Current measurement circuit for three-phase zero-crossing switching of power distribution system

Abstract

The utility model discloses a current measurement circuit for three-phase zero-crossing switching of a power distribution system, and the circuit is characterized in that in each current measurement sub-circuit, a power supply of a corresponding phase is connected to one side of a primary winding of a current transformer through a first resistor, a neutral line power supply is connected to the other side of the primary winding through a second resistor, and a neutral line power supply is connected to the other side of the secondary winding through a third resistor; the reference voltage source is connected to the non-inverting input end of the operational amplifier through the third resistor and the fourth resistor in sequence, the inverting input end of the operational amplifier is in butt joint with the output end, and the output end of the operational amplifier is connected to a digital conversion input channel corresponding to the microcontroller. Therefore, the current transformer can accurately convert the large current in the AC power supply into the small current according to a certain proportion, so that the current flowing through the capacitor can be accurately measured in the reactive compensation device of the power distribution system, and the amplified signal is smoothly output to the microcontroller, so that the amplified signal is directly and efficiently butted with the microcontroller and intelligently processed; therefore, the requirement of a power distribution system for three-phase zero-crossing switching is met.

Description

Technical Field

[0001] This application relates to the field of circuit technology, and more specifically, to a current measurement circuit for three-phase zero-crossing switching in a power distribution system. Background Technology

[0002] In the operation and management of power systems, zero-crossing switching technology plays a crucial role in reactive power compensation and precise control of power equipment. Traditional zero-crossing switching control faces numerous challenges during implementation, with accurate measurement and effective processing of AC current being a critical aspect. Early power measurement technologies lacked sufficient accuracy and reliability for AC current measurement, failing to meet the high requirements of current monitoring in modern power systems for zero-crossing switching control. On one hand, traditional current measurement methods cannot effectively convert and accurately measure large currents, easily leading to signal distortion and significant errors. On the other hand, the lack of effective anti-interference measures during signal transmission and processing allows the complex electromagnetic environment of the power system to introduce substantial noise and interference signals, resulting in unstable measurement results and consequently affecting the accuracy and reliability of zero-crossing switching.

[0003] Therefore, how to accurately measure the current signal so as to directly and efficiently interface with the microcontroller and perform intelligent processing to meet the needs of the power distribution system for three-phase zero-crossing switching is an issue that needs attention. Utility Model Content

[0004] In view of the above problems, this application provides a current measurement circuit for three-phase zero-crossing switching in a power distribution system, so as to accurately measure the current signal, directly and efficiently interface with a microcontroller for intelligent processing, and meet the needs of power distribution systems for three-phase zero-crossing switching.

[0005] To achieve the above objectives, the following specific solutions are proposed:

[0006] A current measurement circuit for three-phase zero-crossing switching in a power distribution system includes four current measurement sub-circuits, namely, an A-phase current measurement sub-circuit, a B-phase current measurement sub-circuit, a C-phase current measurement sub-circuit, and a user-side current measurement sub-circuit.

[0007] Each current measurement subcircuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a current transformer, and an operational amplifier;

[0008] For each current measurement sub-circuit, the power supply corresponding to the current measurement sub-circuit is connected to one side of the primary winding of the current transformer through the first resistor, and the neutral power supply is connected to the other side of the primary winding through the second resistor;

[0009] In the secondary winding of the current transformer in each current measurement sub-circuit, the first reference voltage source is connected to the non-inverting input terminal of the operational amplifier through the third resistor and the fourth resistor in sequence. The inverting input terminal of the operational amplifier is connected to the output terminal of the operational amplifier. The output terminal of the operational amplifier is connected to the corresponding digital conversion input channel of the microcontroller through the fifth resistor.

[0010] Optionally, the A-phase current measuring sub-circuit further includes a first capacitor and a second capacitor;

[0011] In the phase A current measurement sub-circuit, the first capacitor and the second capacitor form a parallel circuit. One end of the parallel circuit is connected to the second reference voltage source, and the other end of the parallel circuit is grounded.

[0012] By employing the above technical solution, this application connects the power supply of the corresponding phase to one side of the primary winding of the current transformer through a first resistor in each current measurement sub-circuit, and the neutral power supply to the other side of the primary winding through a second resistor. In the secondary winding, the first reference voltage source is connected to the non-inverting input of the operational amplifier through a third and a fourth resistor, the inverting input of the operational amplifier is connected to the output, and the output of the operational amplifier is connected to the corresponding digital conversion input channel of the microcontroller through a fifth resistor. Thus, the current transformer can accurately convert a large current in the AC power supply into a small current according to a certain ratio, facilitating accurate measurement of the current flowing through the capacitor in the reactive power compensation device of the power distribution system. The amplified signal is smoothly output to the microcontroller, enabling efficient direct interface and intelligent processing to meet the requirements of the power distribution system for three-phase zero-crossing switching. Attached Figure Description

[0013] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0014] Figure 1 This is a schematic diagram of a current measurement circuit for three-phase zero-crossing switching in a power distribution system, provided as an embodiment of this application. Detailed Implementation

[0015] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0016] Figure 1 This application provides an embodiment of a current measurement circuit for three-phase zero-crossing switching in a power distribution system, such as... Figure 1 As shown, the current measurement circuit may include four current measurement sub-circuits.

