Direct current measurement method, system, medium and equipment

Abstract

A direct current measurement method, system, medium and equipment, in the method, a switching device and a primary winding of a current transformer are connected in parallel, a control system of the switching device is arranged to monitor a current signal in a secondary winding of the current transformer in real time, and the control system controls the switching device to act at an alternating current zero crossing point moment of the primary winding; the switch device is controlled to trigger the action when the alternating current of the primary winding of the current transformer crosses the zero point, so that the switch device is switched off after being closed for a period; a current abrupt change signal is detected; when the switch device is switched off, the current abrupt change characteristic in the secondary winding of the current transformer is measured; the current abrupt change characteristics are analyzed through a signal processing algorithm to obtain an analysis result, a direct current component is calculated, the amplitude and direction of the direct current component in the primary winding are determined according to the analysis result, and therefore direct current measurement is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of current measurement in power systems, and in particular to a direct current measurement method, system, medium and equipment. Background Art

[0002] The phenomenon of DC magnetic bias in power systems, caused by the natural environment, abnormalities in power equipment, or human factors, has become a major research topic affecting the stable operation of power grids. The presence of DC current increases the magnetizing current amplitude of current transformers and causes distortion, thereby reducing measurement accuracy. In severe cases, it can even cause distribution transformers to overload or shut down, leading to serious consequences. Therefore, accurately measuring the DC current component in power systems is crucial for preventing equipment damage, ensuring safe grid operation, and optimizing grid dispatch.

[0003] Currently, DC current measurement primarily relies on devices such as Hall sensors, optical current sensors, and magnetoresistive current sensors. While these technologies offer high measurement accuracy in laboratory environments, they still face numerous limitations in practical applications, such as insufficient sensitivity, high power consumption, significant hysteresis effects, susceptibility to temperature changes, and DC offset drift. Furthermore, these devices are often sensitive to environmental noise, are bulky, and expensive, making them difficult to deploy on a large scale in power grids. Conventional current transformers, widely used in power grids, are primarily designed for measuring AC current and cannot directly measure DC current. This limitation highlights the urgent need to develop novel DC current measurement methods. Therefore, a new method that can accurately measure DC current while being low-cost, easy to install, and highly applicable is urgently needed to support the efficient monitoring and operation of power systems.

[0004] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the Invention

[0005] The present invention provides a direct current measurement method, system, medium and equipment. The method addresses the problems of insufficient sensitivity, high power consumption, poor environmental adaptability and inability to be deployed on a large scale in the prior art for direct current measurement. The method solves the technical difficulty that the existing electromagnetic induction current transformer cannot measure the direct current component, and meets the actual demand for low-cost, high-reliability measurement technology in China.

[0006] A direct current measurement method includes:

[0007] Connect the switchgear in parallel with the primary winding of the current transformer,

[0008] A control system for the switch device is set up to monitor the current signal in the secondary winding of the current transformer in real time. The control system controls the switch device to operate when the primary winding AC current crosses the zero point and adjusts the control parameters.

[0009] The switch device is triggered synchronously to operate, and the switch device is controlled to trigger when the AC current of the primary winding of the current transformer passes through the zero point, so that the switch device is closed for one cycle and then opened.

[0010] Detect the current mutation signal. When the switch device is disconnected, measure the current mutation characteristics in the secondary winding of the current transformer. Analyze the current mutation characteristics through signal processing algorithms to obtain analysis results.

[0011] The DC current component is calculated, and the amplitude and direction of the DC current component in the primary winding are determined according to the analysis result, thereby achieving measurement of the DC current.

[0012] In the DC current measurement method, the current transformer includes an electromagnetic induction AC current transformer that senses AC current.

[0013] In the DC current measurement method, the switching device includes a relay or a semiconductor switch.

[0014] In the DC current measurement method, when the current in the primary winding of the current transformer contains a DC current component, the action of the switching device causes the current in the secondary winding of the current transformer to suddenly change.

