Current transformer and control method and control device thereof

Abstract

The invention provides a current transformer and a control method and device thereof, the current transformer comprises an iron core, a primary winding, a secondary winding, a detection winding and a detection module, the primary winding, the secondary winding and the detection winding are wound on the iron core, and the detection module is connected with the detection winding and the secondary winding; the primary winding is used for receiving current to be measured and generating magnetic flux in the iron core; the secondary winding is used for generating an output current based on the magnetic flux; the detection winding is used for measuring the excitation voltage of the current transformer; and the detection module is used for generating a control signal based on the excitation voltage, and the control signal is used for adjusting the output current, so that the current transformer is in a zero magnetic flux state. According to the current transformer, zero magnetic flux is achieved, the measurement precision is higher, the structure is simple, and implementation is easy.

Description

Technical Field

[0001] The present disclosure relates to the field of electronic technology, and in particular to a current transformer and a control method and a control device thereof. Background Art

[0002] The current transformer is an instrument that converts a large current on the primary side into a small current on the secondary side for measurement based on the principle of electromagnetic induction. It is mainly composed of an iron core, a primary winding, and a secondary winding. During the measurement process, the measured current excites the magnetic potential through the primary winding, which induces a magnetic flux in the iron core, and then induces an electromotive force in the secondary winding, driving the secondary current to flow. According to the magnetic potential balance theory, the primary magnetic potential is mainly used to balance the secondary magnetic potential, while the remaining small part is used for core excitation to form an excitation magnetic potential. In order to improve the measurement accuracy, the influence of the excitation magnetic potential needs to be reduced. Therefore, how to simply and effectively reduce the influence of the excitation magnetic flux on the measurement has become an urgent problem to be solved. Summary of the invention

[0003] The present disclosure provides a current transformer and a control method and a control device thereof, so as to at least solve the above technical problems existing in the prior art.

[0004] According to a first aspect of the present disclosure, a current transformer is provided, the current transformer comprising: an iron core, a primary winding, a secondary winding, a detection winding and a detection module, the primary winding, the secondary winding and the detection winding are wound on the iron core, and the detection module is connected to the detection winding and the secondary winding;

[0005] The primary winding is used to receive the current to be measured and generate magnetic flux in the iron core;

[0006] The secondary winding is used to generate an output current based on the magnetic flux;

[0007] The detection winding is used to measure the excitation voltage of the current transformer;

[0008] The detection module is used to generate a control signal based on the excitation voltage, and the control signal is used to adjust the output current so that the current transformer is in a zero flux state.

[0009] In one possible implementation manner, the current transformer further includes a measuring resistor, which is connected to the secondary winding and is used to measure the output current.

[0010] In one possible implementation manner, the detection winding is in a high-resistance state, so that the current to be measured does not flow through the detection winding.

[0011] In one possible implementation, the detection module is a proportional-integral controller.

[0012] In one possible implementation, the proportional-integral controller is used to:

[0013] Comparing the excitation voltage with the predicted reference voltage to obtain an error value;

[0014] Based on the error value, the control signal is generated.

[0015] According to a second aspect of the present disclosure, a method for controlling a current transformer is provided, the method comprising:

[0016] receiving a current to be measured;

[0017] Obtaining an output current based on the magnetic flux generated by the current to be measured;

[0018] Obtaining an excitation voltage of the current transformer;

[0019] A control signal is generated based on the excitation voltage, wherein the control signal is used to adjust the output current so that the current transformer is in a zero flux state.

[0020] In one possible implementation manner, generating a control signal based on the excitation voltage includes:

[0021] Comparing the excitation voltage with the predicted reference voltage to obtain an error value;

[0022] Based on the error value, the control signal is generated.

[0023] In one possible implementation manner, obtaining the excitation voltage of the current transformer includes:

[0024] The voltage of the detection winding is obtained, and the voltage of the detection winding is used as the excitation voltage.

