0064] In step 410, the self-calibration processing unit performs self-calibration of the open-circuit current transformer based on the measured current and the self-calibration current.

[0065] Preferably, the first signal sampling unit, the second signal sampling unit and the third signal sampling unit each comprise: an I / V conversion circuit, a signal conditioning circuit and an A / D sampling circuit connected in sequence; wherein, The input current is converted into voltage using an I / V conversion circuit, and a voltage signal is output; Using a signal conditioning circuit to condition the input voltage signal; The conditioned voltage signal is converted from an analog signal to a digital signal using an A / D sampling circuit.

[0066] Preferably, the open-type current transformer to be tested is a clamp-on current transformer.

[0067] Preferably, the self-calibration processing unit performs primary current offset of the open current transformer based on the offset current and the measurement current, including: According to the open current transformer clamping the measured circuit, the measured current i 2 , generating a counteracting current i 3 The initial value of is used to offset the line current i 1 ; By adjusting i 3 , so that i 2 When the value of decreases until it reaches 0 or is less than the preset current threshold, it is determined that the primary current compensation is completed.

[0068] Preferably, the self-calibration unit performs self-calibration of the open current transformer based on the measurement current and the self-calibration current, comprising: When the line current i 1 When the magnetic field generated in the iron core is 0 or the amplitude offset is 0, an equal ampere-turn current is injected through the second injection winding of the calibration circuit; wherein the magnitude of the equal ampere-turn current is a first preset percentage of the rated current; Measure the current i of the measuring circuit at this time 2 , calculate the ratio difference correction factor and phase difference correction factor of the open current transformer at this time, and determine whether the current ratio difference correction factor and phase difference correction factor meet the amplitude range and phase range; When the amplitude range and phase range are met, the ratio difference correction factor and phase difference correction factor of the open current transformer are calculated when injecting the equal ampere-turn current of other preset percentages of the rated current, and the amplitude range and phase range are judged; If all amplitudes and phases satisfy the amplitude range and phase range, it is determined that the open-type current transformer meets the accuracy requirement; otherwise, if there is an amplitude that does not satisfy the amplitude range or a phase that does not satisfy the phase range, it is determined that the open-type current transformer does not meet the accuracy requirement.

[0069] Preferably, the method uses the following method to obtain the ratio difference correction factor and the phase difference correction factor, and to determine the amplitude range and the phase range, including: , , Among them, A 0i and are the primary current i of the measured circuit when the equal ampere-turn current is injected for the i-th time 1 The amplitude and phase of A 2i and are the current i in the circuit measured when the equal ampere-turn current is injected for the i-th time 2 The amplitude and phase off bi and δ bi are the ratio difference and phase difference of the open-type current transformer when the equal ampere-turn current is injected for the i-th time; and They are the ratio difference limit and ratio difference correction factor of the mutual inductor under the corresponding accuracy level respectively; and are the phase difference limit and phase difference correction factor of the mutual inductor under the corresponding accuracy level respectively; n 2 To detect the number of winding turns.

[0070] Preferably, the method further comprises: The self-calibration unit performs fitting according to all ratio difference correction factors and phase difference correction factors to obtain an amplitude compensation curve and a phase compensation curve.

[0071] The self-calibration method 400 of an open-circuit current sensor according to an embodiment of the present invention corresponds to the self-calibration device 100 of an open-circuit current sensor according to another embodiment of the present invention, and will not be described in detail herein.

[0072] The present invention has been described with reference to a few embodiments. However, it is known to those skilled in the art that other embodiments than the one disclosed above are equally within the scope of the present invention.

[0073] Generally, all terms used in the present invention are interpreted according to their ordinary meaning in the technical field, unless otherwise explicitly defined therein. All references to "a / said / the [device, component, etc.]" are open to interpretation as at least one instance of the device, component, etc., unless otherwise explicitly stated. The steps of any method disclosed herein do not necessarily have to be performed in the exact order disclosed, unless explicitly stated.

