Buckle type self-power-taking wireless communication current transformer

Abstract

The invention discloses a buckle type self-power-taking wireless communication current transformer which comprises a buckle type current transformer module, an induction power-taking module, a discharge control module, a sampling compensation module and a wireless communication module. The buckle type current transformer module is used for inducing current from the high-voltage power transmission line; the induction electricity taking module induces energy from a high-voltage transmission line through an electricity taking CT, outputs stable direct current after rectification, filtering and voltage stabilization processing, and supports lithium battery charging and energy storage at the same time. And the discharge control module adopts a hysteresis comparator design, so that the safe operation of a post-stage circuit is ensured. The sampling compensation module accurately samples and compensates the current signal, and transmits the data to the wireless communication module in real time. The wireless communication module takes an STM32 microcontroller and an NBIOT communication module as a core, supports low-power-consumption and long-distance data transmission, realizes efficient data exchange and fault alarm through an MQTT protocol, simplifies equipment installation, and is suitable for a real-time monitoring scene of a high-voltage transmission line.

Description

Technical Field

[0001] The invention relates to the technical field of electric power monitoring, in particular to a snap-on type self-powered wireless communication current transformer. Background Art

[0002] Current transformers are widely used in measurement and protection equipment for power systems, but traditional designs usually rely on external power supply and transmit data through wired communication. This method has power supply limitations. Traditional current transformers require external power supply, but wiring in high-voltage transmission line environments is difficult and the power supply cost is high; communication is unstable, and wired communication methods are easily interfered by complex environments, making it difficult to achieve long-distance, real-time data transmission; it lacks flexibility, and the equipment installation and maintenance are complex, making it unsuitable for use in remote areas.

[0003] With the rapid development of the Internet of Things and wireless communication technology, researchers have proposed solutions to achieve autonomous power supply through inductive power supply technology and transmit data through wireless communication technology. However, existing technologies still have problems such as unstable inductive power supply, high power consumption of communication modules, and imperfect protection mechanisms. A new type of equipment is urgently needed to overcome these challenges. Summary of the invention

[0004] The present invention designs a snap-on self-powered wireless communication current transformer, which aims to solve the power supply and communication problems of high-voltage transmission line monitoring equipment, and provides a snap-on current transformer system with compact structure, reliable operation and convenient installation, so as to realize stable acquisition of electric energy from high-voltage transmission lines and get rid of dependence on external power supply; realize long-distance and real-time data transmission through low-power wireless communication modules; and improve the safety and reliability of equipment operation through multiple protection mechanisms.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: A snap-on self-powered wireless communication current transformer, comprising: a snap-on current transformer module, an inductive power supply module, a leakage control module, a sampling compensation module and a wireless communication module; the output end of the snap-on current transformer module is respectively connected to the inductive power supply module and the sampling compensation module, the output end of the inductive power supply module is connected to the leakage control module, the output end of the leakage control module is connected to the sampling compensation module and the wireless communication module; the output end of the sampling compensation module is connected to the wireless communication module; The snap-on current transformer module is used to sense current from a high-voltage transmission line; The induction power module includes a power CT, a rectifier circuit, a filter circuit and a voltage stabilizing circuit. The power CT is used to obtain energy from the secondary side of the coil and charge the lithium battery for energy storage. The rectifier circuit is used to convert the induced AC current into DC power. The filter circuit is used to stabilize the output DC voltage. The leakage control module controls the MOS tube through a hysteresis comparator to prevent overcurrent or overvoltage from damaging subsequent circuits; The sampling and compensation module samples and compensates the current signal, and transmits the collected data to the wireless communication module in real time; The wireless communication module includes an STM32 microcontroller and an NBIOT communication module, which are used to receive the collected current data and transmit it wirelessly to a remote server.

[0006] Furthermore, the induction power module optimizes the core structure by using high magnetic permeability materials and selects the optimal number of turns according to the load matching relationship to obtain high conversion efficiency of electromagnetic energy. The expression is as follows: ; in E 2 is the secondary side induced voltage, R 2 is the load resistance; It also enables the inductive power module to stably output 12V DC voltage within the current range of 0A to 120A.

[0007] Furthermore, the equivalent circuit of the power CT and the load during rectification and filtering in the inductive power module, the rectification circuit adopts a full-bridge rectification design, composed of four diodes, to ensure that the induced AC power is converted into DC power; assuming that the secondary side output voltage is U 2 , the effective value satisfies ;in is the sinusoidal current equivalent to the secondary side from the primary side, R L is the load resistance; after rectification and filtering, the output DC voltage , 1.4V is the voltage drop of the rectifier bridge; a transient suppression diode TVS is connected to the front end of the rectifier bridge, and its transient suppression voltage is determined by the maximum induced current of the high-voltage line to protect the subsequent circuit from damage by overvoltage.

