Open-close type direct current leakage current detection device based on TMR

Abstract

The invention belongs to the technical field of direct current monitoring, and discloses a TMR-based open-close type direct current leakage current detection device, which comprises a magnetic core, one or more pairs of TMR sensors, a secondary side feedback coil and a main control circuit, and is characterized in that the magnetic core is provided with air gaps which are oppositely arranged; the TMR sensors are symmetrically arranged in the air gap; the secondary side feedback coil is wound on the surface of the magnetic core and forms closed-loop control with the main control circuit; the main control circuit comprises an acquisition feedback circuit, a secondary side detection circuit and a main control chip, the acquisition feedback circuit acquires signals of the TMR sensor under the control of the main control chip, generates feedback current and inputs the feedback current to the secondary side feedback coil, and the secondary side detection circuit is connected between the secondary side feedback coil and the main control chip. And the main control chip collects the secondary side voltage of the secondary side detection circuit and calculates to obtain the direct current leakage current. According to the invention, direct current leakage current detection with high sensitivity, low drift and strong anti-interference capability is realized under the open-close structure, and the requirements of a modern electric power system on continuity, safety and maintainability are met.

Description

Technical Field

[0001] The present invention relates to DC current monitoring technology in power systems, specifically to an open-close DC leakage current detection device based on tunnel magnetoresistance (TMR) technology. The device is suitable for leakage current detection and insulation monitoring in DC power supply systems such as power grids, data centers, rail transit, and new energy. Background Art

[0002] In modern power systems, the use of DC power supply continues to expand, encompassing power substations, data centers, photovoltaic energy storage systems, and rail transit. Because DC systems lack a natural zero point, insulation failures can cause persistent leakage or even accidents. Therefore, high-precision leakage current detection has become a core method for ensuring system safety. The insulation state of a DC system is crucial to its safe operation, and DC leakage current detection is a key method for assessing insulation performance. Currently, mainstream DC leakage current sensor solutions on the market primarily include closed-type and open-type structures.

[0003] Closed-type sensors have a compact structure, but they usually require power outages during on-site installation and maintenance, which is not conducive to continuous system operation. The open-type structure supports installation and maintenance without power outages, has better operability, and is particularly suitable for power grid transformation and data center power outage detection scenarios. As power operation and maintenance have increasingly stringent requirements for "uninterrupted maintenance" capabilities, traditional closed-type current sensors require power outages during installation and replacement, which easily bring operational risks and system interruptions, and are no longer able to meet actual usage needs. The open-type current sensor, due to its ability to be quickly installed, disassembled, and replaced while the system is energized, has become the preferred structure for operation and maintenance-friendly products and is widely used in high-reliability scenarios such as transformation projects, on-site maintenance, and power grid power outage detection.

[0004] The mainstream open-and-close DC leakage current sensors currently on the market basically use fluxgate technology. Although fluxgate sensors have high accuracy in closed magnetic circuits, the presence of air gaps in the open-and-close structure makes it difficult for the magnetic core to saturate, resulting in decreased sensitivity, unstable zero point, and severe temperature drift. It is difficult to guarantee the accuracy of small current detection and cannot meet the requirements of high-precision scenarios such as DC insulation detection. At the same time, the fluxgate technology solution is highly dependent on the core material and structural process, resulting in complex structure, high cost, difficult debugging, and difficulty in achieving modularization, generalization, and high reliability. Therefore, the market urgently needs a new detection solution that can achieve high-sensitivity, low-drift, and strong anti-interference capability of DC leakage current detection in an open-close structure to meet the requirements of modern power systems for continuity, safety, and maintainability. Summary of the Invention

[0005] The purpose of the present invention is to provide a TMR-based open-close DC leakage current detection device, which can achieve high sensitivity, low drift, and strong anti-interference ability of DC leakage current detection in an open-close structure, meeting the requirements of modern power systems for continuity, safety and maintainability.

