Three-phase three-wire current acquisition circuit adaptive to distribution network terminal and control method

Abstract

According to the three-phase three-wire current acquisition circuit adaptive to the distribution network terminal and the control method, the three-phase three-wire current acquisition circuit comprises a current acquisition circuit, a signal amplification circuit, a metering and processing circuit, an operational amplifier and a multi-stage anti-interference design, and conversion from large current to small current is realized through elements such as a current transformer, a magnetic bead, a transient voltage suppression diode and a sampling resistor; current signals are converted into voltage signals, and electromagnetic interference and high-frequency noise are effectively suppressed; the precision and the amplitude of the signal are improved; data storage, processing and communication are achieved through the electric energy metering chip, the MCU, the resistor, the capacitor and other elements, the precision and reliability of current collection are remarkably improved through multi-level signal processing and anti-interference design, the reference requirements in the complex electromagnetic environment can be effectively met, and high-quality current data support is provided for power distribution network terminal equipment; the current collector is widely applied to a distribution network terminal unit and a power management system, and can complete a current accurate collection task in a complex electromagnetic environment.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network automation. Specifically, it relates to a three-phase three-wire current acquisition circuit and control method adapted to distribution network terminals. Background Art

[0002] Driven by technologies such as 5G communication, Internet of Things, and edge computing, the construction process of intelligent and low-carbon distribution networks has been gradually accelerating, making the accuracy and reliability of data acquisition, transmission, and processing for distribution network terminal devices an important topic and a key breakthrough technology in current research in this field.

[0003] Current acquisition, as one of the most widely used technologies in intelligent distribution networks, plays an important role in the monitoring, analysis, and optimal dispatching of distribution network systems. However, traditional current acquisition methods mostly use single analog signal acquisition circuits, which are difficult to meet the requirements of high-precision data acquisition in complex electromagnetic environments. Moreover, with the accelerating intelligent process of intelligent distribution network technology, traditional current acquisition technology also faces problems such as severe signal noise interference, insufficient response speed, weak anti-interference ability, and low measurement accuracy, making it difficult to provide accurate and reliable data support and restricting the intelligent development of distribution network systems.

[0004] In response to the above problems, many invention researches have begun to attempt to use high-precision metering chips and innovative circuit designs to break through the limitations of traditional current acquisition modes and propose current acquisition schemes suitable for current distribution network requirements. For example, the patent with publication number CN209707588U proposes a three-phase voltage and current acquisition device for PMU, which improves the accuracy and speed of current signal acquisition by designing 3 current acquisition circuits and signal conditioning circuits to collect and condition the three-phase current signals of transmission lines. The patent with publication number CN103675431A proposes a current acquisition device on a power transmission line, and this invention solves the technical problem that the original current acquisition requires an external power supply. The patent with publication number CN111398670A proposes a three-phase three-wire voltage and current signal acquisition circuit, which can be applied to multi-loop combination scenarios such as single-phase and three-phase, realizes high and low voltage isolation, and has good anti-interference ability. The patent with publication number CN114527318A proposes a high-voltage AC voltage acquisition circuit. By designing to connect the current acquisition circuit in parallel between the input lines of the measured high voltage, the high voltage signal is then converted into a current signal, avoiding the influence of external high voltage signals on the measurement and effectively improving the measurement accuracy. The patent with publication number 110187164A proposes a circuit for accurately acquiring the zero-crossing point of alternating current, effectively reducing the error between the zero-crossing point signal and the actual zero-crossing point of the current waveform and improving the measurement accuracy and precision.

[0005] Although the above-mentioned invention research has enhanced the current data acquisition ability to a certain extent, improved the anti-interference ability and response speed of the acquisition system, ensured good acquisition accuracy, and can meet the current current acquisition requirements, however, with the increasing complexity of the distribution network system and the large-scale access of distributed energy to the power grid, the current acquisition system is facing more severe challenges. Moreover, under the influence of high-frequency noise and instantaneous voltage fluctuations of the current signal, it is still difficult to ensure the acquisition accuracy and data stability. In addition, the intelligent distribution network has an increasing demand for data transmission speed and real-time output ability, resulting in higher requirements for the design of the current acquisition circuit. Therefore, designing a current acquisition circuit with strong anti-interference ability, high acquisition speed, fast response speed, high precision, etc. has become the main direction of current research and invention.

[0006] Based on this demand, the present invention designs a three-phase three-wire current acquisition circuit adapted to the distribution network terminal, which integrates a high-precision metering chip, a signal amplification circuit and a processing unit. Through multi-level signal processing and anti-interference design, it significantly improves the accuracy and reliability of current acquisition, can effectively meet the application requirements in a complex electromagnetic environment, and provides high-quality current data support for the distribution network terminal equipment. Summary of the Invention

[0007] In view of the above deficiencies in the prior art, the present invention provides a three-phase three-wire current acquisition circuit adapted to the distribution network terminal with strong anti-interference ability, high acquisition speed, fast response speed and high precision.

