Current sampling circuit, current sampling equipment and power distribution automation system

Abstract

The invention is suitable for the field of power distribution automation systems, and provides a current sampling circuit, a current sampling device and a power distribution automation system.The current sampling circuit comprises a signal collecting and uploading module, a plurality of signal conversion modules and a plurality of signal processing modules, and the signal conversion modules are in one-to-one correspondence with a plurality of transmission lines; each signal conversion module is connected in series with the corresponding transmission line, the plurality of signal conversion modules and the plurality of signal processing modules are in one-to-one correspondence, each signal conversion module is electrically connected with the corresponding signal processing module, and all the signal processing modules are electrically connected with the signal acquisition and uploading module. According to the invention, the signal conversion module employs an electrical isolation design, and the collection of the first current signal and the output of the first voltage signal on the transmission line are electrically isolated, thereby greatly improving the electromagnetic compatibility of the circuit, and effectively improving the power supply reliability of the distribution network equipment.

Description

Technical Field

[0001] This application belongs to the field of power distribution automation systems, and particularly relates to a current sampling circuit, a current sampling device, and a power distribution automation system. Background Technology

[0002] With the development of smart grids, distribution automation terminals, as core components of the distribution network, work in conjunction with primary equipment to achieve reliable operation and fault isolation. Their monitoring of the opening and closing of circuit breakers and the energy storage current in primary equipment is of great significance. By monitoring the current of the electromagnetic coils of the drive mechanism, it is possible to predict whether the operation is normal, diagnose equipment lifespan and faults, analyze mechanical wear based on current waveforms, and assist in verifying the integrity of opening and closing. Energy storage current monitoring can determine the status of energy storage components and the built-in batteries and charging modules of the distribution terminal, and identify problems such as motor bearing wear. Currently, DC current acquisition often uses a shunt converter paired with a voltage and current monitor chip. This scheme detects the voltage difference across the shunt converter, converts it into current according to Ohm's law, and transmits it to the voltage and current monitor chip for processing. When applied to DC sampling in distribution network automation terminal equipment, although this scheme can achieve current acquisition, it suffers from the drawback of non-isolated circuits. During electromagnetic compatibility testing, the voltage and current monitor chip may be damaged. Summary of the Invention

[0003] This application provides a current sampling circuit, a current sampling device, and a power distribution automation system, which can solve the problem that the existing DC current acquisition scheme uses a shunt with a voltage and current monitor chip, and the circuit is not isolated, so the voltage and current monitor chip may be damaged during electromagnetic compatibility testing.

[0004] In a first aspect, embodiments of this application provide a current sampling circuit, including a signal acquisition and transmission module, multiple signal conversion modules, and multiple signal processing modules. The multiple signal conversion modules correspond one-to-one with multiple transmission lines, and each signal conversion module is connected in series with the corresponding transmission line. The multiple signal conversion modules correspond one-to-one with the multiple signal processing modules, and each signal conversion module is electrically connected to the corresponding signal processing module. All the signal processing modules are electrically connected to the signal acquisition and transmission module.

[0005] The signal conversion module is used to output a first voltage signal to the signal processing module based on a first current signal on the transmission line, the signal processing module is used to output a second voltage signal to the signal acquisition and uploading module based on the first voltage signal, and the signal acquisition and uploading module is used to output a target signal based on the second voltage signal.

[0006] In one possible implementation of the first aspect, the signal conversion module includes a Hall current sensor, and the first output pin and the second output pin of the Hall current sensor are both electrically connected to the corresponding signal processing module. The first output pin of the Hall current sensor is used to output the first voltage signal, and the second output pin of the Hall current sensor is used to output a reference voltage. The first current detection pin and the second current detection pin of the Hall current sensor are both connected in series on the corresponding transmission line.

[0007] In one possible implementation of the first aspect, the signal processing module includes an adjustment unit, a filtering unit, and a zero-drift suppression unit, wherein the adjustment unit, the filtering unit, and the zero-drift suppression unit are electrically connected in sequence, the adjustment unit is electrically connected to the corresponding signal conversion module, and the zero-drift suppression unit is electrically connected to the signal acquisition and transmission module.

[0008] The adjustment unit is used to output a first output signal to the filtering unit according to the first voltage signal. The filtering unit is used to filter out high-frequency signals in the first output signal and output the second voltage signal. The zero drift suppression unit is used to limit the zero drift of the second voltage signal within a preset range.

[0009] In one possible implementation of the first aspect, the adjustment unit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor, and a first operational amplifier. The first end of the first resistor and the first end of the second resistor are both electrically connected to the corresponding signal conversion module. The second end of the first resistor is electrically connected to the first end of the third resistor, the first end of the second capacitor, and the first input terminal of the first operational amplifier. The second end of the third resistor is electrically connected to the second end of the second capacitor, the output terminal of the first operational amplifier, and the filtering unit. The first end of the fourth resistor is electrically connected to the second end of the second resistor, the first end of the first capacitor, and the second input terminal of the first operational amplifier. The second end of the fourth resistor and the second end of the first capacitor are both grounded.