[0006] To achieve the above object, the technical solution adopted by the present invention is: A TMR-based open-close DC leakage current detection device includes a magnetic core, one or more pairs of TMR sensors, a secondary feedback coil, and a main control circuit, wherein: The magnetic core is provided with air gaps arranged opposite to each other; The TMR sensor is symmetrically placed in the air gap of the magnetic core; The secondary feedback coil is wound on the surface of the magnetic core and forms a closed-loop control with the main control circuit; The main control circuit includes an acquisition feedback circuit, a secondary side detection circuit and a main control chip. The acquisition feedback circuit acquires the signal of the TMR sensor under the control of the main control chip and generates a feedback current that is input to the secondary side feedback coil. The secondary side detection circuit is connected between the secondary side feedback coil and the main control chip. The main chip acquires the secondary side voltage of the secondary side detection circuit and calculates the DC leakage current.

[0007] Several optional methods are also provided below, but they are not intended to be additional limitations on the above-mentioned overall solution. They are merely further supplements or optimizations. Under the premise that there are no technical or logical contradictions, each optional method can be combined separately for the above-mentioned overall solution, or multiple optional methods can be combined.

[0008] Preferably, the acquisition feedback circuit includes a chopping modulation circuit, a signal amplification circuit, a power amplification circuit and a feedback circuit, wherein: The chopping modulation circuit is connected to the output end of the TMR sensor and performs chopping modulation on the output of the TMR sensor under the control of the main control chip; The signal amplifying circuit is connected between the output end of the TMR sensor and the input end of the power amplifying circuit, and is used to amplify the output signal of the TMR sensor; The power amplifier circuit is connected between the signal amplifier circuit and the feedback circuit, and is used to amplify the power of the output of the signal amplifier circuit; The feedback circuit is connected between the power amplifier circuit and the secondary feedback coil, and is used for collecting the feedback current of the power amplifier circuit and inputting it into the secondary feedback coil.

[0009] Preferably, the acquisition feedback circuit further includes a temperature compensation circuit and a zero drift compensation circuit, wherein: The temperature compensation circuit is connected to the reference voltage terminal of the TMR sensor and is used to perform temperature compensation on the output of the TMR sensor; The zero drift compensation circuit is connected to the signal amplification circuit and is used to perform zero drift compensation on the signal amplification circuit under the control of the main control chip.

[0010] Preferably, the secondary side detection circuit includes a sampling resistor, a hardware demodulation circuit and a filter circuit, wherein: One end of the sampling resistor is connected to the output end of the secondary feedback coil, and the other end is grounded; The hardware demodulation circuit is connected between the output end of the secondary feedback coil and the filter circuit, and is used to demodulate the voltage signal; The filtering circuit is connected between the hardware demodulation circuit and the main control chip, and is used for filtering the voltage signal demodulated by the hardware demodulation circuit and then transmitting it to the main control chip.

[0011] Preferably, the main control chip collects the secondary side voltage of the secondary side detection circuit and calculates the DC leakage current, and performs the following operations: Digitally filter the collected secondary voltage; The zero-state calibration model is used to perform data correction on the secondary voltage after digital filtering. Perform data compensation on the secondary side voltage after data correction according to the temperature drift coefficient and time drift coefficient; Using a detection algorithm to detect the secondary side voltage after data compensation, and outputting a detection result, wherein the detection result is the presence or absence of a DC leakage current; If the detection result shows that there is no DC leakage current, the zero point voltage is adjusted according to the secondary voltage; otherwise, the DC leakage current is calculated according to the secondary voltage.

[0012] Preferably, the calibration process of the zero-state calibration model is as follows: In the absence of DC leakage current, the actual voltage output by the TMR sensor is collected; Data fitting is performed based on the ideal zero-point output voltage and actual voltage of the TMR sensor to obtain a zero-state calibration model of the actual voltage with respect to the ideal zero-point output voltage.

[0013] Preferably, the data compensation is performed on the secondary voltage after data correction according to the temperature drift coefficient and the time drift coefficient, and the following operations are performed: Where, is the secondary side voltage after data compensation, is the secondary side voltage after data correction, is the sensitivity drift coefficient, is the supply voltage of the TMR sensor, is the zero drift of the TMR sensor in the initial state, is the zero drift coefficient, is the sensitivity temperature drift coefficient, is the temperature change relative to the initial state of the TMR sensor, is the sensitivity time drift coefficient, is the time change relative to the initial state of the TMR sensor, is the zero point temperature drift coefficient, is the zero point time drift coefficient.