[0015] In the DC current measurement method, the current mutation characteristics include step-type mutation and pulse-type mutation.

[0016] In the DC current measurement method, peak value detection is used to extract and analyze the current mutation characteristics.

[0017] In the DC current measurement method, the step change of the current in the secondary winding is in direct proportion to the DC current value in the primary winding.

[0018] A system for implementing the method includes:

[0019] a current transformer comprising a primary winding,

[0020] a switching device connected in parallel with the primary winding,

[0021] A control system is connected to and controls the switch device to monitor the current signal in the secondary winding of the current transformer in real time. The control system controls the switch device to operate when the primary winding AC current crosses zero and adjusts the control parameters.

[0022] The trigger module is used to synchronously trigger the action of the switch device, controlling the switch device to trigger the action when the AC current of the primary winding of the current transformer passes through the zero point, so that the switch device closes for one cycle and then opens.

[0023] The detection module is used to detect the current mutation signal. When the switch device is disconnected, the current mutation characteristics in the secondary winding of the current transformer are measured, and the current mutation characteristics are analyzed by the signal processing algorithm to obtain the analysis results.

[0024] The measuring module is used to calculate the DC current component and determine the amplitude and direction of the DC current component in the primary winding according to the analysis result, thereby realizing the measurement of the DC current.

[0025] A computer storage medium includes computer instructions, which, when executed on a computer, cause the computer to execute the method described above.

[0026] An electronic device, comprising:

[0027] A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein:

[0028] When the processor executes the program, the method described is implemented.

[0029] Compared with the prior art, the present invention has the following advantages: the present invention overcomes the limitation of the existing current transformer that it cannot measure DC current through the current transformer and switch combination device; the switch device is easy to install, and the existing current transformer in the power grid can be directly used for measurement; the installation does not require additional modification of the current transformer or the addition of auxiliary windings, which reduces the cost of measuring DC current; the switch and the current transformer are in parallel, and the operation of the switch will not increase the insulation risk of the current transformer, nor will it cause additional impact on the conduction of the primary winding of the current transformer; the measurement of DC current is not affected by the magnitude of the AC current in the primary winding of the current transformer; the ability of the current transformer to measure AC current is retained, and the normal operation of the power system is not affected. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are intended only to illustrate preferred embodiments and are not to be construed as limiting the present invention. It should be understood that the drawings described below are merely examples of the present invention, and that those skilled in the art will be able to derive other drawings from these drawings without inventive effort. Throughout the drawings, identical reference numerals are used to denote identical components.

[0031] In the attached figure:

[0032] Figure 1 Schematic diagram of an equivalent circuit for implementing the method of the present invention, wherein R is a small resistance on the secondary side of the current transformer;

[0033] Figure 2 Schematic diagram of the current change in the secondary winding when the switch device is disconnected, when the DC current in the primary winding of the current transformer is in the positive direction relative to the switch branch;

[0034] Figure 3 Schematic diagram of the proportional relationship between the DC current in the primary winding of the current transformer and the current mutation value measured in the secondary winding;

[0035] Figure 4 Schematic diagram of the current change in the secondary winding when the switch device is disconnected, when the DC current in the primary winding of the current transformer is in the opposite direction relative to the switch branch;

[0036] Figure 5 Schematic diagram of the current change in the secondary winding when the switch device is disconnected when there is no DC current in the primary winding of the current transformer and only AC current exists;

[0037] Figure 6 This is a schematic diagram of the current change in the secondary winding when the switching device is disconnected when there is no AC current in the primary winding of the current transformer and only DC current exists.

[0038] The present invention will be further explained below with reference to the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0039] Specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0040] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the invention. The scope of protection of the present invention shall be as defined in the attached claims.