[0010] In one possible implementation of the first aspect, the filtering unit includes a fifth resistor and a third capacitor, the first end of the fifth resistor is electrically connected to the adjustment unit, the second end of the fifth resistor is electrically connected to the first end of the third capacitor and the zero drift suppression unit, and the second end of the third capacitor is grounded.

[0011] In one possible implementation of the first aspect, the zero-drift suppression unit includes a sixth resistor, the first end of which is electrically connected to the filtering unit and the signal acquisition and transmission module, and the second end of which is grounded.

[0012] In one possible implementation of the first aspect, the signal acquisition and transmission module includes a data conversion unit and a processor chip, wherein the data conversion unit is electrically connected to the processor chip and all of the signal processing modules respectively.

[0013] The data conversion unit is used to output a conversion signal to the processor chip according to the second voltage signal, and the processor chip is used to output the target signal according to the conversion signal.

[0014] In one possible implementation of the first aspect, the data conversion unit includes a seventh resistor, an eighth resistor, a fourth capacitor, and an analog-to-digital converter. The first end of the seventh resistor is electrically connected to all of the signal processing modules, the second end of the seventh resistor is electrically connected to the first end of the fourth capacitor and the first input terminal of the analog-to-digital converter, the first end of the eighth resistor is grounded, the second end of the eighth resistor is electrically connected to the second end of the fourth capacitor and the second input terminal of the analog-to-digital converter, and the output terminal of the analog-to-digital converter is electrically connected to the processor chip.

[0015] Secondly, embodiments of this application provide a current sampling device, including the current sampling circuit described in any one of the first aspects.

[0016] Thirdly, embodiments of this application provide a power distribution automation system, including a primary device and the current sampling device described in the second aspect, wherein the primary device and the current sampling device are electrically connected.

[0017] The beneficial effects of the embodiments in this application compared with the prior art are:

[0018] The current sampling circuit provided in this application includes a signal acquisition and transmission module, multiple signal conversion modules, and multiple signal processing modules. Each signal conversion module corresponds one-to-one with multiple transmission lines, and each module is connected in series with its corresponding transmission line to achieve real-time monitoring of the first current signal on the transmission line. Simultaneously, each signal conversion module is electrically connected to its corresponding signal processing module, and can output a first voltage signal to the signal processing module based on the first current signal on the transmission line, thereby converting the first current signal. Then, the signal processing module outputs a second voltage signal based on the first voltage signal, and the signal acquisition and transmission module outputs a target signal based on the second voltage signal. Therefore, the signal conversion module in this application employs an electrical isolation design, electrically isolating the acquisition of the first current signal from the output of the first voltage signal on the transmission line, greatly improving the electromagnetic compatibility performance of the current sampling circuit. Even if the signal conversion module fails, it will not affect the normal switching operation of the subsequent circuits controlled by the distribution network equipment, thus effectively improving the reliability of the power supply to the distribution network equipment. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic block diagram of a current sampling circuit provided in one embodiment of this application;

[0021] Figure 2 This is a circuit connection diagram of a signal conversion module provided in an embodiment of this application;

[0022] Figure 3 This is a schematic diagram of the internal circuit of a Hall current sensor provided in an embodiment of this application;

[0023] Figure 4 This is a schematic diagram of the circuit application of a Hall current sensor provided in an embodiment of this application;

[0024] Figure 5 This is a physical schematic diagram of a Hall current sensor provided in one embodiment of this application;

[0025] Figure 6 This is a schematic block diagram of a current sampling circuit provided in another embodiment of this application;

[0026] Figure 7This is a circuit connection diagram of an adjustment unit provided in an embodiment of this application;

[0027] Figure 8 This is a circuit connection diagram of the filtering unit, zero drift suppression unit, and signal acquisition and transmission module provided in an embodiment of this application;

[0028] Figure 9 This is an embodiment of the present application providing actual DC sampling test data and sampling curves.

[0029] In the diagram: 10. Current sampling circuit; 101. Signal acquisition and transmission module; 1011. Data conversion unit; 102. Signal conversion module; 103. Signal processing module; 1031. Adjustment unit; 1032. Filtering unit; 1033. Zero drift suppression unit. Detailed Implementation

[0030] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0031] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0032] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [the described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [the described condition or event] is detected," or "in response to detection of [the described condition or event]."

[0033] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0034] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0035] Currently, DC current acquisition often employs a shunt converter paired with a voltage and current monitor chip. This approach detects the voltage difference across the shunt, converts it into current using Ohm's law, and transmits the data to the voltage and current monitor chip for processing. While this method can achieve current acquisition when applied to DC sampling in distribution network automation terminal equipment, it suffers from the drawback of non-isolated circuitry. During electromagnetic compatibility testing, the voltage and current monitor chip may be damaged.