[0014] Preferably, the detection algorithm is a time domain threshold detection algorithm, and the execution process of the time domain threshold detection algorithm is as follows: The difference between the secondary voltage after data compensation and the zero-point voltage of the TMR sensor is calculated as the actual voltage difference. If the actual voltage difference is greater than the first abnormal threshold, it indicates that a DC leakage current exists; otherwise, no DC leakage current exists.

[0015] Preferably, the detection algorithm is a frequency domain effective value detection algorithm, and the execution process of the frequency domain effective value detection algorithm is as follows: The secondary voltage after data compensation is converted to the frequency domain, and the effective value at 0 Hz in the frequency domain is taken as the actual voltage value. If the difference between the actual voltage value and the zero-point voltage is greater than the second abnormal threshold, it indicates that DC leakage current exists; otherwise, no DC leakage current exists.

[0016] The TMR-based open-and-close DC leakage current detection device provided by the present invention realizes high-precision (±1%) DC leakage current monitoring in low current scenarios (±10mA) while ensuring the maintainability of the open-and-close structure. In addition, the present invention supports rapid installation, replacement and on-site debugging, meeting the requirements of uninterrupted maintenance; has low long-term zero-point offset and long-term operational stability; has strong anti-interference ability and is suitable for complex electromagnetic environments; is easy to integrate and adapts to scenarios such as data centers, DC panels, and power grid branches; meets the requirements of uninterrupted detection and rapid maintenance, and has significant promotion value in scenarios such as data centers, power grids, rail transit, and new energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the TMR-based open-close DC leakage current detection device of the present invention; Figure 2 Schematic diagram of the installation of the TMR sensor of the present invention on the magnetic core; Figure 3 Schematic diagram of the structure of the main control circuit of the present invention; Figure 4 This is a flow chart of leakage current detection performed by the main control chip of the present invention; Figure 5 Schematic diagram of the experimental device of the present invention. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0020] The present invention provides an open-and-close DC leakage current detection device based on TMR. By utilizing the high sensitivity of TMR elements to changes in weak magnetic fields, combined with a closed-loop magnetic compensation structure, an adaptive zero-point adjustment algorithm, and a modular structural design, the device achieves leakage current detection with high precision, low power consumption, and strong anti-interference capability without powering off.

[0021] like Figure 1 As shown, the TMR-based split-type DC leakage current detection device of this embodiment includes a magnetic core, one or more pairs of TMR sensors, a secondary feedback coil and a main control circuit.

[0022] (1) Magnetic core: like Figure 2 As shown, this embodiment utilizes a ring-shaped or square magnetic core made of highly permeable material with an openable and closable structure. The core features relatively spaced air gaps, controlled to a range of 1.5 to 4.5 mm, for the placement of magnetic sensitive units. The core is connected via a metal hinge and features a mortise-and-tenon joint to ensure air gap alignment after each opening and closing, maintaining magnetic circuit consistency. The core is encased in an insulating plastic shell and secured with snaps or screws.

[0023] In addition, this embodiment uses a hinge + mortise and tenon structure to ensure stable repeatable positioning of the magnetic core air gap (controlled within 3.0~3.5mm), and the replaceable aperture module supports conductors of different specifications; the shell material complies with the UL94-V0 flame retardant standard and is suitable for DIN rail / panel installation, facilitating rapid on-site deployment and replacement.

[0024] The inner diameter of the core through-hole can accommodate conductors of varying diameters (e.g., 20-80mm). The device can be quickly installed using DIN rail clips or panel screws without powering off, meeting the integration requirements of various electrical cabinets, terminal cabinets, and DC panels.

[0025] (2) TMR sensor: This embodiment utilizes single or multiple pairs of TMR sensors, symmetrically and differentially arranged on the mid-axis of the magnetic core's air gap. These sensors provide real-time sensing of magnetic field changes generated by the conductor. Symmetrical detection effectively suppresses common-mode magnetic interference, such as that caused by geomagnetic fields and external electromagnetic fields. Combined with the magnetic shielding layer within the housing, this enhances the device's anti-interference capabilities. The TMR sensors are connected to the main control circuitry using flexible connectors or FPC soldering.

[0026] A single or multiple pairs of TMR devices are arranged at the air gap of the magnetic core opening and closing structure to sense the magnetic flux change. Combined with the secondary feedback coil, a closed-loop magnetic balance circuit is constructed. The magnetic field caused by the primary leakage current is balanced by the secondary compensation current, and the primary leakage current is accurately calculated based on the ampere-turn balance formula.