[0008] The technical solution adopted by the present invention is as follows: A three-phase three-wire current acquisition circuit adapted to the distribution network terminal, Two input ends of the first current transformer T1 are respectively connected to the A-phase end and the ground end of the three-phase power; The output end of the first current transformer T1 is respectively connected to one end of the first magnetic bead FB1 and the second magnetic bead FB2; The other ends of the first magnetic bead FB1 and the second magnetic bead FB2 are connected through the first transient voltage suppression diode TVS1; The other end of the second magnetic bead FB2 is grounded; The other end of the first magnetic bead FB1 is grounded through the first sampling resistor R1; The other end of the first magnetic bead FB1 is connected to the +INA pin of the third operational amplifier U3; The -INA pin of the third operational amplifier U3 is connected to the OUTA pin of the third operational amplifier U3; The OUTA pin of the third operational amplifier U3 is connected to the +INB pin of the third operational amplifier U3 through the second balancing resistor R2; The V- pin of the third operational amplifier U3 is connected to the -5V power supply; The V+ pin of the third operational amplifier U3 is connected to the +5V power supply; The V- pin of the third operational amplifier U3 is connected to one end of the first capacitor C1; The V+ pin of the third operational amplifier U3 is connected to one end of the second capacitor C2; The other end of the first capacitor C1 is connected to the other end of the second capacitor C2; The other end of the first capacitor C1 and the other end of the second capacitor C2 are grounded; The -INB pin of the third operational amplifier U3 is connected to one end of the third resistor R3; The -INB pin of the third operational amplifier U3 is connected to one end of the fourth resistor R4; The OUTB pin of the third operational amplifier U3 is connected to the other end of the third resistor R3; The OUTB pin of the third operational amplifier U3 is connected to one end of the fifth resistor R5; The other end of the fifth resistor R5 is connected to one end of the third capacitor C3; The other end of the third capacitor C3 is connected to one end of the sixth resistor R6; The other end of the third capacitor C3 is connected to one end of the fourth capacitor C4; The other end of the sixth resistor R6 is connected to the other end of the fourth capacitor C4; The other end of the third capacitor C3 is grounded; The other end of the sixth resistor R6 is connected to the cathode of the first diode D1; The other end of the sixth resistor R6 is connected to the anode of the second diode D2; The other end of the fifth resistor R5 is connected to the anode of the first diode D1; The other end of the fifth resistor R5 is connected to the cathode of the second diode D2; The other end of the fifth resistor R5 is connected to the IA_P pin of the metering chip U2; The other end of the sixth resistor R6 is connected to the IA_N pin of the metering chip U2; The two input terminals of the second current transformer T2 are respectively connected to the B-phase terminal and the ground terminal of the three-phase power; The output terminal of the second current transformer T2 is respectively connected to one end of the third bead FB3 and the fourth bead FB4; The other ends of the third bead FB3 and the fourth bead FB4 are connected through the second transient voltage suppressor diode TVS2; The other end of the fourth bead FB4 is grounded; The other end of the third bead FB3 is grounded through the seventh sampling resistor R7; The other end of the third bead FB3 is connected to the +INA pin of the fourth operational amplifier U4; The -INA pin of the fourth operational amplifier U4 is connected to the OUTA pin of the fourth operational amplifier U4; The OUTA pin of the fourth operational amplifier U4 is connected to the +INB pin of the fourth operational amplifier U4 through the eighth balancing resistor R8; The V- pin of the fourth operational amplifier U4 is connected to the -5V power supply; The V+ pin of the fourth operational amplifier U4 is connected to the +5V power supply; The V- pin of the fourth operational amplifier U4 is connected to one end of the fifth capacitor C5; The V+ pin of the fourth operational amplifier U4 is connected to one end of the sixth capacitor C6; The other end of the fifth capacitor C5 is connected to the other end of the sixth capacitor C6; The other end of the fifth capacitor C5 and the other end of the sixth capacitor C6 are grounded; The -INB pin of the fourth operational amplifier U4 is connected to one end of the ninth resistor R9; The -INB pin of the fourth operational amplifier U4 is connected to one end of the tenth resistor R10; The OUTB pin of the fourth operational amplifier U4 is connected to the other end of the ninth resistor R9; The OUTB pin of the fourth operational amplifier U4 is connected to one end of the eleventh resistor R11; The other end of the eleventh resistor R11 is connected to one end of the seventh capacitor C7; The other end of the eleventh capacitor C11 is connected to one end of the twelfth resistor R12; The other end of the eleventh capacitor C11 is connected to one end of the eighth capacitor C8; The other end of the twelfth resistor R12 is connected to the other end of the eighth capacitor C8; The other end of the seventh capacitor C7 is grounded; The other end of the twelfth resistor R12 is connected to the cathode of the third diode D3; The other end of the twelfth resistor R12 is connected to the anode of the fourth diode D4; The other end of the eleventh resistor R11 is connected to the anode of the third diode D3; The other end of the eleventh resistor R11 is connected to the cathode of the fourth diode D4; The other end of the eleventh resistor R11 is connected to the pin IB_P of the metering chip U2; The other end of the twelfth resistor R12 is connected to the pin IB_N of the metering chip U2; The two input ends of the third current transformer T3 are respectively connected to the C-phase terminal of the three-phase power and the ground terminal; The output terminals of the third current transformer T3 are respectively connected to one ends of the fifth magnetic bead FB5 and the sixth magnetic bead FB6; The other ends of the fifth magnetic bead FB5 and the sixth magnetic bead FB6 are connected through the third transient voltage suppression diode TVS3; The other end of the sixth magnetic bead FB6 is grounded; The other end of the fifth magnetic bead FB5 is grounded through the thirteenth sampling resistor R13; The other end of the first magnetic bead FB1 is connected to the +INA pin of the fifth operational amplifier U5; The -INA pin of the fifth operational amplifier U5 is connected to the OUTA pin of the third operational amplifier U3; The OUTA pin of the fifth operational amplifier U5 is connected to the +INB pin of the fifth operational amplifier U5 through the fourteenth balancing resistor R14; The V- pin of the fifth operational amplifier U3 is connected to the -5V power supply; The V+ pin of the fifth operational amplifier U3 is connected to the +5V power supply; The V- pin of the fifth operational amplifier U3 is connected to one end of the ninth capacitor C9; The V+ pin of the fifth operational amplifier U3 is connected to one end of the tenth capacitor C10; The other end of the ninth capacitor C9 is connected to the other end of the tenth capacitor C10; The other end of the ninth capacitor C9 and the other end of the tenth capacitor C10 are grounded; The -INB pin of the fifth operational amplifier U5 is connected to one end of the fifteenth resistor R15; The -INB pin of the fifth operational amplifier U5 is connected to one end of the sixteenth resistor R16; The OUTB pin of the fifth operational amplifier U5 is connected to the other end of the fifteenth resistor R15; The OUTB pin of the fifth operational amplifier U5 is connected to one end of the seventeenth resistor R17; The other end of the seventeenth resistor R17 is connected to one end of the eleventh capacitor C11; The other end of the eleventh capacitor C11 is connected to one end of the eighteenth resistor R18; The other end of the eleventh capacitor C11 is connected to one end of the twelfth capacitor C12; The other end of the eighteenth resistor R18 is connected to the other end of the twelfth capacitor C12; The other end of the twelfth capacitor C12 is grounded; The other end of the seventeenth resistor R17 is connected to the cathode of the fifth diode D5; The other end of the eighteenth resistor R18 is connected to the anode of the fifth diode D5; The other end of the seventeenth resistor R17 is connected to the anode of the sixth diode D6; The other end of the eighteenth resistor R18 is connected to the cathode of the sixth diode D6; The other end of the seventeenth resistor R17 is connected to the Ic_P pin of the metering chip U2; The other end of the eighteenth resistor R18 is connected to the Ic_N pin of the metering chip U2; The SDI pin of the metering chip U2 is connected to the PC1 pin of the first chip U1; The SCS_N pin of the metering chip U2 is connected to the PB1 pin of the first chip U1; The SCLK pin of the metering chip U2 is connected to the PC2 pin of the first chip U1; The SDO pin of the metering chip U2 is connected to the PB2 pin of the first chip U1; The SDI pin of the metering chip U2 is connected to one end of the thirteenth capacitor C13; The other end of the thirteenth capacitor C13 is grounded; One end of the thirteenth capacitor C13 is connected to the SCS_N pin of the metering chip U2 through the fourteenth capacitor C14; The SDI pin of the metering chip U2 is connected to the power supply VCC through the nineteenth resistor R19; The SCS_N pin of the metering chip U2 is connected to the power supply VCC through the twentieth resistor R20; The SCLK pin of the metering chip U2 is grounded through the sixteenth capacitor C16; The SDO pin of the metering chip U2 is grounded through the fifteenth capacitor C15; The SDO pin of the metering chip U2 is connected to the power supply VCC through the twenty - first resistor R21.