[0036] To address the aforementioned issues, the current sampling circuit provided in this application includes a signal acquisition and transmission module, multiple signal conversion modules, and multiple signal processing modules. Each signal conversion module corresponds one-to-one with a multiple transmission line, and each module is connected in series with its corresponding transmission line to achieve real-time monitoring of the first current signal on the transmission line. Simultaneously, each signal conversion module is electrically connected to its corresponding signal processing module, and can output a first voltage signal to the signal processing module based on the first current signal on the transmission line, thereby converting the first current signal on the transmission line. Then, the signal processing module outputs a second voltage signal based on the first voltage signal, and the signal acquisition and transmission module outputs a target signal based on the second voltage signal. Therefore, the signal conversion module in this application employs an electrical isolation design, electrically isolating the acquisition of the first current signal from the output of the first voltage signal on the transmission line, greatly improving the electromagnetic compatibility performance of the current sampling circuit. Even if the signal conversion module malfunctions, it will not affect the normal switching operation of subsequent circuits controlled by the distribution network equipment, thus effectively improving the reliability of the power supply to the distribution network equipment.

[0037] To illustrate the technical solution described in this application, specific embodiments are provided below.

[0038] Figure 1 A schematic block diagram of a current sampling circuit 10 according to an embodiment of this application is shown. See also Figure 1As shown, the current sampling circuit 10 includes a signal acquisition and transmission module 101, multiple signal conversion modules 102, and multiple signal processing modules 103. Each signal conversion module 102 corresponds one-to-one with a multiple transmission line, and each signal conversion module 102 is connected in series with its corresponding transmission line. Each signal conversion module 102 is also electrically connected to its corresponding signal processing module 103, and all signal processing modules 103 are electrically connected to the signal acquisition and transmission module 101. The signal conversion module 102 outputs a first voltage signal to the signal processing module 103 based on a first current signal from the transmission line. The signal processing module 103 outputs a second voltage signal to the signal acquisition and transmission module 101 based on the first voltage signal. The signal acquisition and transmission module 101 outputs a target signal based on the second voltage signal.

[0039] Specifically, the multiple transmission lines can include three transmission lines: closing, opening, and energy storage circuit. The closing transmission line includes manual closing / SH, closing pressure plate, closing output / HZ+, closing+ / HZ+, auxiliary contact_normally closed, closing coil / HQ, closing- / HZ-, closing output / HZ-, etc. The opening transmission line includes manual opening / SF, opening pressure plate, opening output / FZ+, opening+ / FZ+, auxiliary contact_normally open, trip coil / TQ, opening- / FZ-, opening output / FZ-, etc. The energy storage circuit transmission line includes energy storage output / CN+, energy storage+ / CN+, energy storage motor M, energy storage- / CN-, energy storage output / CN-, etc. Furthermore, Figure 1 The device also includes components such as a remote closing / protective closing / YH connected to the common terminal of the closing pressure plate and the manual closing / SH, a remote opening / protective opening / YF connected to the common terminal of the opening pressure plate and the manual opening / SF, and a power supply. The connections and working principles between these components are existing technologies and will not be elaborated upon here. Among them, the closing + / HZ+, auxiliary contact_normally closed, closing coil / HQ, closing - / HZ-, opening + / FZ+, auxiliary contact_normally open, tripping coil / TQ, opening - / FZ-, energy storage + / CN+, energy storage motor M, and energy storage - / CN- together constitute the primary equipment's switch / circuit breaker, while the other components together constitute the FTU (Feeder Terminal Unit, distribution automation feeder terminal).

[0040] In practical applications, the signal conversion module 102 can be connected in series on three transmission lines: closing, opening, and energy storage circuit. The signal conversion module 102 connected in series on the closing transmission line can detect the first current signal on the closing transmission line, convert the first current signal into a first voltage signal, and transmit the first voltage signal to the signal processing module 103 corresponding to that signal conversion module 102. Similarly, the signal conversion module 102 connected in series on the opening transmission line can detect the first current signal on the opening transmission line, convert the first current signal into a first voltage signal, and transmit the first voltage signal to the signal processing module 103 corresponding to that signal conversion module 102. Likewise, the signal conversion module 102 connected in series on the energy storage circuit transmission line can detect the first current signal on the energy storage circuit transmission line, convert the first current signal into a first voltage signal, and transmit the first voltage signal to the signal processing module 103 corresponding to that signal conversion module 102. The signal conversion module 102 in this application employs an electrical isolation design, electrically isolating the acquisition of the first current signal from the output of the first voltage signal on the transmission line, greatly improving the electromagnetic compatibility performance of the current sampling circuit 10. Even if the signal conversion module 102 fails or malfunctions, it will not affect the normal switching operation of the subsequent circuits of the distribution network equipment, thereby effectively improving the reliability of the power supply of the distribution network equipment.