[0008] Furthermore, the rectifier circuit and the voltage stabilizing circuit both adopt a full-bridge rectifier design combined with an LC filter circuit, and the LC filter circuit is composed of an inductor. L and capacitor C The cut-off frequency is given by the formula Determine and ensure that the voltage fluctuation is less than 0.1V, eliminate high-frequency interference, and output a stable DC voltage; a linear voltage regulator is used to convert the induced AC power into a 12V stable DC voltage to power the wireless communication module and other subsequent equipment.

[0009] Specifically, it also includes the analysis of the circuit after rectification and filtering. For the voltage-stabilized output circuit, due to the influence of the rectifier bridge and the filter capacitor, the relationship between the equivalent load voltage and the excitation current waveform is as follows: Considered as a square wave, the excitation current It is a triangle, and its calculation formula is: ; in, For time; L is the magnetizing inductance, T is the AC cycle; average load current I av The calculation needs to take into account the rectifier bridge diode voltage drop of 1.4V, the formula is: ; is the effective value of the transformer secondary voltage.

[0010] Specifically, the control logic of the leakage control module is designed with a hysteresis comparator, and the hysteresis characteristic is determined by the upper and lower threshold voltages, and the expression is as follows: ;in is the upper threshold voltage; is the reference voltage; is the lower line threshold voltage; is the feedback resistor; is the voltage divider resistor.

[0011] Specifically, under the condition of pure resistance load, the relationship between the secondary side output power and the load of the transformer is: ; in is the core magnetic path length of the transformer, The power frequency is 50Hz. is the primary current measurement, N 2 is the number of turns on the secondary side, S is the core cross-sectional area, μ is the magnetic permeability; through this formula and actual simulation results, it can be known that the maximum power of the CT is proportional to the square of the primary current. Since it is optimal when the load resistance is common-mode matched, the power output is stable when the core is not saturated, so the excitation current needs to be controlled to be less than the saturation current.

[0012] Furthermore, the control core of the wireless communication module is based on the STM32 microcontroller, which controls data acquisition, processing and transmission; its communication technology uses the NBIoT module to support wireless data transmission, combined with the MQTT protocol to achieve efficient data sending and receiving, and realize real-time transmission of monitoring data and fault status feedback.

[0013] Furthermore, the data acquisition is to convert the analog signal into a digital signal through the ADC interface of STM32, the data acquisition frequency is controlled by the timing interrupt, and the frequency is adjustable; the collected data is packaged into a data packet and sent to the server through the MQTT protocol; the content of the data packet includes: monitoring device ID, sampling time, current value and device status.

[0014] Furthermore, it also includes a fault detection function module for real-time detection of the stability of the communication link; when a communication interruption occurs, the module is automatically restarted, the fault information is recorded, and the data sending frequency is adjusted according to the monitoring scenario.

[0015] The beneficial effects of the present invention are as follows: A snap-on self-power wireless communication current transformer, through the design of the power CT, the core material and structure are optimized to adapt to the energy collection requirements of a wide range of currents from 0A to 120A; the rectification and voltage stabilization circuit adopts a full-bridge rectification design combined with an LC filter circuit to convert the induced AC power into a 12V stable DC voltage to power the wireless communication module and other subsequent devices; and the hysteresis comparator is used to achieve accurate protection against overcurrent and overvoltage to avoid equipment damage; its communication technology uses the NBIoT module to support long-distance, low-power wireless data transmission, combined with the MQTT protocol to achieve efficient data transmission and reception, and the dynamic frequency adjustment supports dynamic adjustment of the data transmission frequency according to the monitoring scenario, optimizing the power consumption and communication efficiency of the equipment. The snap-on design of the snap-on self-power wireless communication current transformer simplifies the installation process and is suitable for a variety of power line environments. The modular layout facilitates equipment expansion and maintenance, and improves the flexibility of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The equivalent circuit diagram of the power CT and the load when the present invention includes a rectifier and filter circuit; Figure 2 It is a diagram of the rectifier circuit (including leakage current) of the present invention; Figure 3 is a filter circuit diagram of the present invention; Figure 4 It is a voltage-stabilizing output circuit diagram of the present invention; Figure 5 The leakage current control circuit diagram of the present invention; Figure 6 It is a characteristic curve diagram of the hysteresis comparator of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be described in detail below with reference to the accompanying drawings.