[0009] The SCLK pin of the metering chip U2 is connected to the power supply VCC through the twenty - second resistor R22.

[0010] A control method for the three - phase three - wire current acquisition circuit of the adaptation network - matching terminal, the control process is as follows: When the network - matching terminal device applies this circuit and connects the network - matching terminal device to the measured circuit; The first current transformer T1, the second current transformer T2, and the third current transformer T3 in the current acquisition circuit respectively convert the three - phase currents of A, B, and C into small current signals that the subsequent circuit can process; the signals respectively pass through the corresponding beads and transient voltage suppression diodes, filter out high - frequency noise, and then pass through the sampling first resistor R1, the seventh resistor R7, and the thirteenth resistor R13 connected in parallel in the circuit. Using the parallel voltage - division characteristic, the current signal is converted into a voltage signal; The signal amplification circuit uses an amplification circuit composed of an operational amplifier and resistive devices to amplify the voltage signal from the current acquisition circuit by 5 times, and the common-mode capacitance of this part of the circuit can effectively suppress common-mode noise. When the amplified voltage signal flows through the bidirectional limiting circuit composed of the first diode D1 and the second diode D2, the third diode D3 and the fourth diode D4, and the fifth diode D5 and the sixth diode D6, the amplitude of the voltage signal is clamped between -1.25V and 1.25V; After receiving the voltage signal from the amplification circuit, the power metering chip U2 of the metering and processing circuit calculates the magnitudes of the currents of the three phases A, B, and C of the measured circuit according to a preset calculation method, and transmits the calculated data to the MCU through the SPI bus to realize the reprocessing of the data, and then completes the acquisition and processing of the currents of the three phases A, B, and C.

[0011] Advantages of the present invention over the prior art: The three-phase three-wire current acquisition circuit of the present invention adapted to the distribution network terminal includes a current acquisition circuit, a signal amplification circuit, and a metering and processing circuit. It adopts a high-precision power metering chip, an operational amplifier, and a multi-stage anti-interference design. Through components such as a current transformer, a magnetic bead, a transient voltage suppression diode TVS, and a sampling resistor, it realizes the conversion from a large current to a small current and the conversion from a current signal to a voltage signal, and effectively suppresses electromagnetic interference and high-frequency noise; through components such as an operational amplifier, resistors, capacitors, and diodes, it realizes the acquisition of current signals and improves the accuracy and amplitude of the signals; through components such as a power metering chip, an MCU, resistors, and capacitors, it realizes data storage, processing, and communication. Through multi-level signal processing and anti-interference design, it significantly improves the accuracy and reliability of current acquisition, can effectively meet the application requirements in a complex electromagnetic environment, and provides high-quality current data support for distribution network terminal equipment; the design of the present invention can be widely applied to distribution network terminal units (such as DTUs, FTUs, etc.) and power management systems, and can complete the task of accurate current acquisition in a complex electromagnetic environment. Description of the drawings