[0041] It should be noted that, as Figure 1 As shown, the three signal conversion modules 102 connected in series in the closing, opening, and energy storage circuits are designated as the first signal conversion module 102, the second signal conversion module 102, and the third signal conversion module 102. Specifically, the first terminal of the first signal conversion module 102 is connected to the closing pressure plate, and the second terminal is connected to the closing output / HZ+. The first terminal of the second signal conversion module 102 is connected to the opening pressure plate, and the second terminal is connected to the opening output / FZ+. The first terminal of the third signal conversion module 102 is connected to the operating power supply, and the second terminal is connected to the energy storage output / CN+.

[0042] It should be noted that the target signal can characterize the opening and closing current and the energy storage current. The signal acquisition and transmission module 101 can transmit the target signal to the cloud or control center. The cloud or control center can monitor the electromagnetic coil current, opening and closing current and energy storage current of the primary equipment circuit breaker drive mechanism based on the target signal, and make judgments on some parameters or states of the components based on the monitoring results. Specifically, monitoring the electromagnetic coil current can predict whether the drive current is normal. If the current is within the rated range, it indicates that the drive mechanism is operating smoothly. This data can also be used as an indicator for predicting the lifespan of the drive mechanism and diagnosing primary equipment faults. The opening and closing current waveform can be used to analyze the mechanical wear and lubrication of the mechanism (such as increased mechanical resistance leading to a longer current rise time, contact bounce or arcing causing abnormal current spikes). Through opening and closing current monitoring and waveform analysis, the lifespan status of the primary equipment can be determined, whether preventive maintenance is required, and the integrity of the opening and closing operation can be verified (after the opening and closing is completed, the circuit current returns to zero, and the switch status can be determined by combining the position status). Regarding the energy storage current, the spring-operated circuit breaker needs to store energy by manually or by compressing the closing spring. It can only be closed after energy storage is completed, and the opening spring will be compressed in conjunction with the closing operation. Monitoring the energy storage current can determine the working status of components such as the energy storage mechanism motor and capacitor, as well as problems such as the capacity decay of the built-in battery in the power distribution terminal and abnormal charging modules. It can also determine mechanical conditions such as motor bearing wear, gear jamming, and spring aging by the magnitude of current fluctuations and the length of energy storage time.

[0043] It should be noted that, regarding the issue of non-isolated circuits in the background technology, existing solutions typically employ isolation chips. However, this approach not only requires additional front-end protection but also directly affects the normal switching operation of subsequent circuits should the chip fail. In contrast, all signal conversion modules 102 provided in this application can be mounted on a circuit board, meaning they are soldered onto the board. This design eliminates the need for additional front-end protection, simplifying the circuit structure and significantly reducing the design cost of the current sampling circuit 10.

[0044] In one embodiment of this application, such as Figure 2 , Figure 3 or Figure 4As shown, the signal conversion module 102 includes a Hall current sensor. The first output pin (first pin) and the second output pin (second pin) of the Hall current sensor are both electrically connected to the corresponding signal processing module 103. The first output pin (first pin) of the Hall current sensor is used to output a first voltage signal Vout, and the second output pin (second pin) of the Hall current sensor is used to output a reference voltage Vref. The third pin of the Hall current sensor is grounded, and the fourth pin of the Hall current sensor is used to be electrically connected to a first power supply. The first current detection pin (fifth pin) and the second current detection pin (sixth pin) of the Hall current sensor are both connected in series on the corresponding transmission line.

[0045] Specifically, all Hall current sensors are soldered onto the circuit board (for example, all Hall current sensors can be soldered onto the same circuit board, which reduces the risk of electromagnetic interference and signal attenuation). This is an onboard design of the Hall current sensors, and the first and second current detection pins of the Hall current sensors are electrically isolated from the other four pins. Therefore, when EMC (Electromagnetic Compatibility) interference is applied to the closing, opening, and energy storage circuits, no additional protection is needed in the current acquisition circuit (transmission line). Even if the DC current acquisition circuit fails, it will not affect the primary switching action, thereby increasing the stability and reliability of the system power supply.

[0046] It should be noted that, regarding the issue of non-isolation in the background technology, existing solutions can also use through-hole Hall current sensors (e.g., current transformers). However, through-hole Hall current sensors are relatively large, and the through-hole lead-wire process increases the cost of the terminal structure and assembly. This application, however, uses a miniature Hall current sensor with onboard PCB (Printed Circuit Board) design and PCB traces. Compared to through-hole Hall current sensors, the three acquisition loops occupy significantly less design space. Furthermore, the Hall current sensor in this application is directly soldered in a reflow oven, reducing manual wiring processes, lowering costs, and improving processing efficiency, manufacturability, and reliability. In addition, both the first and second current detection pins of the Hall current sensor use large-size copper-plated tin leads connected in series in the acquisition loop, resulting in extremely low on-resistance Rds. Moreover, after being connected in series in the opening / closing and energy storage loops, it has virtually no impact on the primary switching action.