[0018] The present invention provides a snap-on self-powered wireless communication current transformer. The inductive power module is the core of the system. The current transformer obtains energy from the high-voltage transmission line through the snap-on current transformer through the inductive power CT design and based on the principle of electromagnetic induction. The inductive power module includes core optimization and turns selection. The core is made of high magnetic permeability material (such as silicon steel sheet), and its geometric structure and material properties are optimized so that it has a high energy conversion efficiency when working in a wide current range of 0A to 120A. Through the formula ,in E 2 is the secondary side induced voltage, R 2 is the load resistance, which is adjusted by the number of turns N 2 Optimize the power output and select the best number of turns based on the optimization point of the maximum power output of the transformer.

[0019] The inductive power module, whose power CT is equivalent to a transformer, can be simplified as the excitation reactance X m , equivalent iron loss resistance R m and load impedance R L , the excitation reactance reflects the characteristics of the magnetic circuit, the equivalent iron loss resistance represents the core loss, and the load resistance is the load connected to the output end of the power CT. When the matching condition is met: (common mode matching), CT can output maximum power, and the derived formula is: ; Due to the actual R m X m , which is simplified to: R L X m .

[0020] Rectification circuit design Figure 1 As shown in the figure, the equivalent circuit of the CT and the load including the rectification and filtering is shown. is the sinusoidal current equivalent to the secondary side from the primary side, is the current flowing in the magnetizing reactance, R m is the secondary side equivalent iron loss resistance, R L is the load resistance, C is the filter capacitor. The rectifier filter circuit adopts a full-bridge rectifier design, which consists of four fast recovery diodes to ensure that the induced AC power is efficiently converted into DC power. Assume that the secondary side output voltage is U 2 , the effective value satisfies After rectification and filtering, the output DC voltage , 1.4V is the voltage drop of the rectifier bridge. A transient suppression diode (TVS) is connected to the front end of the rectifier bridge. Its transient suppression voltage is determined by the maximum inductive current of the high-voltage line to protect the subsequent circuit from overvoltage damage. Figure 2 The circuit includes a leakage rectifier circuit. Diodes D1 and D2 are used to rectify the input AC signal to make the current flow in one direction, that is, to convert the AC signal into a DC signal. Diodes D3 and D4 provide leakage protection. Switches T1 and T2 are used to switch the leakage circuit and control the current discharge through external signals.

[0021] In the design of filtering and voltage stabilization circuits, Figure 3 It is a filter circuit. The filter circuit consists of an inductor L and capacitor C The cut-off frequency is given by the formula Determine, ensure that the voltage fluctuation is less than 0.1V, eliminate high-frequency interference, and output a stable DC voltage. The voltage stabilization part uses a linear regulator (such as LM7805) to stabilize the output voltage within the 12V range required by the communication module to ensure that the subsequent module works reliably.

[0022] Analyze the circuit after rectification and filtering, such as Figure 4 As shown in the figure: Voltage regulated output circuit, considering the influence of the rectifier bridge and filter capacitor, the relationship between the equivalent load voltage and the excitation current waveform is as follows: Output voltage Approximately a square wave, the excitation current It is a triangle, and its calculation formula is: ;in, For time; L is the magnetizing inductance, T is the AC cycle. Average load current The calculation needs to take into account the rectifier bridge diode voltage drop of 1.4V, the formula is: ; is the effective value of the transformer secondary side output voltage.

[0023] Figure 5 This is the leakage circuit control diagram. In the leakage control circuit design, when the primary current of the line is too large, causing the secondary side induced current to exceed the design range, the leakage control circuit starts leakage, such as Figure 6 Hysteresis comparator characteristic curve. The control logic of the leakage control circuit adopts the hysteresis comparator design. The hysteresis characteristic is determined by the upper and lower threshold voltages: ,in is the upper threshold voltage; is the reference voltage; is the lower line threshold voltage; is the feedback resistor; is the voltage divider resistor.

[0024] Control the on and off of the MOS tube to achieve rapid response and protection against overcurrent and prevent losses caused by frequent switching.

[0025] Under the condition of pure resistance load, the relationship between the secondary side output power and load of the transformer is: ; in is the core magnetic circuit length of the transformer; The power frequency is 50Hz; is the primary current measurement, N 2 is the number of turns on the secondary side, S is the core cross-sectional area, μ is the magnetic permeability. Through this formula and actual simulation results, it can be seen that the maximum power of the CT is proportional to the square of the primary current, and is optimal when the load resistance is common-mode matched. When the core is not saturated, the power output is relatively stable. When designing, the excitation current needs to be controlled to be less than the saturation current.