[0074] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0075] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0076] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0077] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A self-calibration device for an open current sensor, characterized in that: The device comprises: an open current transformer and a self-calibration system, wherein the open current transformer comprises: a first injection winding and a second injection winding located on one side, and a detection winding located on the other side; the self-calibration system comprises: a first digital control signal generating unit, a second digital control signal generating unit, a first power amplifying unit, a second power amplifying unit, a first signal sampling unit, a second signal sampling unit, a third signal sampling unit and a self-calibration processing unit; the first digital control signal generating unit, the first power amplifying unit, the first signal sampling unit and the first injection winding constitute a cancellation circuit; the second digital control signal generating unit, the second power amplifying unit, the second signal sampling unit and the second injection winding constitute a calibration circuit; the third signal sampling unit and the detection winding constitute a measurement circuit; wherein, The first injection winding is used for coupling and offsetting the background current of the primary side; The second injection winding is used to couple a self-calibration current for self-calibration; The detection winding is used to couple the current injected by the circuit to be tested, the first injection winding and the second injection winding; The first digital control signal generating unit is connected to the self-calibration processing unit and the first power amplifying unit respectively, and is used to generate a first voltage signal corresponding to the offset current based on the first control command; The first power amplifying unit is connected to the first injection winding and the first signal sampling unit respectively, and is used to generate a compensation current required for compensation based on the first voltage signal; The second digital control signal generating unit is connected to the self-calibration processing unit and the second power amplification unit respectively, and is used to generate a second voltage signal corresponding to the self-calibration current based on the second control command; The second power amplifying unit is connected to the second injection winding and the second signal sampling unit respectively, and is used to generate a self-calibration current required for self-calibration based on the second voltage signal; The first signal sampling unit is connected to the self-calibration processing unit and is used to sample the current of the offset circuit to obtain the offset current; The second signal sampling unit is connected to the self-calibration processing unit and is used to sample the current of the calibration circuit to obtain the self-calibration current; The third signal sampling unit is connected to the detection winding and the self-calibration processing unit respectively, and is used to sample the measurement circuit to obtain the measurement current; The self-calibration processing unit is used to send the first control command and the second control command; to perform feedback control on the first digital control signal generating unit and the second digital control signal generating unit based on the offset current and the self-calibration current; to perform primary current offset of the open current transformer based on the measured current and the offset current; and to perform self-calibration of the open current transformer based on the measured current and the self-calibration current.

2. The device according to claim 1, characterized in that The first signal sampling unit, the second signal sampling unit and the third signal sampling unit all include: an I / V conversion circuit, a signal conditioning circuit and an A / D sampling circuit connected in sequence; wherein, The I / V conversion circuit is used to convert the input current into voltage and output a voltage signal; The signal conditioning circuit is used to perform signal conditioning on the input voltage signal; The A / D sampling circuit is used to convert the conditioned voltage signal from an analog signal to a digital signal.

3. The device according to claim 1, characterized in that The open-type current transformer to be tested is a clamp-on current transformer.

4. The device according to claim 1, characterized in that The self-calibration processing unit performs primary current compensation of the open current transformer based on the measured current and the compensation current, including: According to the measured current i2 of the measuring circuit after the open current transformer clamps the measured line, an initial value of the offset current i3 is generated to offset the line current i1; By adjusting i3 so that the value of i2 decreases until it reaches 0 or is less than a preset current threshold, it is determined that the primary current compensation is completed.

5. The device according to claim 1, characterized in that The self-calibration unit performs self-calibration of the open current transformer based on the measurement current and the self-calibration current, comprising: When the magnetic field generated by the line current i1 on the measured line in the iron core is 0 or the amplitude is offset to 0, an equal ampere-turn current is injected through the second injection winding of the calibration circuit; wherein the magnitude of the equal ampere-turn current is a first preset percentage of the rated current; Measure the measurement current i2 of the measurement circuit at this time, calculate the ratio difference correction factor and the phase difference correction factor of the open current transformer at this time, and determine whether the current ratio difference correction factor and the phase difference correction factor meet the amplitude range and the phase range; When the amplitude range and phase range are met, the ratio difference correction factor and phase difference correction factor of the open current transformer are calculated when injecting the equal ampere-turn current of other preset percentages of the rated current, and the amplitude range and phase range are judged; If all amplitudes and phases satisfy the amplitude range and phase range, it is determined that the open-type current transformer meets the accuracy requirement; otherwise, if there is an amplitude that does not satisfy the amplitude range or a phase that does not satisfy the phase range, it is determined that the open-type current transformer does not meet the accuracy requirement.

6. The device according to claim 5, characterized in that The self-calibration unit obtains the ratio difference correction factor and the phase difference correction factor and determines the amplitude range and the phase range in the following manner: ， ， Among them, A 0i and are the amplitude and phase of the primary current i1 of the measured circuit when the equal ampere-turn current is injected for the i-th time; A 2i and are respectively the amplitude and phase of the current i2 in the measuring circuit when the equal ampere-turn current is injected for the i-th time; f bi and δ bi are the ratio difference and phase difference of the open-type current transformer when the equal ampere-turn current is injected for the i-th time; and They are the ratio difference limit and ratio difference correction factor of the mutual inductor under the corresponding accuracy level respectively; and They are the phase difference limit and phase difference correction factor of the transformer under the corresponding accuracy level; n2 is the number of turns of the detection winding.