[0047] It should be noted that the first output pin of the Hall current sensor serves as the output terminal of the signal conversion module 102, and the output first voltage signal Vout is a linear voltage signal with a fixed gain that is the same as the first current signal in the acquisition circuit.

[0048] For example, such as Figure 3 or Figure 4 As shown, a 100nF capacitor is provided between the fourth and third pins, and between the second and third pins, of the Hall current sensor to filter out high-frequency components and ensure a stable and reliable signal. The Hall current sensor model STK-20HD / K can be selected. Figure 5 As shown, the Hall current sensor of this application has a length of 19mm and a width of 11.5mm. It integrates a chip and has a significantly smaller size compared to the through-hole Hall current sensor, making it easier to assemble.

[0049] In one embodiment of this application, such as Figure 6 As shown, the signal processing module 103 includes an adjustment unit 1031, a filtering unit 1032, and a zero drift suppression unit 1033. The adjustment unit 1031, the filtering unit 1032, and the zero drift suppression unit 1033 are electrically connected in sequence. The adjustment unit 1031 is electrically connected to the corresponding signal conversion module 102, and the zero drift suppression unit 1033 is electrically connected to the signal acquisition and transmission module 101.

[0050] Specifically, the adjustment unit 1031 can receive the first voltage signal Vout, amplify or attenuate it, perform amplitude modulation, and output a first output signal to the filtering unit 1032. The filtering unit 1032 can filter out high-frequency signals in the first output signal, ensuring a smoother output second voltage signal. The zero-drift suppression unit 1033 can limit the zero-point drift of the second voltage signal within a preset range, that is, eliminate or limit the drift of the second voltage signal near zero, ensuring stable output when there is no input signal.

[0051] It should be noted that after the first output pin of the Hall current sensor outputs the first voltage signal Vout, it is usually directly transmitted to the signal acquisition and transmission module 101. However, this method introduces a large DC bias, and due to limitations such as the output impedance, gain, and dynamic range of the Hall current sensor itself, it is difficult to match suitable parameters to meet the product design requirements. Therefore, this application adds a signal processing module 103 to perform amplitude modulation, filtering, and zero drift suppression on the first voltage signal Vout before transmitting it to the signal acquisition and transmission module 101, thereby improving the accuracy of current signal acquisition.

[0052] It should be noted that, since this application includes three transmission lines for closing, opening, and energy storage circuits, three signal processing modules 103 are required. Specifically, three adjustment units 1031, three filtering units 1032, and three zero-drift suppression units 1033 are needed. The circuit structure and basic principle of each adjustment unit 1031 are identical. Therefore, in this application, only the specific circuit and basic principle of the signal processing module 103 connected to the signal conversion module 102 connected in series on the closing transmission line will be described below. The specific circuit and basic working principle of the signal processing module 103 connected to the signal conversion module 102 connected in series on other transmission lines (opening and energy storage circuits) will not be elaborated upon here.

[0053] In one embodiment of this application, such as Figure 7 As shown, the adjustment unit 1031 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first capacitor C1, a second capacitor C2, and a first operational amplifier U1. The first end of the first resistor R1 and the first end of the second resistor R2 are both electrically connected to the corresponding signal conversion module 102. The second end of the first resistor R1 is electrically connected to the first end of the third resistor R3, the first end of the second capacitor C2, and the first input terminal (inverting input terminal) of the first operational amplifier U1. The second end of the third resistor R3 is electrically connected to the second end of the second capacitor C2, the output terminal of the first operational amplifier U1, and the filter unit 1032. The first end of the fourth resistor R4 is electrically connected to the second end of the second resistor R2, the first end of the first capacitor C1, and the second input terminal (non-inverting input terminal) of the first operational amplifier U1. The second end of the fourth resistor R4 and the second end of the first capacitor C1 are both grounded.

[0054] Specifically, the first resistor R1 and the second resistor R2 both act as voltage divider resistors, preprocessing the reference voltage Vref and the first voltage signal Vout output by the Hall current sensor to provide suitable voltage signals to the two input terminals of the first operational amplifier U1. Furthermore, when the voltage transmitted to the first operational amplifier U1 is abnormal, the first resistor R1 and the second resistor R2 can limit the current flowing into the first operational amplifier U1, thereby protecting it. The third resistor R3 works in conjunction with the first resistor R1, and the fourth resistor R4 works in conjunction with the second resistor R2 to determine the voltage transmitted to the first input terminal, the voltage at the second input terminal, and the output voltage (first output signal V-out) of the first operational amplifier U1. The first capacitor C1 and the second capacitor C2 are both used for filtering to ensure the accuracy of the voltage transmitted to the second input terminal and the output voltage of the first operational amplifier U1. The first operational amplifier U1 can convert the differential signal (the signal with Vref as a reference) output by the Hall current sensor into a single-ended signal (the first output signal V-out), and amplify or attenuate the signal according to the resistor configuration to increase the signal amplitude for subsequent processing. In addition, the capacitor connected between the power supply terminal (VCC5V0) of the first op-amp U1 and ground plays a filtering and decoupling role, filtering out high-frequency noise in the power supply, making the power supply more stable, and providing a clean power supply for the first op-amp U1.