[0027] (3) Secondary feedback coil: The secondary feedback coil is wound on the magnetic core with 100 turns (adjustable according to actual conditions). The secondary feedback coil and the main control circuit form a closed-loop control. The main control circuit controls the feedback current according to the output of the TMR sensor to form magnetic field compensation and realize magnetic flux balance detection. That is, the output signal of the TMR sensor is amplified and drives the secondary feedback coil to generate a reverse magnetic field to form magnetic balance. The secondary current is detected and then the primary current is calculated.

[0028] (4) Main control circuit: The main control circuit includes an acquisition feedback circuit, a secondary side detection circuit and a main control chip. The acquisition feedback circuit acquires the signal of the TMR sensor under the control of the main control chip, and generates a feedback current which is input to the secondary side feedback coil. The secondary side detection circuit is connected between the secondary side feedback coil and the main control chip. The main control chip acquires the secondary side voltage of the secondary side detection circuit and calculates the DC leakage current.

[0029] This embodiment utilizes a RISC-V architecture MCU with a built-in high-precision ADC module. Its peripherals include signal amplification circuits, power amplifier circuits, sampling resistors, chopper modulation circuits, zero-drift compensation circuits, temperature drift compensation circuits, RS485 communication circuits, and external (protection) interfaces. The MCU performs digital filtering, magnetic field calculation, calibration compensation, and data communication based on the TMR signal. The chopper modulation module, located at the front end of the TMR sensor, eliminates the 1 / f noise of the TMR device and recovers the valid signal through software / hardware demodulation. The downstream circuitry consists of a high-gain amplifier, sampling ADC, and MCU, equipped with a feedback current drive channel, forming a closed-loop system.

[0030] (4-1) Collection feedback circuit: like Figure 3As shown in the figure (for intuitive display, one TMR represents one or more pairs of TMR sensors), the acquisition feedback circuit of this embodiment includes a chopping modulation circuit, a signal amplification circuit, a power amplification circuit and a feedback circuit, wherein: The chopping modulation circuit is connected to the output end of the TMR sensor and performs chopping modulation on the output of the TMR sensor under the control of the main control chip (the main control chip sends a PWM signal).

[0031] The signal amplifier circuit is connected between the output of the TMR sensor and the input of the power amplifier circuit to amplify the TMR sensor output. It's easy to understand that the TMR sensor outputs a differential signal. The differential positive voltages of one or more pairs of TMR sensors are connected to the positive input of the signal amplifier circuit (considered the positive total input), while the differential negative voltages of one or more pairs of TMR sensors are connected to the negative input of the signal amplifier circuit (considered the negative total input). In this case, the chopper modulation circuit acts on both the positive total input and the negative total input.

[0032] The power amplifier circuit is connected between the signal amplifier circuit and the feedback circuit, and is used for performing power amplification on the output of the signal amplifier circuit.

[0033] The feedback circuit is connected between the power amplifier circuit and the secondary feedback coil, and is used to collect the feedback current of the power amplifier circuit and input it into the secondary feedback coil.

[0034] In order to further improve the accuracy of the sampled signal, the acquisition feedback circuit of this embodiment further includes a temperature compensation circuit and a zero drift compensation circuit, wherein: The temperature compensation circuit is connected to the reference voltage terminal of the TMR sensor and is used to perform temperature compensation on the output of the TMR sensor.

[0035] The zero drift compensation circuit is connected to the signal amplifying circuit and is used to perform zero drift compensation on the signal amplifying circuit under the control of the main control chip (the main control chip is controlled by serial communication).

[0036] It should be noted that the chopper modulation circuit, signal amplification circuit, power amplification circuit, feedback circuit, temperature compensation circuit and zero drift compensation circuit in this embodiment can adopt a conventional circuit structure. Under the premise of achieving the corresponding functions, this embodiment does not limit the circuit structure.

[0037] (4-2) Secondary side detection circuit: The secondary side detection circuit of this embodiment includes a sampling resistor, a hardware demodulation circuit, and a filter circuit, wherein: One end of the sampling resistor is connected to the output end of the secondary feedback coil, and the other end is grounded.

[0038] The hardware demodulation circuit is connected between the output end of the secondary feedback coil and the filter circuit, and is used for demodulating the voltage signal.