[0041] To facilitate understanding of the embodiments of the present invention, further explanation will be given below using specific embodiments as examples in conjunction with the accompanying drawings, and the accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0042] like Figures 1 to 6 As shown, the DC current measurement method includes the following steps:

[0043] Connect the switchgear in parallel with the primary winding of the current transformer,

[0044] A control system for the switch device is set up to monitor the current signal in the secondary winding of the current transformer in real time. The control system controls the switch device to operate when the primary winding AC current crosses the zero point and adjusts the control parameters.

[0045] The switch device is triggered synchronously to operate, and the switch device is controlled to trigger the operation when the AC current of the primary winding of the current transformer passes through the zero point, so that the switch device is closed for one cycle and then opened.

[0046] This method detects current mutation signals. When a switch device opens, the current mutation characteristics in the secondary winding of the current transformer are measured. Using a time-domain differential-based mutation detection algorithm and signal processing, the mutation characteristics are analyzed to obtain the instantaneous amplitude change. The DC current component on the primary side is then calculated. Based on the positive or negative direction of the current mutation value, the amplitude and direction of the DC current component in the primary winding are further determined, thereby enabling DC current measurement. By controlling the switching state at the AC zero-crossing time node, accurate DC current measurement in the AC power grid is achieved. When DC current is present in the system, the switching action triggers a change in the DC magnetic flux of the current transformer, causing a sudden change in the current in the secondary winding of the current transformer. By analyzing this mutation signal, the DC current amplitude in the primary winding can be accurately measured. This method utilizes a simple intelligent device, offering significant advantages such as easy installation, low cost, and compact structure. Importantly, the device does not interfere with the normal operation and metering of the AC power system during operation, ensuring system stability and security.

[0047] In a preferred embodiment of the DC current measurement method, the current transformer includes an electromagnetic induction AC current transformer that senses AC current.

[0048] In a preferred implementation of the DC current measurement method, the switching device includes a relay or a semiconductor switch.

[0049] In a preferred embodiment of the DC current measurement method, when the current in the primary winding of the current transformer contains a DC current component, the operation of the switching device causes the current in the secondary winding of the current transformer to suddenly change.

[0050] In a preferred embodiment of the direct current measurement method, the current mutation characteristics include step-type mutation and pulse-type mutation.

[0051] In a preferred embodiment of the DC current measurement method, peak value detection is used to extract and analyze the current mutation characteristics.

[0052] In a preferred embodiment of the DC current measurement method, the step change of the current in the secondary winding is in direct proportion to the DC current value in the primary winding.

[0053] A system for implementing the method includes:

[0054] a current transformer comprising a primary winding,

[0055] a switching device connected in parallel with the primary winding,

[0056] A control system is connected to and controls the switch device to monitor the current signal in the secondary winding of the current transformer in real time. The control system controls the switch device to operate when the primary winding AC current crosses zero and adjusts the control parameters.

[0057] The trigger module is used to synchronously trigger the action of the switch device, controlling the switch device to trigger the action when the AC current of the primary winding of the current transformer passes through the zero point, so that the switch device closes for one cycle and then opens.

[0058] The detection module is used to detect the current mutation signal. When the switch device is disconnected, the current mutation characteristics in the secondary winding of the current transformer are measured, and the current mutation characteristics are analyzed by the signal processing algorithm to obtain the analysis results.

[0059] The measuring module is used to calculate the DC current component and determine the amplitude and direction of the DC current component in the primary winding according to the analysis result, thereby realizing the measurement of the DC current.

[0060] A computer storage medium includes computer instructions, which, when executed on a computer, cause the computer to execute the method described above.

[0061] An electronic device, comprising:

[0062] A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein:

[0063] When the processor executes the program, the method described is implemented.