[0055] It should be noted that, since the Hall current sensor itself has a certain offset voltage, there is a DC bias of mV level when the reference voltage Vref and the output voltage (first voltage signal Vout) are not applied. A differential to single-ended circuit can be built using an operational amplifier circuit to optimize the ratio of the offset voltage to the DC sampling voltage, thereby improving the accuracy of current sampling.

[0056] For example, designers can select the resistance values ​​of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 according to the actual situation. For instance, the resistance values ​​of the first resistor R1 and the second resistor R2 can be selected as 10KΩ, and the resistance values ​​of the third resistor R3 and the fourth resistor R4 can be selected as 24KΩ.

[0057] In one embodiment of this application, such as Figure 8 As shown, the filter unit 1032 includes a fifth resistor R5 and a third capacitor C3. The first end of the fifth resistor R5 is electrically connected to the adjustment unit 1031, and the second end of the fifth resistor R5 is electrically connected to the first end of the third capacitor C3 and the zero drift suppression unit 1033, respectively. The second end of the third capacitor C3 is grounded.

[0058] Specifically, the fifth resistor R5 and the third capacitor C3 form a first-order passive low-pass filter to filter the first output signal V-out, removing high-frequency noise. By setting appropriate resistor and capacitor values, the cutoff frequency is determined, allowing effective low-frequency signals to pass smoothly while suppressing high-frequency interference signals, ultimately outputting the second voltage signal V. -HZ .

[0059] For example, designers can select the resistance value of the fifth resistor R5 and the capacitance value of the third capacitor C3 according to the actual situation. For example, the resistance value of the fifth resistor R5 can be selected as 1KΩ, and the capacitance value of the third capacitor C3 can be selected as 1nF.

[0060] In one embodiment of this application, such as Figure 8 As shown, the zero drift suppression unit 1033 includes a sixth resistor R6. The first end of the sixth resistor R6 is electrically connected to the filter unit 1032 and the signal acquisition and transmission module 101, respectively, and the second end of the sixth resistor R6 is grounded.

[0061] Specifically, the sixth resistor R6 serves as a resistance to ground and is used to suppress the second voltage signal V. -HZ Zero drift, the second voltage signal V -HZ The zero drift is limited to a certain range to ensure that the second voltage signal V transmitted to the signal acquisition and transmission module 101 is kept within a certain range. -HZ The reliability of the signal is ensured. Simultaneously, the fifth resistor R5 and the sixth resistor R6 form a voltage divider circuit to divide the first output signal V-out to obtain the second voltage signal V. -HZ .

[0062] For example, the designer can select the resistance value of the sixth resistor R6 according to the actual situation. For example, the resistance value of the sixth resistor R6 can be selected as 4.7KΩ.

[0063] In one embodiment of this application, such as Figure 8 As shown, the signal acquisition and transmission module 101 includes a data conversion unit 1011 and a processor chip. The data conversion unit 1011 is electrically connected to the processor chip and all signal processing modules 103.

[0064] Specifically, the data conversion unit 1011 can convert the simulated second voltage signal V -HZ The signal is converted into a digital signal and transmitted to the processor chip. Due to the offset voltage of the hardware circuit components, the input signal (second voltage signal V) of the data conversion unit 1011 is affected. -HZWhen no current is applied to the DC acquisition channel, there will be a very small DC bias component. The processor chip can be zeroed using software, and then the current value can be obtained by calculating the conversion factor according to the hardware design gain. Due to device differences, the rated current is injected into the circuit, and the current value is calibrated again using software. Finally, the current is applied, and the actual current values ​​of the closing, opening, and energy storage circuits can be accurately acquired, and the waveform can be recorded and transmitted to the target signal.

[0065] In one embodiment of this application, such as Figure 8 As shown, the data conversion unit 1011 includes a seventh resistor R7, an eighth resistor R8, a fourth capacitor C4, and an analog-to-digital converter (ADC). The first end of the seventh resistor R7 is electrically connected to all signal processing modules 103. The second end of the seventh resistor R7 is electrically connected to the first end of the fourth capacitor C4 and the first input terminal of the ADC. The first end of the eighth resistor R8 is grounded. The second end of the eighth resistor R8 is electrically connected to the second end of the fourth capacitor C4 and the second input terminal of the ADC. The output terminal of the ADC is electrically connected to the processor chip.

[0066] Specifically, the seventh resistor R7, the eighth resistor R8, and the fourth capacitor C4 together form a differential RC low-pass filter to achieve anti-aliasing filtering, suppress high-frequency noise, limit sampling surge current, and provide isolation and buffering to protect the analog-to-digital converter (ADC).