[0012] Figure 1 is a schematic diagram of the architecture of the three-phase three-wire current acquisition circuit of the present invention adapted to the distribution network terminal; Figure 2 is the circuit schematic diagram of the three-phase three-wire current acquisition circuit of the present invention adapted to the distribution network terminal. Detailed implementation manners

[0013] The present invention will be described in detail below with reference to the drawings and embodiments: Attached Figure 1 and 2 It can be seen that a three-phase three-wire current acquisition circuit adapted to the distribution network terminal, The two input terminals of the first current transformer T1 are respectively connected to the A-phase terminal and the ground terminal of the three-phase power supply; The output terminals of the first current transformer T1 are respectively connected to one ends of the first magnetic bead FB1 and the second magnetic bead FB2; The other ends of the first magnetic bead FB1 and the second magnetic bead FB2 are connected through the first transient voltage suppression diode TVS1; The other end of the second magnetic bead FB2 is grounded; The other end of the first magnetic bead FB1 is grounded through the first sampling resistor R1; The other end of the first magnetic bead FB1 is connected to the +INA pin of the third operational amplifier U3; The -INA pin of the third operational amplifier U3 is connected to the OUTA pin of the third operational amplifier U3; The OUTA pin of the third operational amplifier U3 is connected to the +INB pin of the third operational amplifier U3 through the second balancing resistor R2; The V- pin of the third operational amplifier U3 is connected to the -5V power supply; The V+ pin of the third operational amplifier U3 is connected to the +5V power supply; The V- pin of the third operational amplifier U3 is connected to one end of the first capacitor C1; The V+ pin of the third operational amplifier U3 is connected to one end of the second capacitor C2; The other end of the first capacitor C1 is connected to the other end of the second capacitor C2; The other ends of the first capacitor C1 and the second capacitor C2 are grounded; The -INB pin of the third operational amplifier U3 is connected to one end of the third resistor R3; The -INB pin of the third operational amplifier U3 is connected to one end of the fourth resistor R4; The OUTB pin of the third operational amplifier U3 is connected to the other end of the third resistor R3; The OUTB pin of the third operational amplifier U3 is connected to one end of the fifth resistor R5; The other end of the fifth resistor R5 is connected to one end of the third capacitor C3; The other end of the third capacitor C3 is connected to one end of the sixth resistor R6; The other end of the third capacitor C3 is connected to one end of the fourth capacitor C4; The other end of the sixth resistor R6 is connected to the other end of the fourth capacitor C4; The other end of the third capacitor C3 is grounded; The other end of the sixth resistor R6 is connected to the cathode of the first diode D1; The other end of the sixth resistor R6 is connected to the anode of the second diode D2; The other end of the fifth resistor R5 is connected to the anode of the first diode D1; The other end of the fifth resistor R5 is connected to the cathode of the second diode D2; The other end of the fifth resistor R5 is connected to the pin IA_P of the metering chip U2; The other end of the sixth resistor R6 is connected to the pin IA_N of the metering chip U2; The two input ends of the second current transformer T2 are respectively connected to the B-phase terminal and the ground terminal of the three-phase power; The output end of the second current transformer T2 is respectively connected to one end of the third bead FB3 and the fourth bead FB4; The other ends of the third bead FB3 and the fourth bead FB4 are connected through the second transient voltage suppression diode TVS2; The other end of the fourth bead FB4 is grounded; The other end of the third bead FB3 is grounded through the seventh sampling resistor R7; The other end of the third bead FB3 is connected to the +INA pin of the fourth operational amplifier U4; The -INA pin of the fourth operational amplifier U4 is connected to the OUTA pin of the fourth operational amplifier U4; The OUTA pin of the fourth operational amplifier U4 is connected to the +INB pin of the fourth operational amplifier U4 through the eighth balancing resistor R8; The V- pin of the fourth operational amplifier U4 is connected to the -5V power supply; The V+ pin of the fourth operational amplifier U4 is connected to the +5V power supply; The V- pin of the fourth operational amplifier U4 is connected to one end of the fifth capacitor C5; The V+ pin of the fourth operational amplifier U4 is connected to one end of the sixth capacitor C6; The other end of the fifth capacitor C5 is connected to the other end of the sixth capacitor C6; The other ends of the fifth capacitor C5 and the sixth capacitor C6 are grounded; The -INB pin of the fourth operational amplifier U4 is connected to one end of the ninth resistor R9; The -INB pin of the fourth operational amplifier U4 is connected to one end of the tenth resistor R10; The OUTB pin of the fourth operational amplifier U4 is connected to the other end of the ninth resistor R9; The OUTB pin of the fourth operational amplifier U4 is connected to one end of the eleventh resistor R11; The other end of the eleventh resistor R11 is connected to one end of the seventh capacitor C7; The other end of the eleventh capacitor C11 is connected to one end of the twelfth resistor R12; The other end of the eleventh capacitor C11 is connected to one end of the eighth capacitor C8; The other end of the twelfth resistor R12 is connected to the other end of the eighth capacitor C8; The other end of the seventh capacitor C7 is grounded; The other end of the twelfth resistor R12 is connected to the cathode of the third diode D3; The other end of the twelfth resistor R12 is connected to the anode of the fourth diode D4; The other end of the eleventh resistor R11 is connected to the anode of the third diode D3; The other end of the eleventh resistor R11 is connected to the cathode of the fourth diode D4; The other end of the eleventh resistor R11 is connected to the pin IB_P of the metering chip U2; The other end of the twelfth resistor R12 is connected to the pin IB_N of the metering chip U2; The two input ends of the third current transformer T3 are respectively connected to the C-phase terminal of the three-phase power and the ground terminal; The output end of the third current transformer T3 is respectively connected to one end of the fifth bead FB5 and the sixth bead FB6; The other ends of the fifth bead FB5 and the sixth bead FB6 are connected through the third transient voltage suppressor diode TVS3; The other end of the sixth bead FB6 is grounded; The other end of the fifth bead FB5 is grounded through the thirteenth sampling resistor R13; The other end of the first bead FB1 is connected to the +INA pin of the fifth operational amplifier U5; The -INA pin of the fifth operational amplifier U5 is connected to the OUTA pin of the third operational amplifier U3; The OUTA pin of the fifth operational amplifier U5 is connected to the +INB pin of the fifth operational amplifier U5 through the fourteenth balancing resistor R14; The V- pin of the fifth operational amplifier U3 is connected to the -5V power supply; The V+ pin of the fifth operational amplifier U3 is connected to the +5V power supply; The V- pin of the fifth operational amplifier U3 is connected to one end of the ninth capacitor C9; The V+ pin of the fifth operational amplifier U3 is connected to one end of the tenth capacitor C10; The other end of the ninth capacitor C9 is connected to the other end of the tenth capacitor C10; The other end of the ninth capacitor C9 and the other end of the tenth capacitor C10 are grounded; The -INB pin of the fifth operational amplifier U5 is connected to one end of the fifteenth resistor R15; The -INB pin of the fifth operational amplifier U5 is connected to one end of the sixteenth resistor R16; The OUTB pin of the fifth operational amplifier U5 is connected to the other end of the fifteenth resistor R15; The OUTB pin of the fifth operational amplifier U5 is connected to one end of the seventeenth resistor R17; The other end of the seventeenth resistor R17 is connected to one end of the eleventh capacitor C11; The other end of the eleventh capacitor C11 is connected to one end of the eighteenth resistor R18; The other end of the eleventh capacitor C11 is connected to one end of the twelfth capacitor C12; The other end of the eighteenth resistor R18 is connected to the other end of the twelfth capacitor C12; The other end of the twelfth capacitor C12 is grounded; The other end of the seventeenth resistor R17 is connected to the cathode of the fifth diode D5; The other end of the eighteenth resistor R18 is connected to the anode of the fifth diode D5; The other end of the seventeenth resistor R17 is connected to the anode of the sixth diode D6; The other end of the eighteenth resistor R18 is connected to the cathode of the sixth diode D6; The other end of the seventeenth resistor R17 is connected to the Ic_P pin of the metering chip U2; The other end of the eighteenth resistor R18 is connected to the Ic_N pin of the metering chip U2; The SDI pin of the metering chip U2 is connected to the PC1 pin of the first chip U1; The SCS_N pin of the metering chip U2 is connected to the PB1 pin of the first chip U1; The SCLK pin of the metering chip U2 is connected to the PC2 pin of the first chip U1; The SDO pin of the metering chip U2 is connected to the PB2 pin of the first chip U1; The SDI pin of the metering chip U2 is connected to one end of the thirteenth capacitor C13; The other end of the thirteenth capacitor C13 is grounded; One end of the thirteenth capacitor C13 is connected to the SCS_N pin of the metering chip U2 through the fourteenth capacitor C14; The SDI pin of the metering chip U2 is connected to the power supply VCC through the nineteenth resistor R19; The SCS_N pin of the metering chip U2 is connected to the power supply VCC through the twentieth resistor R20; The SCLK pin of the metering chip U2 is grounded through the sixteenth capacitor C16; The SDO pin of the metering chip U2 is grounded through the fifteenth capacitor C15; The SDO pin of the metering chip U2 is connected to the power supply VCC through the twenty-first resistor R21.