[0064] In one embodiment, the method comprises the following steps:

[0065] Connect the switch device in parallel with the primary winding of the current transformer, and ensure that the connection between the switch and the current transformer has low resistance and low loss characteristics to ensure the accuracy of signal transmission;

[0066] A control system for the switchgear is provided, the control system being used to accurately monitor the current signal in the secondary winding of the current transformer and adjust the control parameters as needed;

[0067] The control switch device triggers the switch action when the AC current of the primary winding of the current transformer passes through the zero point, closes for one cycle and then opens, ensuring the precise synchronization of the switch action and the AC current zero point, avoiding inaccurate measurement due to time delay or error;

[0068] Measure the sudden change of current in the secondary winding of the current transformer when the switch is opened and closed, and analyze the characteristics of the current sudden change, including step-type sudden change and pulse-type sudden change, through signal processing algorithm;

[0069] Based on the analysis results of the sudden change signal, the amplitude and direction of the DC current component in the primary winding are determined. Furthermore, the current transformer is an electromagnetic induction AC current transformer commonly used in power systems, capable of efficiently sensing AC current and exhibiting high measurement accuracy and stability. Furthermore, the intelligent switching device is a relay, semiconductor switch, or other switch type suitable for this method, ensuring high-precision control and rapid response. Furthermore, the switching device control system is capable of precisely controlling the switching device to switch at the zero-crossing point of the AC current in the primary winding of the current transformer, and the connection between the switching device and the current transformer has low resistance and low loss, ensuring measurement accuracy and avoiding measurement errors caused by inaccurate switching. Furthermore, when the switching device is closed, the current in the primary winding of the current transformer includes both DC and AC currents. Since the switching action occurs at the zero-crossing point of the AC current, the influence of the AC current is eliminated. According to Kirchhoff's current law, a portion of the DC current flows through the switch branch. Furthermore, a sudden change in the DC current value in the primary winding of the current transformer causes a sudden change in the induced current in its secondary winding, from which the magnitude of the DC current component in the primary winding can be inferred. Furthermore, the DC current has two directions relative to the switching device, corresponding to two types of measured sudden change signals: step-type sudden change and pulse-type sudden change. Furthermore, the switch closing time is controlled within one electrical signal cycle. That is, for 50Hz AC power, the switch closes for 0.02s and then reopens. Furthermore, since relay switching devices typically experience bounce during the closing process, requiring approximately 15μs to reach a steady-state closing condition, this bounce problem does not occur during the opening process, resulting in no delay in the opening stabilization. Therefore, the inferred DC current value of the signal at the moment the relay switching device opens is selected. Furthermore, the DC current value in the primary winding of the current transformer is directly proportional to the measured sudden change signal value. Furthermore, the DC current measurement is not affected by the magnitude of the AC current in the primary winding of the current transformer.

[0070] Example 1:

[0071] This embodiment discloses an innovative DC current measurement method based on a current transformer and an intelligent switch. If there is a positive DC current in the primary winding of the current transformer, the measurement and analysis process includes the following steps:

[0072] Step 1, the equivalent circuit diagram of the device is as follows Figure 1 As shown, the switch and the primary winding of the current transformer are in parallel, the resistance of the switch branch is very small and is in the same order of magnitude as the resistance of the current transformer, and the switch device can be controlled to perform switching action at the zero crossing point of the AC current.

[0073] Step 2: When the AC current passes through zero, the switch is controlled to close, and after a cycle of 0.02s, the switch is opened.

[0074] Step 3: According to Ampere's law, the DC current I dc The DC magnetic flux induced in the primary winding of the current transformer is φ dc =N1×µ0µ r ×S / l×I dc , where N1 represents the number of turns of the primary winding, µ0 is the magnetic permeability in vacuum, and µ r is the relative magnetic permeability of the current transformer core, S is the equivalent cross-sectional area of ​​the current transformer core, and l is the equivalent magnetic path length of the current transformer core.

[0075] Step 4: When the switch is closed, the DC current I dc Part of it will pass through the switch branch. According to the relationship between current and resistance, the DC magnetic flux in the current transformer core will suddenly decrease to (R switch / (R switch +R CT ))×φ dc , where R switch Represents the resistance of the switching device itself, R CT Indicates the resistance of the current transformer equivalent to the primary side, φ dc Indicates DC current I dc The DC flux induced in the primary winding of a current transformer.