[0067] It should be noted that the analog-to-digital converter (ADC) communicates with the processor chip via SPI (Serial Peripheral Interface) to achieve data transmission and control signal exchange. Specifically, SPICS is the chip select signal, SPICLK is the clock signal, SPIMISO is the master input / slave output signal, and SPIMOSI is the master output / slave input signal.

[0068] For example, designers can select the resistance values ​​of the seventh resistor R7 and the eighth resistor R8, and the capacitance of the fourth capacitor C4 according to the actual situation. For instance, the resistance values ​​of both the seventh resistor R7 and the eighth resistor R8 can be selected as 1KΩ, and the capacitance of the fourth capacitor C4 can be selected as 1nF. The model of the analog-to-digital converter (ADC) can be selected as AD7616.

[0069] It should be noted that the power frequency acquisition of the distribution automation feeder terminal can share a single chip, occupying only three current sampling channels.

[0070] During the operation of the current sampling circuit 10, the relationship between the input and output signals directly determines the accuracy and effectiveness of signal processing. The following section combines... Figure 4 , Figure 7 and Figure 8The circuit diagram of the current sampling circuit 10 shown will be explained in detail with relevant formulas to illustrate the mathematical relationship and conversion mechanism between them, so as to help understand the working principle of the current sampling circuit 10.

[0071] If an STK-20HD / K type Hall current sensor with a gain of 40mV / A is selected, the first current signal I... -HZ It can be calculated using formula (1_1):

[0072]

[0073] It is important to note that the Hall current sensor gain is 40mV / A, which is equivalent to 0.04V / A.

[0074] The adjustment unit 1031 uses a differential amplifier circuit to achieve differential-to-single-ended conversion and amplitude modulation. According to the "virtual open" principle of the op-amp, the input voltage V+ at the second input terminal of the first op-amp U1 is calculated by formula (1_2); the input voltage V- at the first input terminal of the first op-amp U1 is calculated by formula (1_3).

[0075]

[0076]

[0077] According to the "virtual short" principle of the op-amp, the first output signal V-out is calculated by formula (1_4).

[0078]

[0079] With values ​​R1 = R2 and R3 = R4, formula (1_4) simplifies to (1-5):

[0080]

[0081] It should be noted that the offset voltage of the current sensor can be eliminated or compensated by adjusting the resistance values ​​of R1, R2, R3, and R4 based on formula (1_4) through the positive and negative power supplies of the first op-amp U1 and fine-tuning the resistance values ​​of R1, R2, R3, and R4. Alternatively, the offset voltage can be compensated by selecting the first op-amp U1 with offset and zero-adjustment functions.

[0082] R5 and C3 form a first-order passive low-pass filter, and the cutoff frequency fc is obtained by formula (1_6).

[0083]

[0084] Where fc is the cutoff frequency of the low-pass filter, the filter design can be completed by selecting appropriate values ​​of R5 and C3.

[0085] R6's resistance to ground suppresses zero drift, while V is obtained through the voltage divider between R5 and R6. -HZV is obtained through formula (1_7) -HZ .

[0086]

[0087] Formula (1_8) is derived by combining formulas (1_1), (1_5), and (1_7):

[0088]

[0089] Among them, V -HZ This is the voltage value obtained from the actual test of the ADC. According to formula (1_8), the processor chip can calculate I. -HZ Current value. When no current is applied to the closing circuit, the ADC will acquire a DC bias voltage in the mV or μV range, which is then zeroed via software. When the rated current is applied again, the fine-tuning coefficient is calibrated via software, thus completing the current acquisition and waveform recording.

[0090] For example, the current acquisition range is designed to be 0-30A, and the ADC measurement range is 2.5V; R1 and R2 are 10kΩ, R3 and R4 are 24kΩ, R5 is 1kΩ, and R6 is 4.7kΩ. Substituting into formula (1_8), we get formula (1_9):

[0091]

[0092] When I -HZ When the maximum design current is 30A, V -HZ It is 2.37V, which meets the design range of the ADC.

[0093] like Figure 9 As shown, the I_FZ channel represents the opening channel, the I_HZ channel represents the closing channel, and the I_CN channel represents the energy storage circuit channel. On the closing transmission line, the actual DC current sampling test data matches the theoretical calculation of formula (1_9), that is, the actual DC current sampling test data of I_FZ... -HZ With V -HZ The value satisfies the theoretical calculation value of formula (1_9). In addition, the actual DC current sampling test I on the circuit breaker and energy storage circuit transmission line is also included. -HZ With V -HZ The value also satisfies the theoretical calculation value of formula (1_9).

[0094] This application also discloses a current sampling device, including the aforementioned current sampling circuit 10. The current sampling device using the aforementioned current sampling circuit 10 can achieve high-precision acquisition and voltage conversion of transmission line current signals, effectively improving electromagnetic compatibility performance. This current sampling device, with the help of the PCB board design of the miniature Hall current sensor, significantly reduces the size and assembly cost, and reduces manual operation through automated welding process, significantly improving processing efficiency and reliability. It is suitable for scenarios such as distribution network automation terminals that have high requirements for current monitoring accuracy, reliability and space layout.