[0026] The wireless communication module adopts STM32F103C8T6 microcontroller as the hardware design control core, low power consumption design, built-in ADC module for collecting monitoring data. The communication module integrates NBIOT module, supports long-distance data transmission, and consumes less power than traditional 4G communication modules. Data acquisition converts analog signals into digital signals through the ADC interface of STM32. The data acquisition frequency is controlled by timer interrupt and the frequency is adjustable. The collected data is packaged and sent to the server through MQTT protocol. The data packet content includes: monitoring device ID, sampling time, current value and device status.

[0027] The fault detection function module detects the stability of the communication link in real time. When a communication interruption occurs, the module is automatically restarted and the fault information is recorded. The data transmission frequency is adjusted according to the monitoring scenario. For example, in normal state, it is sent once every 10 minutes; in fault state, it is sent once every minute.

[0028] The following are simulation and experimental application examples of the present invention: Experimental scenario construction: simulate the high-voltage transmission line environment and test the working performance of the inductive power supply module and the wireless communication module. Use a power analyzer to measure the output power and voltage fluctuation of the system. The experimental scenario includes a 220V AC input power supply, an autotransformer, a current booster, and a standard current transformer. The 220V AC input power supply introduces a stable AC power supply from the power grid. The autotransformer can adjust the output voltage online to control the simulated current. The current booster further amplifies the output current of the voltage regulator to simulate a high-voltage and high-current environment. The standard current transformer is connected to the output end of the current booster to verify the accuracy of the experiment.

[0029] The experimental device includes a power supply, a voltage regulator, a current booster and a test circuit, and refers to the verification procedures and national standards for current transformers for measurement to ensure the credibility and repeatability of the experimental data.

[0030] Induction power module test: Test content: simulate three load conditions.

[0031] Test results: The inductive power module simulates three load test conditions respectively. No-load condition: When the primary current reaches the "starting current" (about 10A to 15A), the output voltage rises rapidly and stabilizes at 12.6V. With battery load: When the primary current is small, the output voltage is the voltage across the battery. As the primary current increases, the power module starts to charge the battery, and the final output voltage stabilizes between 12.16V and 12.47V. With battery and development board: Within the rated current range, the inductive power module can stably output 12V DC power and support the normal operation of the development board. The change trend of the secondary current is consistent with that of the primary current. The experiment verifies the stability of the inductive power module under different load conditions, which can meet the power supply requirements of the development board and provide charging support for external loads. Wireless communication module test: Test content: Verify the basic functions and performance of the wireless communication module (NBIOT), including sending data to the server, sending data from the server to the terminal, and variable frequency transmission function.

[0032] Test results: Send data to the server: Use the serial port to connect the wireless communication module to the computer and verify data transmission through the Alibaba Cloud server debugging tool.

[0033] Experimental results: The data content and frequency received by the serial port and the server are consistent, indicating that the module can correctly send data to the server.

[0034] The server sends data to the terminal: Configure the Tencent Cloud platform to forward the data received by the server to the mobile phone in real time (using the "Tencent Lianlian" applet).

[0035] Experimental results: The data displayed on the LCD screen is consistent with the data received by the mobile phone, the delay is low, and the data transmission is normal.

[0036] Variable frequency transmission test: Simulate high-voltage line faults and set abnormal data to trigger the high-frequency data sending function.

[0037] Experimental results: Under normal circumstances, the data transmission frequency is once every 8 seconds, and in the event of a fault, it is increased to once every 2 seconds, verifying the effectiveness of the variable frequency transmission function.

[0038] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the contents disclosed herein. The present application is intended to cover any variations, uses or adaptations of the present application, which follow the general principles of the present application and include common knowledge or customary technical means in the art that are not disclosed in the present application.

[0039] It should be understood that the present application is not limited to the exact construction that has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof.

Claims

1. A snap-on self-powered wireless communication current transformer, characterized in that: include: A snap-on current transformer module, an inductive power supply module, a leakage control module, a sampling compensation module and a wireless communication module; the output end of the snap-on current transformer module is respectively connected to the inductive power supply module and the sampling compensation module, the output end of the inductive power supply module is connected to the leakage control module, the output end of the leakage control module is connected to the sampling compensation module and the wireless communication module; the output end of the sampling compensation module is connected to the wireless communication module; The snap-on current transformer module is used to sense current from a high-voltage transmission line; The induction power module includes a power CT, a rectifier circuit, a filter circuit and a voltage stabilizing circuit. The power CT is used to obtain energy from the secondary side of the coil and charge the lithium battery for energy storage. The rectifier circuit is used to convert the induced AC current into DC power. The filter circuit is used to stabilize the output DC voltage. The leakage control module controls the MOS tube through a hysteresis comparator to prevent overcurrent or overvoltage from damaging subsequent circuits; The sampling and compensation module samples and compensates the current signal, and transmits the collected data to the wireless communication module in real time; The wireless communication module includes an STM32 microcontroller and an NBIOT communication module, which are used to receive the collected current data and transmit it wirelessly to a remote server.