[0076] Step 5: The sudden change of magnetic flux induces an electromotive force, which generates an induced current in the secondary winding of the current transformer. The induced current is proportional to the DC current in the primary winding of the current transformer.

[0077] Step 6, the forward DC current is measured through the current transformer and the switch device, and the result is Figure 2 The secondary winding current waveform shown is used to measure the step change in the secondary winding current at the moment the switch is turned off, and the DC flowing in the primary winding can be obtained.

[0078] Step 7: The relationship between the step change of the current in the secondary winding and the DC current value in the primary winding is as follows: Figure 3 The straight line in the first quadrant is shown.

[0079] Through the above steps, the forward DC current measurement in the AC power grid based on the current transformer and the intelligent switch can be realized.

[0080] Example 2:

[0081] This embodiment discloses an innovative DC current measurement method based on a current transformer and an intelligent switch. If there is a reverse DC current in the primary winding of the current transformer, the measurement and analysis process includes the following steps:

[0082] Step 1, the equivalent circuit diagram of the device is as follows Figure 1 As shown, the switch and the primary winding of the current transformer are in parallel, the resistance of the switch branch is very small and is in the same order of magnitude as the resistance of the current transformer, and the switch device can be controlled to perform switching action at the zero crossing point of the AC current.

[0083] Step 2: When the AC current crosses zero, the switch is controlled to close, and after a cycle of 0.02s, the switch is opened.

[0084] Step 3: According to Ampere's law, the DC current I dc A DC magnetic flux φ is generated in the primary winding of the current transformer. dc With DC current I dc , is proportional.

[0085] Step 4: When the switch is closed, the DC current I dc Part of it will pass through the switch branch, and the DC magnetic flux in the current transformer core will suddenly decrease to (R switch / (R switch +R CT ))×φ dc , where R switch Represents the resistance of the switching device itself, R CT Indicates the resistance of the current transformer equivalent to the primary side, φ dc Indicates DC current I dc The DC flux induced in the primary winding of a current transformer.

[0086] Step 5: The sudden change of magnetic flux induces an electromotive force, which generates an induced current in the secondary winding of the current transformer. The induced current is proportional to the DC current in the primary winding of the current transformer.

[0087] Step 6, the reverse DC current is measured through the current transformer and the switch device, and the result is Figure 4 The secondary winding current waveform shown is used to measure the pulse change in the secondary winding current at the moment the switch is turned off, and the DC flowing in the primary winding can be obtained.

[0088] Step 7: The relationship between the step change of the current in the secondary winding and the DC current value in the primary winding is as follows: Figure 3 As shown by the straight line in the third quadrant, the slope of this straight line is the same as the slope of the first quadrant, and it is the same direct proportional relationship.

[0089] Through the above steps, reverse DC current measurement in an AC power grid based on a current transformer and an intelligent switch can be achieved.

[0090] Example 3:

[0091] This embodiment discloses an innovative DC current measurement method based on a current transformer and an intelligent switch. If no DC current exists in the primary winding of the current transformer, the measurement and analysis process includes the following steps:

[0092] Step 1, the equivalent circuit diagram of the device is as follows Figure 1 As shown, the switch and the primary winding of the current transformer are in parallel, the resistance of the switch branch is very small and is in the same order of magnitude as the resistance of the current transformer, and the switch device can be controlled to perform switching action at the zero crossing point of the AC current.

[0093] Step 2: When the AC current passes through zero, the switch is controlled to close, and after a cycle of 0.02s, the switch is opened.

[0094] Step 3: According to Ampere's law, the AC magnetic flux generated by the AC current in the primary winding of the current transformer will suddenly decrease to the original value (R switch / (R switch +R CT )) times, where R switch Represents the resistance of the switching device itself, R CT It represents the resistance equivalent to the primary side of the current transformer.