7. The device according to claim 5, characterized in that The self-calibration unit is further used for: According to all the ratio difference correction factors and phase difference correction factors, fitting is performed respectively to obtain an amplitude compensation curve and a phase compensation curve.

8. An online self-calibration method for a self-calibration device of an open current sensor according to any one of claims 1 to 7, characterized in that: The method comprises: The signal sampling unit samples the measurement circuit to obtain the measurement current; The offset circuit is connected to the self-calibration device, and the self-calibration processing unit sends a first control command to the first digital control signal generating unit; A first digital control signal generating unit generates a first voltage signal corresponding to the offset current based on the first control command; The first power amplifying unit generates a compensation current required for compensation based on the first voltage signal; The first signal sampling unit samples the offset circuit to obtain the offset current; The self-calibration processing unit performs primary current offset of the open current transformer based on the offset current and the measurement current, and disconnects the offset circuit after the offset is completed; The calibration circuit is connected to the self-calibration device, and the self-calibration processing unit sends a second control command to the second digital control signal generating unit; A second digital control signal generating unit generates a second voltage signal corresponding to the self-calibration current based on the second control command; The second power amplifying unit generates a self-calibration current required for self-calibration based on the second voltage signal; The self-calibration processing unit performs self-calibration of the open-circuit current transformer based on the measurement current and the self-calibration current.

9. The method according to claim 8, characterized in that The first signal sampling unit, the second signal sampling unit and the third signal sampling unit all include: an I / V conversion circuit, a signal conditioning circuit and an A / D sampling circuit connected in sequence; wherein, The input current is converted into voltage using an I / V conversion circuit, and a voltage signal is output; Using a signal conditioning circuit to condition the input voltage signal; The conditioned voltage signal is converted from an analog signal to a digital signal using an A / D sampling circuit.

10. The method according to claim 8, characterized in that The open-type current transformer to be tested is a clamp-on current transformer.

11. The method according to claim 8, characterized in that The self-calibration processing unit performs primary current offset of the open current transformer based on the offset current and the measurement current, including: According to the measured current i2 of the measuring circuit after the open current transformer clamps the measured line, an initial value of the offset current i3 is generated to offset the line current i1; By adjusting i3 so that the value of i2 decreases until it reaches 0 or is less than a preset current threshold, it is determined that the primary current compensation is completed.

12. The method according to claim 8, characterized in that The self-calibration unit performs self-calibration of the open-type current transformer based on the measurement current and the self-calibration current, including: When the magnetic field generated by the line current i1 on the measured line in the iron core is 0 or the amplitude is offset to 0, an equal ampere-turn current is injected through the second injection winding of the calibration circuit; wherein the magnitude of the equal ampere-turn current is a first preset percentage of the rated current; Measure the measurement current i2 of the measurement circuit at this time, calculate the ratio difference correction factor and the phase difference correction factor of the open current transformer at this time, and determine whether the current ratio difference correction factor and the phase difference correction factor meet the amplitude range and the phase range; When the amplitude range and phase range are met, the ratio difference correction factor and phase difference correction factor of the open current transformer are calculated when injecting the equal ampere-turn current of other preset percentages of the rated current, and the amplitude range and phase range are judged; If all amplitudes and phases satisfy the amplitude range and phase range, it is determined that the open-type current transformer meets the accuracy requirement; otherwise, if there is an amplitude that does not satisfy the amplitude range or a phase that does not satisfy the phase range, it is determined that the open-type current transformer does not meet the accuracy requirement.

13. The method according to claim 12, characterized in that The method uses the following method to obtain the ratio difference correction factor and the phase difference correction factor, and to determine the amplitude range and the phase range, including: ， ， Among them, A 0i and are the amplitude and phase of the primary current i1 of the measured circuit when the equal ampere-turn current is injected for the i-th time; A 2i and are respectively the amplitude and phase of the current i2 in the measuring circuit when the equal ampere-turn current is injected for the i-th time; f bi and δ bi are the ratio difference and phase difference of the open-type current transformer when the equal ampere-turn current is injected for the i-th time; and They are the ratio difference limit and ratio difference correction factor of the mutual inductor under the corresponding accuracy level respectively; and They are the phase difference limit and phase difference correction factor of the transformer under the corresponding accuracy level; n2 is the number of turns of the detection winding.

14. The method according to claim 12, characterized in that The method further comprises: The self-calibration unit performs fitting according to all ratio difference correction factors and phase difference correction factors to obtain an amplitude compensation curve and a phase compensation curve.

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