[0017] Specifically, the four current measurement sub-circuits are the A-phase current measurement sub-circuit, the B-phase current measurement sub-circuit, the C-phase current measurement sub-circuit, and the user-side current measurement sub-circuit.

[0018] like Figure 1 As shown, Figure 1 The four current measurement sub-circuits from top to bottom are, in order, the A-phase current measurement sub-circuit, the B-phase current measurement sub-circuit, the C-phase current measurement sub-circuit, and the user-side current measurement sub-circuit.

[0019] Each current measurement sub-circuit may include a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a current transformer, and an operational amplifier.

[0020] Furthermore, for each current measurement sub-circuit, the power supply corresponding to the current measurement sub-circuit is connected to one side of the primary winding of the current transformer through the first resistor, and the neutral power supply is connected to the other side of the primary winding through the second resistor.

[0021] Furthermore, in the secondary winding of the current transformer in each current measurement sub-circuit, the first reference voltage source is connected sequentially to the non-inverting input of the operational amplifier through the third and fourth resistors, and the inverting input of the operational amplifier is connected to its output. The output of the operational amplifier is connected to the corresponding digital conversion input channel of the microcontroller through the fifth resistor.

[0022] The first and second resistors are both 100kΩ, serving as current limiters. The third resistor has a resistance of 0. The fourth resistor has a resistance of 1kΩ. The fifth resistor has a resistance of 10kΩ. The current transformer is model ZMPT107-1, used to convert large currents into smaller currents for easier measurement. The operational amplifier is model LM324DT, which forms an amplifier circuit to amplify the small voltage signal output from the current transformer.

[0023] Specifically, such as Figure 1As shown, for the A-phase current measurement sub-circuit, the A-phase power supply UA is connected to one side of the primary winding of the current transformer PT1 via the first resistor R16, and the neutral power supply UN is connected to the other side of the primary winding of the current transformer PT1 via the second resistor R17. In the magnetic pole winding of the current transformer PT1, the first reference voltage source VREF is connected to the non-inverting input terminal "+" of the operational amplifier U4.1 via the third resistor R18 and the fourth resistor RN1. The inverting input terminal "-" of the operational amplifier U4.1 is connected to the output terminal of the operational amplifier U4.1. The output terminal of the operational amplifier U4.1 is connected to the corresponding digital conversion input channel MCU_AD_UA of the microcontroller via the fifth resistor R19.

[0024] For the B-phase current measurement sub-circuit, the B-phase power supply UB is connected to one side of the primary winding of the current transformer PT2 via the first resistor R20, and the neutral power supply UN is connected to the other side of the primary winding of the current transformer PT2 via the second resistor R21. In the magnetic pole winding of the current transformer PT2, the first reference voltage source VREF is connected to the non-inverting input terminal "+" of the operational amplifier U4.2 via the third resistor R22 and the fourth resistor RN2. The inverting input terminal "-" of the operational amplifier U4.2 is connected to the output terminal of the operational amplifier U4.2. The output terminal of the operational amplifier U4.2 is connected to the corresponding digital conversion input channel MCU_AD_UB of the microcontroller via the fifth resistor R23.

[0025] For the C-phase current measurement sub-circuit, the C-phase power supply UC is connected to one side of the primary winding of the current transformer PT3 via the first resistor R24, and the neutral power supply UN is connected to the other side of the primary winding of the current transformer PT3 via the second resistor R25. In the magnetic pole winding of the current transformer PT3, the first reference voltage source VREF is connected to the non-inverting input terminal "+" of the operational amplifier U4.3 via the third resistor R26 and the fourth resistor RN3. The inverting input terminal "-" of the operational amplifier U4.3 is connected to the output terminal of the operational amplifier U4.3. The output terminal of the operational amplifier U4.3 is connected to the corresponding digital conversion input channel MCU_AD_UC of the microcontroller via the fifth resistor R27.