[0025] According to a third aspect of the present disclosure, a control device for a current transformer is provided, comprising:

[0026] A current receiving module, used for receiving the current to be measured;

[0027] A magnetic flux conversion module, used for obtaining an output current based on the magnetic flux generated by the current to be measured;

[0028] An excitation measurement module, used for obtaining the excitation voltage of the current transformer;

[0029] The regulating module is used to generate a control signal based on the excitation voltage, and the control signal is used to adjust the output current so that the current transformer is in a zero flux state.

[0030] According to a fourth aspect of the present disclosure, a non-transitory computer-readable storage medium storing computer instructions is provided, wherein the computer instructions are used to cause the computer to execute the method described in the present disclosure.

[0031] The disclosed current transformer and its control method and control device only need to add a coil (detection winding) and a detection module on the basis of an ordinary transformer, and then obtain the excitation voltage by detecting the voltage of the winding, and then adjust the output current according to the excitation voltage to obtain a current transformer with zero flux function. This solution not only improves the accuracy and stability of current measurement, but also enhances the adaptability and scalability of the equipment, providing strong support for the safe operation and efficient management of the power system.

[0032] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present disclosure are shown in an exemplary and non-limiting manner, in which:

[0034] In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0035] Figure 1 A schematic diagram of the structure of a current transformer in the prior art is shown;

[0036] Figure 2 A schematic diagram of an equivalent circuit of a current transformer according to an embodiment of the present disclosure is shown;

[0037] Figure 3 A schematic diagram of an implementation flow of a method for controlling a current transformer according to an embodiment of the present disclosure is shown;

[0038] Figure 4 A schematic diagram of the structure of a control device for a current transformer according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0039] In order to make the purpose, features, and advantages of the present disclosure more obvious and easy to understand, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0040] The current transformer is an important device for current measurement in the power system. It is mainly composed of an iron core and two windings (primary winding N1 and secondary winding N2). When the measured current I1 passes through the primary winding N1, according to Ampere's loop law, a primary magnetic potential, namely N1I1, is generated around the winding. The primary magnetic potential excites a magnetic flux in the iron core. Magnetic Flux When passing through the secondary winding N2, according to Faraday's law of electromagnetic induction, an induced potential E2 is generated in the secondary winding. This induced potential drives the current I2 in the secondary winding to flow, thereby realizing the measurement of the primary side current on the secondary side.

[0041] As the secondary current I2 flows, the secondary winding N2 itself will also generate a back electromotive force N2I2. According to the magnetic potential balance principle, the magnetic potential balance equation of the current transformer can be expressed as: I1N1+I2N2=I0N1. It can be seen that the primary magnetic potential I1N1 is mainly composed of two parts: one is the part used to balance the secondary magnetic potential I2N2, which is approximately equal to the primary magnetic potential in magnitude and opposite in direction. The other is the excitation magnetic potential I0N1 used for core excitation. The excitation magnetic potential will cause the secondary current I2 to deviate from the strictly proportional relationship with the primary current I1, thus causing measurement errors.

[0042] refer to Figure 1 As shown in the figure, in order to solve the measurement error caused by the excitation magnetic potential, the commonly used solution is to use a zero flux transformer with a bipolar structure (T1 as the auxiliary iron core and T2 as the main iron core). The main iron core T2 of the zero flux transformer is provided with a detection winding (used to sense the change of magnetic flux in the main iron core and generate an induced voltage) and a measurement winding (used to output a secondary current proportional to the measured current). The auxiliary iron core T1 is provided with a compensation winding. The function of the auxiliary iron core T1 and the compensation winding is to generate a magnetic flux opposite to the excitation current in the main iron core T2 to offset the influence of the excitation current.

[0043] Specifically, when the measured current passes through the main iron core, a magnetic flux is generated in the main iron core. If there is an excitation current in the main iron core, an induced voltage related to the excitation current is induced on the detection winding. The signal conditioning circuit receives the induced voltage of the detection winding and processes it to obtain a voltage signal proportional to the excitation current in the main iron core. The transconductance amplifier circuit converts the voltage signal output by the signal conditioning circuit into a current signal and drives the compensation winding. In order to generate a magnetic flux opposite to the excitation current in the main iron core, the net magnetic flux in the main iron core approaches zero, thereby achieving a zero magnetic flux state.