[0014] The SCLK pin of the metering chip U2 is connected to the power supply VCC through the twenty-second resistor R22.

[0015] A control method for a three-phase three-wire current acquisition circuit of an adapter power distribution network terminal, the control process is as follows: When the power distribution network terminal device applies this circuit and connects the power distribution network terminal device to the circuit under test; The first current transformer T1, the second current transformer T2, and the third current transformer T3 in the current acquisition circuit respectively convert the three-phase currents of phases A, B, and C into small current signals that the subsequent circuit can process; the signals respectively pass through the corresponding beads and transient voltage suppression diodes, and after filtering out high-frequency noise, they pass through the sampling first resistor R1, the seventh resistor R7, and the thirteenth resistor R13 connected in parallel in the circuit. Using the parallel voltage division characteristic, the current signal is converted into a voltage signal; The signal amplification circuit uses an amplification circuit composed of an operational amplifier and resistor devices to amplify the voltage signal from the current acquisition circuit by 5 times, and the common-mode capacitor of this part of the circuit can effectively suppress common-mode noise. When the amplified voltage signal flows through the bidirectional limiting circuit composed of the first diode D1 and the second diode D2, the third diode D3 and the fourth diode D4, and the fifth diode D5 and the sixth diode D6, the amplitude of the voltage signal is clamped between -1.25V and 1.25; After receiving the voltage signal from the amplification circuit, the power metering chip U2 of the metering and processing circuit calculates the magnitudes of the three-phase currents of phases A, B, and C of the circuit under test according to a preset calculation method, and transmits the calculated data to the MCU through the SPI bus to realize the reprocessing of the data, and then complete the acquisition and processing of the three-phase currents of phases A, B, and C.