[0039] The filter circuit is connected between the hardware demodulation circuit and the main control chip, and is used for filtering the voltage signal demodulated by the hardware demodulation circuit and then transmitting it to the main control chip.

[0040] It should be noted that the hardware demodulation circuit and filtering circuit in this embodiment can adopt a conventional circuit structure. Under the premise of achieving corresponding functions, this embodiment does not limit the circuit structure.

[0041] (4-3) Main control chip: The main control chip uses a digital potentiometer combined with an adaptive fitting model to initiate zero-adjustment commands or periodic self-tests, achieving real-time compensation for zero point, temperature drift, and time drift, ensuring long-term operational accuracy. An integrated EEPROM and Flash dual storage structure stores information such as zero point calibration, temperature drift parameters, and fault records, ensuring data is not lost during power outages and automatically restoring calibration parameters upon power-up. It also supports RS485 Modbus protocol communication, configurable addresses, and connection to application systems with up to 120 nodes, enabling centralized insulation monitoring and alarm linkage.

[0042] like Figure 4 As shown, the main control chip collects the secondary side voltage of the secondary side detection circuit and calculates the DC leakage current. The specific process is as follows: Step 1: Collect the secondary voltage through the built-in ADC module As the sensor output voltage, the collected secondary voltage is digitally filtered. , Represents digital filter functions, including IIR low-pass filtering, Kalman filtering, etc. is the secondary side voltage after digital filtering.

[0043] Step 2: Calibrate the model using zero state , perform data correction on the secondary voltage after digital filtering , is the secondary voltage after data correction. The calibration process is as follows: in the absence of DC leakage current, the actual voltage output by the TMR sensor is collected; data fitting is performed based on the ideal zero-point output voltage and the actual voltage of the TMR sensor to obtain a zero-state calibration model of the actual voltage with respect to the ideal zero-point output voltage.

[0044] This part refers to the establishment of the system zero-point state model when the leakage current of the device to be tested is 0. Assuming that the ideal zero-point output voltage is , the actual zero-point output voltage collected is .Will and The relationship is expressed as: Generally speaking, The display expression can be: , That is, zero drift. However, due to the influence of TMR sensor technology and circuit nonlinear factors on system output, there is a deviation between the model and the actual situation. Therefore, before leaving the factory, a large number of TMR sensor zero-point output voltages can be collected with the help of a stable current source to obtain The model can better reflect the characteristic differences of the TMR sensor itself under specific environment and obtain a more accurate zero point. For model fitting, you can consider using curve fitting, least squares method, neural network and other algorithms, and take the inverse function To calculate the ideal zero-point output voltage, thus achieving data correction.

[0045] Step 3: Perform data compensation on the secondary voltage after data correction according to the temperature drift coefficient and the time drift coefficient.

[0046] The working zero point and sensitivity of the TMR sensor will drift with temperature and time, that is, temperature drift and time drift will occur. Assuming the original working zero drift is ( ), the sensitivity is ( ). The zero point temperature drift coefficient is ( ), the sensitivity temperature drift coefficient is ( ), the drift coefficient at zero point is ( ), the drift coefficient is ( ),in is the time unit. If the TMR sensor power supply voltage is , at a given working magnetic field change Under this condition, the output of the TMR sensor is as follows: in, is the temperature change relative to the initial state of the TMR sensor, is the time change relative to the initial state of the TMR sensor. Once the above drift coefficient index is known, adaptive zero point correction can be performed in real time according to the current ambient temperature change, and the output data can be compensated accordingly. Specifically, the output after compensation is: Where, is the secondary side voltage after data compensation, is the secondary side voltage after data correction, is the sensitivity drift coefficient, is the zero drift coefficient.

[0047] Step 4: Use a detection algorithm to detect the secondary voltage after data compensation, and output a detection result, which is the presence or absence of DC leakage current.

[0048] The detection algorithm in this embodiment is a time domain threshold detection algorithm or a frequency domain effective value detection algorithm, wherein the execution process of the time domain threshold detection algorithm is as follows: the difference between the secondary side voltage after data compensation and the zero point voltage of the TMR sensor is calculated as the actual voltage difference. If the actual voltage difference is greater than the first abnormal threshold (the threshold is given according to the data characteristics of the time domain-voltage, and the threshold value is related to the time domain digital voltage variance), it indicates that a DC leakage current exists; otherwise, no DC leakage current exists.