[0044] However, the above-mentioned zero flux transformer has high requirements in terms of consistency of magnetic properties of T1 and T2, structural integrity, winding distribution and coupling, compensation circuit integration, material selection and processing accuracy. It is difficult to manufacture and cannot be achieved through later modification of ordinary current transformers.

[0045] In response to the above problems, according to the first aspect of the present disclosure, a current transformer is provided, which includes: an iron core, a primary winding, a secondary winding, a detection winding and a detection module, the primary winding, the secondary winding and the detection winding are wound on the iron core, and the detection module is connected to the detection winding and the secondary winding; the primary winding is used to receive the current to be measured and generate a magnetic flux in the iron core; the secondary winding is used to generate an output current based on the magnetic flux; the detection winding is used to measure the excitation voltage of the current transformer; the detection module is used to generate a control signal based on the excitation voltage, and the control signal is used to adjust the output current so that the current transformer is in a zero flux state.

[0046] The core is the core component of the current transformer and is made of a material with high magnetic permeability (such as ferrite or silicon steel sheet). The core provides a closed magnetic circuit, so that the current flowing through the primary winding can generate magnetic flux in the core. The primary winding is the part of the current transformer that is directly connected to the circuit to be measured and is used to receive the current to be measured. When the current to be measured passes through the primary winding, a corresponding magnetic flux is generated in the core. The secondary winding is set on the core and is coupled with the primary winding. When the magnetic flux in the core changes, an electromotive force is induced in the secondary winding, thereby generating an output current. The detection winding is set on the core and is used to measure the excitation voltage. The excitation voltage is the voltage required to maintain the magnetic flux in the core.

[0047] Figure 2 The equivalent circuit diagram of a current transformer according to an embodiment of the present disclosure is shown, wherein Z1, Z2 and Z m They are the equivalent impedance and excitation impedance of the primary winding and secondary winding, respectively, Z2 ′ It is used to measure the excitation voltage of the measuring winding. I1 is the current to be measured, I L is the output current. Specifically, the detection module receives the excitation voltage from the detection winding, and then generates a control signal based on the excitation voltage. The control signal is used to adjust the output current of the secondary winding to offset the magnetic flux generated by the primary winding in the iron core, so that the excitation voltage will be zero. When the excitation voltage is 0, Z m No current will flow, achieving zero flux. The detection module continuously monitors the excitation voltage and adjusts the output current of the secondary winding as needed, forming a closed loop state.

[0048] The current transformer of this embodiment is a current transformer with zero flux function, which can be obtained by adding a coil (detection winding) to the ordinary current transformer. This solution not only improves the accuracy and stability of current measurement, but also enhances the adaptability and scalability of the equipment, providing strong support for the safe operation and efficient management of the power system.

[0049] According to another embodiment of the present disclosure, the current transformer further includes a measuring resistor, which is connected to the secondary winding and is used to measure the output current.

[0050] like Figure 2 As shown, R s It is a measuring resistor used to measure the output current generated by the secondary winding. The output current is converted into a voltage signal by measuring the resistor, so that the current value can be easily read and recorded using a voltmeter or other measuring equipment. Specifically, when current flows through the secondary winding, this current may pass through the measuring resistor in series with it. According to Ohm's law, the voltage drop across the resistor is proportional to the current flowing through it. Therefore, by measuring this voltage drop, the current in the secondary winding can be indirectly obtained.

[0051] According to another embodiment of the present disclosure, the detection winding is in a high-resistance state so that the current to be measured does not flow through the detection winding.

[0052] In order to ensure that the current to be measured does not flow through the detection winding, the detection winding is designed to be in a high impedance state. This ensures that in the no-load (open circuit) state, the voltage on the detection winding can be equivalent to the voltage on the excitation impedance, that is, the excitation voltage.

[0053] According to another embodiment of the present disclosure, the detection module is a proportional-integral controller, which is used to: compare the excitation voltage with the predicted reference voltage to obtain an error value; and generate the control signal based on the error value.

[0054] The detection module uses a proportional-integral controller, which compares the detected excitation voltage with the preset predicted reference voltage and calculates the error value between the two. Then, based on this error value, the proportional-integral controller uses its internal algorithm to generate a corresponding control signal to adjust the output current of the secondary winding, thereby achieving precise control of the current transformer state and ensuring that the current transformer can maintain a zero flux state.