[0016] The detailed description of each part of the circuit is as follows: The current acquisition circuit consists of current transformers, beads, transient voltage suppression diodes, and sampling resistors. When the distribution network terminal device uses the circuit designed by the present invention to acquire the current of the power supply network, the current transformers T1, T2, and T3 respectively convert the currents of the three phases A, B, and C into small current signals suitable for acquisition. After the small current signal flows through the output of the current transformer, the inherent resistance characteristics of the beads FB1 and FB2, FB3 and FB4, FB5 and FB6 are used to suppress the high-frequency noise in the current signals of the three phases A, B, and C, especially the high-frequency signals caused by external electromagnetic interference, so as to improve the quality of the current signal. The transient voltage suppression diodes TVS1, TVS2, and TVS3 connected in parallel in the circuit can quickly respond to the instantaneous change of the external voltage and ensure that the subsequent circuit is not damaged by the voltage mutation. One end of the sampling resistors R1, R7, and R13 is connected to the acquisition circuit and the other end is grounded. By means of voltage division, the current signal in the circuit is converted into a voltage signal.

[0017] Exemplarily, the current transformers T1, T2, and T3 can be current transformers with a rated input current of 5A, a rated output current of 2.5mA, and a turns ratio of 1:2000. Exemplarily, the beads FB1, FB2, FB3, FB4, FB5, and FB6 can be beads with an impedance @ frequency of 600Ω @ 100MHz and a maximum DC resistance of 380mA. Exemplarily, the transient voltage suppression diodes TVS1, TVS2, and TVS3 can be transient voltage suppression diodes with a reverse cut-off voltage of 6.5V, a clamping voltage of 11.2V, and a breakdown voltage of 7.22V. Exemplarily, the resistors R1, R7, and R13 can be sampling resistors with a resistance value of 130Ω and a temperature coefficient of ±10ppm / ℃. The signal amplification circuit consists of components such as operational amplifiers, resistors, capacitors, and diodes. The operational amplifiers U3, U4, and U5 are dual-channel operational amplifiers. One channel is used as a follower, and the output is connected to the output of the second channel to play an isolation role. The other channel respectively forms an amplification circuit with a magnification ratio of 5 with the resistors R3 and R4, R9 and R10, R15 and R16, and balancing resistors R2, R8, and R14 are configured. The capacitors C1 and C2, C5 and C6, C9 and C10 are filter capacitors for the positive and negative power supply inputs of the operational amplifiers U3, U4, and U5, aiming to reduce high-frequency external interference.

[0018] Resistors R5 and R6, R11 and R12, R17 and R18 are the current-limiting resistors of the A, B, and C phase acquisition circuits respectively. One end of R5, R11, and R17 is connected to the output terminals of operational amplifiers U3, U4, and U5 respectively, and the other end is connected to the IA_P, IB_P, and IC_P pins of the power metering chip; one end of R6, R12, and R18 is grounded, and the other end is connected to the IA_N, IB_N, and IC_N pins of the power metering chip respectively; Capacitors C3 and C4, C7 and C8, C11 and C12 are common-mode capacitors, aiming to suppress common-mode noise; Diodes D1 and D2, D3 and D4, D5 and D6 form a bidirectional limiting circuit to ensure that no matter how large the voltage is before the diode, the voltage on the power metering chip is always between -1.25V and 1.25V, playing a role in protecting the power metering chip.

[0019] Exemplarily, operational amplifiers U3, U4, and U5 can select an amplifier with two channels, a maximum power supply width of 36V, and a gain-bandwidth product of 8MHz. Exemplarily, resistors R3, R9, and R15 can select resistors with a resistance value of 40kΩ, R4, R10, and R16 can select resistors with a resistance value of 10kΩ, and resistors R2, R8, and R14 can select resistors with a resistance value of 10kΩ.

[0020] Exemplarily, resistors R5, R6, R11, R12, R17, and R18 can select resistors with a resistance value of 1kΩ; Exemplarily, capacitors C3, C4, C7, C8, C11, and C12 can select capacitors with a capacitance value of 33nF; Exemplarily, diodes D1, D2, D3, D4, D5, and D6 can select switching diodes with a forward voltage drop of 1.25V@150mA and a DC reverse breakdown voltage of 75V. The metering and processing circuit consists of a power metering chip, an MCU, resistors, and capacitors. The IA_P and IA_N, IB_P and IB_N, IC_P and IC_N pins of the metering chip receive the voltage signals amplified by the signal amplification circuit, and calculate the magnitudes of the A, B, and C phase currents according to a preset calculation method, and transmit the calculated current data to the MCU through the SPI bus communication method for further processing of the current data. In the SPI bus communication method, SDI is the data output of the power metering chip, and the MCU receives the data; SCS_N is the chip select signal line; SCLK is the clock signal line for communication synchronization; SDO is the data output from the MCU to the power metering chip.

[0021] Resistors R19, R20, R21, and R22 are pull-up resistors on the SPI communication line, used to maintain the voltage of the signal line and improve the stability of data transmission; capacitors C13, C14, C15, and C16 are filter capacitors to avoid affecting the clarity of data transmission.

[0022] Exemplarily, the electric energy metering chip U2 can select a high-precision three-phase electric energy chip that meets the requirements of 0.5S and 0.2S active energy meters of the State Grid; Exemplarily, U1 can select a high-performance microcontroller with rich peripherals and interfaces, suitable for multiple application scenarios, and having powerful computing capabilities; Exemplarily, resistors R19, R20, R21, and R22 can select resistors with a resistance value of 10 kΩ; Exemplarily, capacitors C13, C14, C15, and C16 can select capacitors with a capacitance value of 10 pF.