[0026] For the user-side current measurement sub-circuit, the power supply UL is connected to one side of the primary winding of the current transformer PT4 via the first resistor R28, and the neutral power supply UN is connected to the other side of the primary winding of the current transformer PT4 via the second resistor R29. In the magnetic pole winding of the current transformer PT4, the first reference voltage source VREF is connected to the non-inverting input terminal "+" of the operational amplifier U4.4 via the third resistor R30 and the fourth resistor RN4. The inverting input terminal "-" of the operational amplifier U4.4 is connected to the output terminal of the operational amplifier U4.4. The output terminal of the operational amplifier U4.4 is connected to the corresponding digital conversion input channel MCU_AD_UL of the microcontroller via the fifth resistor R31.

[0027] Understandably, current transformers can accurately convert large currents in AC power sources into smaller currents according to a certain ratio, facilitating subsequent measurement and processing. For example, in reactive power compensation devices in power systems, accurately measuring the current flowing through capacitors allows for precise control of capacitor switching based on current magnitude and phase, optimizing reactive power compensation, reducing energy loss, and improving the power factor of the power system. Operational amplifiers amplify the small voltage signal output from the current transformer, increasing its amplitude and making it easier for the microcontroller to recognize and process. The amplified voltage signal can be smoothly output to the microcontroller's digital input channel, directly connecting to the microcontroller's analog input port, achieving efficient integration between the current measurement circuit and the microcontroller. The microcontroller can perform real-time analysis and processing of the measured signal, accurately determining the zero-crossing moment based on current changes, and performing switching operations at the most appropriate time, improving the response speed and control accuracy of zero-crossing switching, ensuring the stable operation of the power system and the safe and reliable operation of equipment.

[0028] Furthermore, the A-phase current measuring sub-circuit can also include a first capacitor and a second capacitor, such as... Figure 1 As shown, the first capacitor and the second capacitor are C9 and C10, respectively.

[0029] Specifically, in the A-phase current measurement sub-circuit, the first capacitor C9 and the second capacitor C10 form a parallel circuit. One end of the parallel circuit is connected to the second reference voltage source, and the other end of the parallel circuit is grounded.

[0030] The second reference voltage source is a 5V voltage source.

[0031] Understandably, the filter circuit composed of capacitors C9 and C10 effectively reduces the interference of power supply noise on the measurement signal, ensuring the accuracy and stability of the signal transmitted to the microcontroller. In industrial power control scenarios, even in environments with electromagnetic interference from numerous electrical devices, it can still accurately acquire AC current signals, providing a reliable basis for zero-crossing switching control.

[0032] The power distribution system provided in this embodiment uses a current measurement circuit for three-phase zero-crossing switching. In each current measurement sub-circuit, the power supply of the corresponding phase is connected to one side of the primary winding of the current transformer through a first resistor, and the neutral power supply is connected to the other side of the primary winding through a second resistor. In the secondary winding, a first reference voltage source is connected to the non-inverting input of an operational amplifier through a third and a fourth resistor, respectively. The inverting input of the operational amplifier is connected to its output, and the output of the operational amplifier is connected to the corresponding digital conversion input channel of the microcontroller through a fifth resistor. Therefore, the current transformer can accurately convert a large current in the AC power supply into a small current according to a certain ratio, facilitating accurate measurement of the current flowing through the capacitor in the reactive power compensation device of the power distribution system. The amplified signal is smoothly output to the microcontroller, enabling efficient direct interface and intelligent processing to meet the requirements of the power distribution system for three-phase zero-crossing switching.

[0033] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0034] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0035] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A current measurement circuit for three-phase zero-crossing switching in a power distribution system, characterized in that, It includes four current measurement sub-circuits, namely, the A-phase current measurement sub-circuit, the B-phase current measurement sub-circuit, the C-phase current measurement sub-circuit, and the user-side current measurement sub-circuit; Each current measurement subcircuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a current transformer, and an operational amplifier; For each current measurement sub-circuit, the power supply corresponding to the current measurement sub-circuit is connected to one side of the primary winding of the current transformer through the first resistor, and the neutral power supply is connected to the other side of the primary winding through the second resistor; In the secondary winding of the current transformer in each current measurement sub-circuit, the first reference voltage source is connected to the non-inverting input terminal of the operational amplifier through the third resistor and the fourth resistor in sequence. The inverting input terminal of the operational amplifier is connected to the output terminal of the operational amplifier. The output terminal of the operational amplifier is connected to the corresponding digital conversion input channel of the microcontroller through the fifth resistor.

2. The current measuring circuit according to claim 1, characterized in that, The phase A current measurement sub-circuit also includes a first capacitor and a second capacitor; In the phase A current measurement sub-circuit, the first capacitor and the second capacitor form a parallel circuit. One end of the parallel circuit is connected to the second reference voltage source, and the other end of the parallel circuit is grounded.

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