[0095] This application also discloses a power distribution automation system, including the aforementioned current sampling device and primary equipment, which are electrically connected. The power distribution automation system can improve the reliability of the primary equipment (such as circuit breakers or disconnectors) by using the current sampling device to monitor key current parameters (such as opening and closing currents, energy storage currents, and electromagnetic coil currents) in real time and accurately.

[0096] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A current sampling circuit, characterized by, The signal acquisition and uploading module, a plurality of signal conversion modules and a plurality of signal processing modules are included, a plurality of the signal conversion modules correspond to a plurality of transmission lines one by one, each of the signal conversion modules is connected in series on the corresponding transmission line, a plurality of the signal conversion modules correspond to a plurality of the signal processing modules one by one, each of the signal conversion modules is electrically connected to the corresponding signal processing module, and all the signal processing modules are electrically connected to the signal acquisition and uploading module; The signal conversion module is used for outputting a first voltage signal to the signal processing module according to a first current signal on the transmission line, the signal processing module is used for outputting a second voltage signal to the signal acquisition and uploading module according to the first voltage signal, and the signal acquisition and uploading module is used for outputting a target signal according to the second voltage signal.

2. The current sampling circuit of claim 1, wherein, The signal conversion module includes a Hall current sensor, a first output pin of the Hall current sensor and a second output pin of the Hall current sensor are electrically connected to the corresponding signal processing module, the first output pin of the Hall current sensor is used for outputting the first voltage signal, the second output pin of the Hall current sensor is used for outputting a reference voltage, and a first current detection pin of the Hall current sensor and a second current detection pin of the Hall current sensor are connected in series on the corresponding transmission line.

3. The current sampling circuit of claim 1, wherein, The signal processing module includes an adjusting unit, a filtering unit and a zero drift suppression unit, the adjusting unit, the filtering unit and the zero drift suppression unit are electrically connected in sequence, the adjusting unit is electrically connected to the corresponding signal conversion module, and the zero drift suppression unit is electrically connected to the signal acquisition and uploading module. The adjusting unit is used for outputting a first output signal to the filtering unit according to the first voltage signal, the filtering unit is used for filtering high-frequency signals in the first output signal and outputting the second voltage signal, and the zero drift suppression unit is used for limiting zero-point drift of the second voltage signal within a preset range.

4. The current sampling circuit of claim 3, wherein, The adjusting unit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first capacitor, a second capacitor and a first operational amplifier, a first end of the first resistor and a first end of the second resistor are electrically connected to the corresponding signal conversion module, a second end of the first resistor is electrically connected to a first end of the third resistor, a first end of the second capacitor and a first input end of the first operational amplifier respectively, a second end of the third resistor is electrically connected to a second end of the second capacitor, an output end of the first operational amplifier and the filtering unit respectively, a first end of the fourth resistor is electrically connected to a second end of the second resistor, a first end of the first capacitor and a second input end of the first operational amplifier respectively, and a second end of the fourth resistor and a second end of the first capacitor are grounded.

5. The current sampling circuit of claim 3, wherein, The filtering unit includes a fifth resistor and a third capacitor, a first end of the fifth resistor is electrically connected to the adjusting unit, a second end of the fifth resistor is electrically connected to a first end of the third capacitor and the zero drift suppression unit respectively, and a second end of the third capacitor is grounded.

6. The current sampling circuit of claim 3, wherein, The zero drift inhibiting unit comprises a sixth resistor, a first end of the sixth resistor is electrically connected with the filter unit and the signal acquisition and sending module respectively, and a second end of the sixth resistor is grounded.

7. The current sampling circuit of claim 1, wherein, The signal acquisition and sending module comprises a data conversion unit and a processor chip, the data conversion unit is electrically connected with the processor chip and all the signal processing modules respectively. The data conversion unit is used for outputting a conversion signal to the processor chip according to the second voltage signal, and the processor chip is used for outputting the target signal according to the conversion signal.

8. The current sampling circuit of claim 7, wherein, The data conversion unit comprises a seventh resistor, an eighth resistor, a fourth capacitor and an analog-digital converter, a first end of the seventh resistor is electrically connected with all the signal processing modules respectively, a second end of the seventh resistor is electrically connected with a first end of the fourth capacitor and a first input end of the analog-digital converter respectively, a first end of the eighth resistor is grounded, a second end of the eighth resistor is electrically connected with a second end of the fourth capacitor and a second input end of the analog-digital converter respectively, and an output end of the analog-digital converter is electrically connected with the processor chip.

9. A current sampling device, characterized by The current sampling circuit comprises the current sampling circuit according to any one of claims 1-8.

10. A power distribution automation system, characterized by, The current sampling device comprises a primary device and the current sampling device according to claim 9, and the primary device and the current sampling device are electrically connected.

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