[0023] From the above technical solutions, it can be seen that the present invention is applicable to the following scenarios: This current acquisition circuit is particularly applicable to intelligent distribution networks, energy management systems, and power monitoring and optimal dispatching systems. In these application scenarios, the circuit can provide high-precision and high-reliability current data for various distribution network terminal devices, supporting the system to perform tasks such as intelligent decision-making, load forecasting, fault detection, and automated dispatching. Through these real-time data, the distribution network can perform more accurate energy management, improve the overall operation efficiency, and ensure the stability and reliability of power supply.

[0024] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the structure of the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention all fall within the scope of the technical solutions of the present invention.

Claims

1. A three-phase three-wire current acquisition circuit adapted to a network configuration terminal, characterized in that: Two input terminals of the first current transformer T1 are respectively connected to the A-phase terminal and the ground terminal of the three-phase power supply; The output terminal of the first current transformer T1 is respectively connected to one end of the first magnetic bead FB1 and the second magnetic bead FB2; The other ends of the first magnetic bead FB1 and the second magnetic bead FB2 are connected through the first transient voltage suppression diode TVS1; The other end of the second magnetic bead FB2 is grounded; The other end of the first magnetic bead FB1 is grounded through the first sampling resistor R1; The other end of the first magnetic bead FB1 is connected to the +INA pin of the third operational amplifier U3; The -INA pin of the third operational amplifier U3 is connected to the OUTA pin of the third operational amplifier U3; The OUTA pin of the third operational amplifier U3 is connected to the +INB pin of the third operational amplifier U3 through the second balancing resistor R2; The V- pin of the third operational amplifier U3 is connected to the -5V power supply; The V+ pin of the third operational amplifier U3 is connected to the +5V power supply; The V- pin of the third operational amplifier U3 is connected to one end of the first capacitor C1; The V+ pin of the third operational amplifier U3 is connected to one end of the second capacitor C2; The other end of the first capacitor C1 is connected to the other end of the second capacitor C2; The other end of the first capacitor C1 and the other end of the second capacitor C2 are grounded; The -INB pin of the third operational amplifier U3 is connected to one end of the third resistor R3; The -INB pin of the third operational amplifier U3 is connected to one end of the fourth resistor R4; The OUTB pin of the third operational amplifier U3 is connected to the other end of the third resistor R3; The OUTB pin of the third operational amplifier U3 is connected to one end of the fifth resistor R5; The other end of the fifth resistor R5 is connected to one end of the third capacitor C3; The other end of the third capacitor C3 is connected to one end of the sixth resistor R6; The other end of the third capacitor C3 is connected to one end of the fourth capacitor C4; The other end of the sixth resistor R6 is connected to the other end of the fourth capacitor C4; The other end of the third capacitor C3 is grounded; The other end of the sixth resistor R6 is connected to the cathode of the first diode D1; The other end of the sixth resistor R6 is connected to the anode of the second diode D2; The other end of the fifth resistor R5 is connected to the anode of the first diode D1; The other end of the fifth resistor R5 is connected to the cathode of the second diode D2; The other end of the fifth resistor R5 is connected to the IA_P pin of the metering chip U2; The other end of the sixth resistor R6 is connected to the IA_N pin of the metering chip U2; Two input terminals of the second current transformer T2 are respectively connected to the B-phase terminal and the ground terminal of the three-phase power supply; The output terminal of the second current transformer T2 is respectively connected to one end of the third magnetic bead FB3 and the fourth magnetic bead FB4; The other ends of the third magnetic bead FB3 and the fourth magnetic bead FB4 are connected through the second transient voltage suppression diode TVS2; The other end of the fourth magnetic bead FB4 is grounded; The other end of the third magnetic bead FB3 is grounded through the seventh sampling resistor R7; The other end of the third magnetic bead FB3 is connected to the +INA pin of the fourth operational amplifier U4; The -INA pin of the fourth operational amplifier U4 is connected to the OUTA pin of the fourth operational amplifier U4; The OUTA pin of the fourth operational amplifier U4 is connected to the +INB pin of the fourth operational amplifier U4 through the eighth balancing resistor R8; The V- pin of the fourth operational amplifier U4 is connected to the -5V power supply; The V+ pin of the fourth operational amplifier U4 is connected to the +5V power supply; The V- pin of the fourth operational amplifier U4 is connected to one end of the fifth capacitor C5; The V+ pin of the fourth operational amplifier U4 is connected to one end of the sixth capacitor C6; The other end of the fifth capacitor C5 is connected to the other end of the sixth capacitor C6; The other end of the fifth capacitor C5 and the other end of the sixth capacitor C6 are grounded; The -INB pin of the fourth operational amplifier U4 is connected to one end of the ninth resistor R9; The -INB pin of the fourth operational amplifier U4 is connected to one end of the tenth resistor R10; The OUTB pin of the fourth operational amplifier U4 is connected to the other end of the ninth resistor R9; The OUTB pin of the fourth operational amplifier U4 is connected to one end of the eleventh resistor R11; The other end of the eleventh resistor R11 is connected to one end of the seventh capacitor C7; The other end of the eleventh capacitor C11 is connected to one end of the twelfth resistor R12; The other end of the eleventh capacitor C11 is connected to one end of the eighth capacitor C8; The other end of the twelfth resistor R12 is connected to the other end of the eighth capacitor C8; The other end of the seventh capacitor C7 is grounded; The other end of the twelfth resistor R12 is connected to the cathode of the third diode D3; The other end of the twelfth resistor R12 is connected to the anode of the fourth diode D4; The other end of the eleventh resistor R11 is connected to the anode of the third diode D3; The other end of the eleventh resistor R11 is connected to the cathode of the fourth diode D4; The other end of the eleventh resistor R11 is connected to the IB_P pin of the metering chip U2; The other end of the twelfth resistor R12 is connected to the IB_N pin of the metering chip U2; The two input terminals of the third current transformer T3 are respectively connected to the C-phase terminal and the ground terminal of the three-phase power; The output terminal of the third current transformer T3 is respectively connected to one end of the fifth bead FB5 and the sixth bead FB6; The other ends of the fifth bead FB5 and the sixth bead FB6 are connected through the third transient voltage suppression diode TVS3; The other end of the sixth bead FB6 is grounded; The other end of the fifth bead FB5 is grounded through the thirteenth sampling resistor R13; The other end of the first bead FB1 is connected to the +INA pin of the fifth operational amplifier U5; The -INA pin of the fifth operational amplifier U5 is connected to the OUTA pin of the third operational amplifier U3; The OUTA pin of the fifth operational amplifier U5 is connected to the +INB pin of the fifth operational amplifier U5 through the fourteenth balancing resistor R14; The V- pin of the fifth operational amplifier U3 is connected to the -5V power supply; The V+ pin of the fifth operational amplifier U3 is connected to the +5V power supply; The V- pin of the fifth operational amplifier U3 is connected to one end of the ninth capacitor C9; The V+ pin of the fifth operational amplifier U3 is connected to one end of the tenth capacitor C10; The other end of the ninth capacitor C9 is connected to the other end of the tenth capacitor C10; The other end of the ninth capacitor C9 and the other end of the tenth capacitor C10 are grounded; The -INB pin of the fifth operational amplifier U5 is connected to one end of the fifteenth resistor R15; The -INB pin of the fifth operational amplifier U5 is connected to one end of the sixteenth resistor R16; The OUTB pin of the fifth operational amplifier U5 is connected to the other end of the fifteenth resistor R15; The OUTB pin of the fifth operational amplifier U5 is connected to one end of the seventeenth resistor R17; The other end of the seventeenth resistor R17 is connected to one end of the eleventh capacitor C11; The other end of the eleventh capacitor C11 is connected to one end of the eighteenth resistor R18; The other end of the eleventh capacitor C11 is connected to one end of the twelfth capacitor C12; The other end of the eighteenth resistor R18 is connected to the other end of the twelfth capacitor C12; The other end of the twelfth capacitor C12 is grounded; The other end of the seventeenth resistor R17 is connected to the cathode of the fifth diode D5; The other end of the eighteenth resistor R18 is connected to the anode of the fifth diode D5; The other end of the seventeenth resistor R17 is connected to the anode of the sixth diode D6; The other end of the eighteenth resistor R18 is connected to the cathode of the sixth diode D6; The other end of the seventeenth resistor R17 is connected to the Ic_P pin of the metering chip U2; The other end of the eighteenth resistor R18 is connected to the Ic_N pin of the metering chip U2; The SDI pin of the metering chip U2 is connected to the PC1 pin of the first chip U1; The SCS_N pin of the metering chip U2 is connected to the PB1 pin of the first chip U1; The SCLK pin of the metering chip U2 is connected to the PC2 pin of the first chip U1; The SDO pin of the metering chip U2 is connected to the PB2 pin of the first chip U1; The SDI pin of the metering chip U2 is connected to one end of the thirteenth capacitor C13; The other end of the thirteenth capacitor C13 is grounded; One end of the thirteenth capacitor C13 is connected to the SCS_N pin of the metering chip U2 through the fourteenth capacitor C14; The SDI pin of the metering chip U2 is connected to the power supply VCC through the nineteenth resistor R19; The SCS_N pin of the metering chip U2 is connected to the power supply VCC through the twentieth resistor R20; The SCLK pin of the metering chip U2 is grounded through the sixteenth capacitor C16; The SDO pin of the metering chip U2 is grounded through the fifteenth capacitor C15; The SDO pin of the metering chip U2 is connected to the power supply VCC through the twenty-first resistor R21; The SCLK pin of the metering chip U2 is connected to the power supply VCC through the twenty-second resistor R22.