2. The snap-on self-powered wireless communication current transformer according to claim 1, characterized in that: The induction power module optimizes the core structure by using high magnetic permeability materials and selects the optimal number of turns according to the load matching relationship to obtain high conversion efficiency of electromagnetic energy. The expression is as follows: ； in E 2 is the secondary side induced voltage, R 2 is the load resistance; It also enables the inductive power module to stably output 12V DC voltage within the current range of 0A to 120A.

3. The snap-on self-powered wireless communication current transformer according to claim 1, characterized in that: The equivalent circuit of the power CT and the load during rectification and filtering in the inductive power module, the rectification circuit adopts a full-bridge rectification design, composed of four diodes, to ensure that the induced AC power is converted into DC power; assuming that the secondary side output voltage is U 2 , the effective value satisfies ;in is the sinusoidal current equivalent to the secondary side from the primary side, R L is the load resistance; After rectification and filtering, the output DC voltage , 1.4V is the voltage drop of the rectifier bridge; a transient suppression diode TVS is connected to the front end of the rectifier bridge, and its transient suppression voltage is determined by the maximum induced current of the high-voltage line to protect the subsequent circuit from damage by overvoltage.

4. The snap-on self-powered wireless communication current transformer according to claim 1, characterized in that: The rectifier circuit and the voltage stabilizing circuit both adopt a full-bridge rectifier design combined with an LC filter circuit. The LC filter circuit consists of an inductor L and capacitor C The cut-off frequency is given by the formula Determine and ensure that the voltage fluctuation is less than 0.1V, eliminate high-frequency interference, and output a stable DC voltage; a linear voltage regulator is used to convert the induced AC power into a 12V stable DC voltage to power the wireless communication module and other subsequent equipment.

5. The snap-on self-powered wireless communication current transformer according to claim 4, characterized in that: It also includes the analysis of the circuit after rectification and filtering. For the voltage-stabilized output circuit, due to the influence of the rectifier bridge and the filter capacitor, the relationship between the equivalent load voltage and the excitation current waveform is as follows: Considered as a square wave, the excitation current It is a triangle, and its calculation formula is: ; in, For time; L is the magnetizing inductance, T is the AC cycle; average load current The calculation needs to take into account the rectifier bridge diode voltage drop of 1.4V, the formula is: ; is the effective value of the transformer secondary voltage.

6. The snap-on self-powered wireless communication current transformer according to claim 1, characterized in that: The control logic of the leakage control module adopts a hysteresis comparator design, and the hysteresis characteristic is determined by the upper and lower threshold voltages, and the expression is as follows: ;in is the upper threshold voltage; is the reference voltage; is the lower line threshold voltage; is the feedback resistor; is the voltage divider resistor.

7. The snap-on self-powered wireless communication current transformer according to claim 1, characterized in that: Under the condition of pure resistance load, the relationship between the secondary side output power and load of the transformer is: ; in is the core magnetic path length of the transformer, The power frequency is 50Hz, is the primary current measurement, N 2 is the number of turns on the secondary side, S is the core cross-sectional area, μ is the magnetic permeability.

8. The snap-on self-powered wireless communication current transformer according to claim 1, characterized in that: The control core of the wireless communication module is based on the STM32 microcontroller, which controls data acquisition, processing and transmission; its communication technology uses the NBIoT module to support wireless data transmission, combined with the MQTT protocol to realize data sending and receiving, and realize real-time transmission of monitoring data and fault status feedback.

9. The snap-on self-powered wireless communication current transformer according to claim 8, characterized in that: The data acquisition is performed by converting analog signals into digital signals through the ADC interface of STM32. The data acquisition frequency is controlled by a timing interrupt and the frequency is adjustable. The collected data is packaged into a data packet and sent to a server through the MQTT protocol. The content of the data packet includes: monitoring device ID, sampling time, current value and device status.

10. The snap-on self-powered wireless communication current transformer according to claim 1, characterized in that: It also includes a fault detection function module for real-time detection of the stability of the communication link; when a communication interruption occurs, the module is automatically restarted, the fault information is recorded, and the data sending frequency is adjusted according to the monitoring scenario.

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