[0055] According to another aspect of the present disclosure, a method for controlling a current transformer is provided, such as Figure 3 As shown, the method comprises the following steps:

[0056] Step 101, receiving a current to be measured;

[0057] Step 102, obtaining an output current based on the magnetic flux generated by the current to be measured;

[0058] Step 103, obtaining the excitation voltage of the current transformer;

[0059] Step 104: Generate a control signal based on the excitation voltage, wherein the control signal is used to adjust the output current so that the current transformer is in a zero flux state.

[0060] According to another embodiment of the present disclosure, obtaining the excitation voltage of the current transformer includes: acquiring a voltage of a detection winding, and using the voltage of the detection winding as the excitation voltage.

[0061] According to another embodiment of the present disclosure, generating a control signal based on the excitation voltage includes: comparing the excitation voltage with a predicted reference voltage to obtain an error value; and generating the control signal based on the error value.

[0062] According to another aspect of the present disclosure, a control device for a current transformer is provided, such as Figure 4 As shown, the device includes the following modules:

[0063] A current receiving module 301 is used to receive a current to be measured;

[0064] A magnetic flux conversion module 302, configured to obtain an output current based on the magnetic flux generated by the current to be measured;

[0065] An excitation measurement module 303, used to obtain the excitation voltage of the current transformer;

[0066] The regulating module 304 is used to generate a control signal based on the excitation voltage, wherein the control signal is used to adjust the output current so that the current transformer is in a zero flux state.

[0067] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved, and this document does not limit this.

[0068] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0069] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A current transformer, characterized in that: The current transformer comprises: an iron core, a primary winding, a secondary winding, a detection winding and a detection module, wherein the primary winding, the secondary winding and the detection winding are wound on the iron core, and the detection module is connected to the detection winding and the secondary winding; The primary winding is used to receive the current to be measured and generate magnetic flux in the iron core; The secondary winding is used to generate an output current based on the magnetic flux; The detection winding is used to measure the excitation voltage of the current transformer; The detection module is used to generate a control signal based on the excitation voltage, and the control signal is used to adjust the output current so that the current transformer is in a zero flux state.

2. The current transformer according to claim 1, characterized in that: The current transformer further comprises a measuring resistor, which is connected to the secondary winding and is used to measure the output current.

3. The current transformer according to claim 1, characterized in that: The detection winding is in a high-impedance state so that the current to be measured does not flow through the detection winding.

4. The current transformer according to claim 1, characterized in that: The detection module is a proportional-integral controller.

5. The current transformer according to claim 4, wherein the proportional-integral controller is used for: Comparing the excitation voltage with the predicted reference voltage to obtain an error value; Based on the error value, the control signal is generated.

6. A method for controlling a current transformer, characterized in that: The method comprises: receiving a current to be measured; Obtaining an output current based on the magnetic flux generated by the current to be measured; Obtaining an excitation voltage of the current transformer; A control signal is generated based on the excitation voltage, wherein the control signal is used to adjust the output current so that the current transformer is in a zero flux state.

7. The control method according to claim 6, characterized in that: The obtaining of the excitation voltage of the current transformer comprises: The voltage of the detection winding is obtained, and the voltage of the detection winding is used as the excitation voltage.

8. The control method according to claim 6, characterized in that: The step of generating a control signal based on the excitation voltage comprises: Comparing the excitation voltage with the predicted reference voltage to obtain an error value; Based on the error value, the control signal is generated.

9. A control device for a current transformer, characterized in that: The device comprises: A current receiving module, used for receiving the current to be measured; A magnetic flux conversion module, used for obtaining an output current based on the magnetic flux generated by the current to be measured; An excitation measurement module, used for obtaining the excitation voltage of the current transformer; The regulating module is used to generate a control signal based on the excitation voltage, and the control signal is used to adjust the output current so that the current transformer is in a zero flux state.

10. A non-transitory computer-readable storage medium storing computer instructions, characterized in that: The computer instructions are used to make a computer execute the method according to any one of claims 6-8.

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