[0095] Step 4: Since the switch is closed or opened when the AC crosses zero, no sudden change will occur in the secondary winding. The current waveform of the secondary winding during the switching action is as follows: Figure 5 shown.

[0096] In step 5, since there is no sudden change in the current in the secondary winding, that is, the sudden change is zero, the measured DC current is also zero, which is consistent with the actual state of the DC current in the power grid at this time.

[0097] Through the above steps, it can be shown that when there is no DC current in the AC power grid, the device based on the current transformer and the intelligent switch can also accurately reflect the state of zero DC current.

[0098] Example 4:

[0099] This embodiment discloses an innovative DC current measurement method based on a current transformer and an intelligent switch. If there is no AC current and only DC current in the primary winding of the current transformer, the measurement and analysis process includes the following steps:

[0100] Step 1, the equivalent circuit diagram of the device is as follows Figure 1As shown, the switch and the primary winding of the current transformer are in parallel, the resistance of the switch branch is very small and is in the same order of magnitude as the resistance of the current transformer, and the switch device can be controlled to perform switching action at the zero crossing point of the AC current.

[0101] Step 2: Since the AC current is continuously zero, the switch is randomly controlled to close at every moment when the AC current crosses the zero point, and after a cycle of 0.02s, the switch is opened.

[0102] Step 3: According to Ampere's law, the DC current I dc A DC magnetic flux φ is generated in the primary winding of the current transformer. dc With DC current I dc , is proportional.

[0103] Step 4: When the switch is closed, the DC current I dc Part of it will pass through the switch branch, and the DC magnetic flux in the current transformer core will suddenly decrease to (R switch / (R switch +R CT ))×φ dc , where R switch Represents the resistance of the switching device itself, R CT Indicates the resistance of the current transformer equivalent to the primary side, φ dc Indicates DC current I dc The DC flux induced in the primary winding of a current transformer.

[0104] Step 5: The sudden change of magnetic flux induces an electromotive force, which generates an induced current in the secondary winding of the current transformer. The induced current is proportional to the DC current in the primary winding of the current transformer.

[0105] Step 6, the DC current is measured through the current transformer and the switch device, and the Figure 6 The secondary winding current waveform shown is used to measure the pulse change of the secondary winding current at the moment the switch is turned off, and the DC value flowing through the primary winding can be obtained.

[0106] Step 7: The relationship between the step change of the current in the secondary winding and the DC current value in the primary winding remains the same. Figure 3 As shown in the straight line, the slope of this straight line is the same as when the AC current is not zero, and it is the same direct proportional relationship.

[0107] Through the above steps, DC current measurement based on the current transformer and the intelligent switch can be achieved when there is no AC current.

[0108] This invention effectively measures the DC component in an AC power grid. By connecting a switching device in parallel to the primary winding of a current transformer, the current path can be flexibly controlled without affecting the original circuit. This allows for subsequent precise measurement at specific moments (such as when the AC current crosses zero). The control system monitors the current signal in the secondary winding of the current transformer in real time and precisely controls the switching device to trigger when the AC current in the primary winding crosses zero. This precise control eliminates interference from the AC component during measurement and improves the accuracy of DC component measurement. When the switching device actuates, causing the current path to change, sudden current changes occur in the secondary winding of the current transformer. By analyzing the characteristics of these changes (such as step and pulse-type changes), the amplitude and direction of the DC current in the primary winding can be inferred. This method effectively addresses the problem of traditional current transformers being unable to directly measure DC. Using signal processing algorithms, such as a sudden current detection algorithm based on time-domain differentiation, to extract and analyze the current sudden current characteristics further improves data processing efficiency and accuracy. This is crucial for quickly and accurately acquiring DC current information.