2. The control method of the three-phase three-wire current acquisition circuit for the adapted network terminal according to claim 1, characterized in that, The control process is as follows: The first current transformer T1, the second current transformer T2, and the third current transformer T3 in the current acquisition circuit respectively convert the three-phase currents of A, B, and C into small current signals that can be processed by the subsequent circuit; after the signals pass through the corresponding beads and transient voltage suppression diodes respectively to filter out high-frequency noise, they pass through the sampling first resistor R1, the seventh resistor R7, and the thirteenth resistor R13 connected in parallel in the circuit. Using the parallel voltage division characteristic, the current signal is converted into a voltage signal; The signal amplification circuit uses an amplification circuit composed of an operational amplifier and resistive devices to amplify the voltage signal from the current acquisition circuit by 5 times, and the common-mode capacitance of this part of the circuit can effectively suppress common-mode noise. When the amplified voltage signal flows through the bidirectional limiting circuit composed of the first diode D1 and the second diode D2, the third diode D3 and the fourth diode D4, and the fifth diode D5 and the sixth diode D6, the amplitude of the voltage signal is clamped between -1.25V and 1.25V; After receiving the voltage signal from the amplification circuit, the power metering chip U2 of the metering and processing circuit calculates the magnitudes of the currents of the three phases A, B, and C of the measured circuit according to a preset calculation method, and transmits the calculated data to the MCU through the SPI bus to realize the reprocessing of the data, and then complete the acquisition and processing of the currents of the three phases A, B, and C.

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