[0049] The execution process of the frequency domain effective value detection algorithm is as follows: the secondary side voltage after data compensation is converted to the frequency domain, and the effective value (DC) at 0Hz in the frequency domain (i.e., the position where the frequency is 0) is taken as the actual voltage value. If the difference between the actual voltage value and the zero-point voltage is greater than the second abnormal threshold (the threshold is given according to the data characteristics of the frequency domain-voltage, and the size of the threshold is related to the frequency domain voltage variance), it indicates that DC leakage current exists; otherwise, no DC leakage current exists.

[0050] Step 5. If the test result indicates no DC leakage current, adjust the zero-point voltage based on the secondary voltage. Otherwise, calculate the DC leakage current based on the secondary voltage. DC leakage current = (current voltage - zero-point voltage) / system sensitivity. System sensitivity is related to the number of turns of the closed-loop feedback coil (theoretically, system sensitivity is a constant). If leakage current is determined to be absent, adjust the zero-point voltage to the current voltage value. If leakage current is present, do not perform zero-point adjustment.

[0051] By combining the high sensitivity of TMR with a closed-loop magnetic balance detection method, the present invention proposes a high-precision detection scheme for DC leakage current that can be used in open-and-close structures. This scheme breaks through the bottleneck that the flux gate cannot adapt to the open-and-close structure, takes into account both high precision and on-site maintenance requirements. It is suitable for leakage monitoring scenarios of DC power supply systems with high requirements for accuracy and reliability and uninterrupted operation and maintenance, and has significant engineering application value and industrialization prospects.

[0052] The present invention solves the problems of poor detection accuracy, weak anti-interference and difficult maintenance in the existing technology under the open and close structure. It has the advantages of simple structure, moderate cost and stable performance. It is particularly suitable for insulation monitoring scenarios of power DC systems with high requirements on accuracy, reliability and maintenance convenience, and has good market application prospects and technical promotion value.

[0053] like Figure 5 As shown, in order to intuitively demonstrate the advantages of the TMR-based open-close DC leakage current detection device of this application, the following is explained through experiments: Environmental conditions: Temperature ℃: 20±2; Humidity %: 65±5; Atmospheric pressure kPa: 86-106.

[0054] Experimental equipment: The accuracy of the measured leakage current can reach 0.01mA; the auxiliary power supply deviation is ±2%.

[0055] Test instructions: 1. Before the test, the leakage current is preheated for 30 minutes and then zeroed. 2. After entering the accuracy test, the zeroing operation cannot be performed. 3. During the accuracy level test, the position and direction of the sensor cannot be moved after placement. 4. Before entering the test, the sensor is operated in three full-scale ranges on the positive and negative ranges (+10mA, -10mA).

[0056] Test method: Reference standard JB 11205-2011.

[0057] Test results: High-precision (±1%) DC leakage current monitoring is achieved in low current scenarios (±10mA).

[0058] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] The above-described embodiments merely illustrate several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A TMR-based open-close DC leakage current detection device, characterized in that: The TMR-based open-close DC leakage current detection device includes a magnetic core, one or more pairs of TMR sensors, a secondary feedback coil, and a main control circuit, wherein: The magnetic core is provided with air gaps arranged opposite to each other; The TMR sensor is symmetrically placed in the air gap of the magnetic core; The secondary feedback coil is wound on the surface of the magnetic core and forms a closed-loop control with the main control circuit; The main control circuit includes an acquisition feedback circuit, a secondary side detection circuit and a main control chip. The acquisition feedback circuit acquires the signal of the TMR sensor under the control of the main control chip and generates a feedback current that is input to the secondary side feedback coil. The secondary side detection circuit is connected between the secondary side feedback coil and the main control chip. The main chip acquires the secondary side voltage of the secondary side detection circuit and calculates the DC leakage current.