[0109] There is a direct proportional relationship between the DC current value in the primary winding of a current transformer and the instantaneous change in the current amplitude in the secondary winding. This characteristic allows the DC current magnitude to be determined through simple linear calculations, simplifying the calculation process and improving the convenience and reliability of the measurement. This method is applicable not only to situations with AC components but also to situations with only DC current or no DC current. By adjusting the switching strategy, effective DC current measurement can be achieved under various complex operating conditions, enhancing the system's applicability and robustness. Relays or semiconductor switches are used as switching devices, ensuring high-precision control and fast response. These switching devices can complete state switching within microseconds, ensuring efficient and stable measurement.

[0110] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above-mentioned specific embodiments and application fields. The above-mentioned specific embodiments are merely illustrative and instructive, and are not restrictive. A person skilled in the art, guided by this specification and without departing from the scope of protection of the claims of the present invention, may also devise various forms, all of which fall within the scope of protection of the present invention.

Claims

1. A method for measuring direct current, characterized in that: The steps include: Connect the switchgear in parallel with the primary winding of the current transformer, A control system for the switch device is set up to monitor the current signal in the secondary winding of the current transformer in real time. The control system controls the switch device to operate when the primary winding AC current crosses the zero point and adjusts the control parameters. The switch device is triggered synchronously to operate, and the switch device is controlled to trigger the operation when the AC current of the primary winding of the current transformer passes through the zero point, so that the switch device is closed for one cycle and then opened. Detect the current mutation signal. When the switch device is disconnected, measure the current mutation characteristics in the secondary winding of the current transformer. Analyze the current mutation characteristics through the mutation detection algorithm signal processing algorithm based on time domain differentiation to obtain the instantaneous amplitude change result, and calculate the DC current component of the primary side. According to the positive and negative directions of the current mutation value, further determine the amplitude and direction of the DC current component in the primary winding, thereby realizing the measurement of DC current.

2. A DC current measurement method according to claim 1, characterized in that: Preferably, the current transformer includes an electromagnetic induction AC current transformer that senses AC current.

3. A DC current measurement method according to claim 1, characterized in that: The switching device includes a relay or a semiconductor switch.

4. A DC current measurement method according to claim 1, characterized in that: When the current in the primary winding of the current transformer contains a DC current component, the action of the switching device causes the current in the secondary winding of the current transformer to change suddenly.

5. A direct current measurement method according to claim 1, characterized in that: The current mutation characteristics include step mutation and pulse mutation.

6. A direct current measurement method according to claim 1, characterized in that: The current mutation characteristics are extracted and analyzed through peak detection.

7. A direct current measurement method according to claim 1, characterized in that: The step change of the current in the secondary winding is directly proportional to the DC current value in the primary winding.

8. A system for implementing the method according to any one of claims 1 to 7, characterized in that: It includes: a current transformer comprising a primary winding, a switching device connected in parallel with the primary winding, A control system is connected to and controls the switch device to monitor the current signal in the secondary winding of the current transformer in real time. The control system controls the switch device to operate when the primary winding AC current crosses zero and adjusts the control parameters. The trigger module is used to synchronously trigger the action of the switch device, controlling the switch device to trigger the action when the AC current of the primary winding of the current transformer passes through the zero point, so that the switch device closes for one cycle and then opens. The detection module is used to detect the current mutation signal. When the switch device is disconnected, the current mutation characteristics in the secondary winding of the current transformer are measured, and the current mutation characteristics are analyzed by the signal processing algorithm to obtain the analysis results. The measuring module is used to calculate the DC current component and determine the amplitude and direction of the DC current component in the primary winding according to the analysis result, thereby realizing the measurement of the DC current.

9. A computer storage medium, characterized in that The storage medium includes computer instructions, which, when executed on a computer, enable the computer to perform the method according to any one of claims 1 to 7.

10. An electronic device, characterized in that: The electronic device comprises: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the method according to any one of claims 1 to 7 is implemented.

Images