2. The TMR-based open-close DC leakage current detection device according to claim 1, characterized in that: The acquisition feedback circuit includes a chopping modulation circuit, a signal amplification circuit, a power amplification circuit and a feedback circuit, wherein: The chopping modulation circuit is connected to the output end of the TMR sensor and performs chopping modulation on the output of the TMR sensor under the control of the main control chip; The signal amplifying circuit is connected between the output end of the TMR sensor and the input end of the power amplifying circuit, and is used to amplify the output signal of the TMR sensor; The power amplifier circuit is connected between the signal amplifier circuit and the feedback circuit, and is used to amplify the power of the output of the signal amplifier circuit; The feedback circuit is connected between the power amplifier circuit and the secondary feedback coil, and is used for collecting the feedback current of the power amplifier circuit and inputting it into the secondary feedback coil.

3. The TMR-based open-close DC leakage current detection device according to claim 2, characterized in that: The acquisition feedback circuit further includes a temperature compensation circuit and a zero drift compensation circuit, wherein: The temperature compensation circuit is connected to the reference voltage terminal of the TMR sensor and is used to perform temperature compensation on the output of the TMR sensor; The zero drift compensation circuit is connected to the signal amplification circuit and is used to perform zero drift compensation on the signal amplification circuit under the control of the main control chip.

4. The TMR-based open-close DC leakage current detection device according to claim 1, characterized in that: The secondary side detection circuit includes a sampling resistor, a hardware demodulation circuit and a filter circuit, wherein: One end of the sampling resistor is connected to the output end of the secondary feedback coil, and the other end is grounded; The hardware demodulation circuit is connected between the output end of the secondary feedback coil and the filter circuit, and is used to demodulate the voltage signal; The filtering circuit is connected between the hardware demodulation circuit and the main control chip, and is used for filtering the voltage signal demodulated by the hardware demodulation circuit and then transmitting it to the main control chip.

5. The TMR-based open-close DC leakage current detection device according to claim 1, characterized in that: The main control chip collects the secondary side voltage of the secondary side detection circuit and calculates the DC leakage current, and performs the following operations: Digitally filter the collected secondary voltage; The zero-state calibration model is used to perform data correction on the secondary voltage after digital filtering. Perform data compensation on the secondary side voltage after data correction according to the temperature drift coefficient and time drift coefficient; Using a detection algorithm to detect the secondary side voltage after data compensation, and outputting a detection result, wherein the detection result is the presence or absence of a DC leakage current; If the test result shows that there is no DC leakage current, the zero point voltage is adjusted according to the secondary voltage; Otherwise, the DC leakage current is calculated based on the secondary voltage.

6. The TMR-based open-close DC leakage current detection device according to claim 5, characterized in that: The calibration process of the zero-state calibration model is as follows: In the absence of DC leakage current, the actual voltage output by the TMR sensor is collected; Data fitting is performed based on the ideal zero-point output voltage and actual voltage of the TMR sensor to obtain a zero-state calibration model of the actual voltage with respect to the ideal zero-point output voltage.

7. The TMR-based open-close DC leakage current detection device according to claim 5, characterized in that: The data compensation is performed on the secondary voltage after data correction according to the temperature drift coefficient and the time drift coefficient, and the following operations are performed: Where, is the secondary side voltage after data compensation, is the secondary side voltage after data correction, is the sensitivity drift coefficient, is the supply voltage of the TMR sensor, is the zero drift of the TMR sensor in the initial state, is the zero drift coefficient, is the sensitivity temperature drift coefficient, is the temperature change relative to the initial state of the TMR sensor, is the sensitivity time drift coefficient, is the time change relative to the initial state of the TMR sensor, is the zero point temperature drift coefficient, is the zero point time drift coefficient.

8. The TMR-based open-close DC leakage current detection device according to claim 5, characterized in that: The detection algorithm is a time domain threshold detection algorithm, and the execution process of the time domain threshold detection algorithm is as follows: The difference between the secondary voltage after data compensation and the zero-point voltage of the TMR sensor is calculated as the actual voltage difference. If the actual voltage difference is greater than the first abnormal threshold, it indicates that a DC leakage current exists; otherwise, no DC leakage current exists.

9. The TMR-based open-close DC leakage current detection device according to claim 5, characterized in that: The detection algorithm is a frequency domain effective value detection algorithm, and the execution process of the frequency domain effective value detection algorithm is as follows: The secondary voltage after data compensation is converted to the frequency domain, and the effective value at 0 Hz in the frequency domain is taken as the actual voltage value. If the difference between the actual voltage value and the zero-point voltage is greater than the second abnormal threshold, it indicates that DC leakage current exists; otherwise, no DC leakage current exists.

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