Autonomous detection and alarm method for high-frequency harmonic abnormity of power grid

Abstract

A power grid high-frequency harmonic abnormity autonomous detection and alarm method is characterized in that a secondary side of a coupling transformer of an ammeter power line carrier communication module is connected in parallel with a high-frequency harmonic detection circuit; the input end of the high-frequency harmonic detection circuit is connected to the secondary side of a coupling transformer of the power line carrier communication module, and the output end is connected with the MCU of the power line carrier communication module; the MCU detects the detection voltage output by the high-frequency harmonic detection circuit in real time and compares the detection voltage with an alarm threshold value, if the detection voltage is continuously larger than the alarm threshold value for a set time, it is judged that high-frequency harmonic waves are abnormal, and the MCU sends first alarm information to a master station; and when the detection voltage is continuously smaller than the alarm threshold value for a set time, it is judged that the high-frequency harmonic wave stops abnormally, and the MCU sends second alarm information and abnormal duration to the master station. According to the invention, automatic detection and remote alarm of the high-frequency harmonic abnormity of 100kHz-500kHz in the power distribution network can be realized, the cost is low, and the practicability is high.

Description

Technical Field

[0001] This invention belongs to the field of power line carrier communication and power quality detection technology, and particularly relates to a method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids based on power line carrier communication. Background Technology

[0002] With the widespread application of power electronics technology, high-frequency harmonic pollution in urban and rural power distribution networks is becoming increasingly prominent. The connection of numerous nonlinear electrical devices such as frequency converters and switching power supplies generates a large number of high-frequency harmonics in the power grid, posing a threat to power equipment. For example, some substandard electric bicycle chargers without power factor correction generate strong ringing harmonics of 150kHz to 400kHz at the moment the switching transistor is turned off, with measured peak voltages reaching 20 to 50V, severely exceeding the interference voltage limits specified in GB 4824-2019 "Limits and Measurement Methods for Radio Frequency Interference Characteristics of Industrial, Scientific and Medical Equipment". These high-frequency harmonics not only interfere with power line carrier communication but also induce high voltages in the secondary winding of the transformer in the power line carrier communication module, causing permanent breakdown of the carrier transmission circuit chip. Several incidents have occurred in Henan, Guangdong, and other regions where high-frequency harmonics generated by substandard electric motorcycle chargers have damaged smart meter carrier modules, resulting in abnormal readings of electricity metering data.

[0003] To prevent high-frequency harmonic anomalies from damaging equipment and affecting the normal operation of the distribution network, some have proposed using power quality analyzers to detect them. However, the deployment cost of specialized power quality analyzers is high, and achieving full coverage at the distribution area level is difficult, resulting in poor practicality. Others have proposed centralized detection using additional sensors and dedicated communication networks, but this approach is difficult to deploy in rural areas, limiting its widespread application. Some power line carrier communication modules use protective circuits, such as transient voltage suppressor diodes (TVS), to suppress transient surges, but this solution is ineffective against persistent high-frequency harmonics. Adding high-frequency harmonic filtering circuits to the carrier channel leads to carrier signal attenuation, affecting communication distance and success rate. Current solutions for high-frequency harmonic detection in urban and rural distribution networks all have shortcomings. Therefore, there is an urgent need for a low-cost, high-reliability high-frequency harmonic detection method that can promptly alert maintenance personnel when harmonic anomalies occur, enabling timely handling by maintenance personnel. Summary of the Invention

[0004] The purpose of this invention is to provide a highly reliable and low-cost method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids includes the following steps:

[0007] A high-frequency harmonic detection circuit is connected in parallel on the secondary side of the coupling transformer of the power line carrier communication module of the electricity meter. The input terminal of the high-frequency harmonic detection circuit is connected to the secondary side of the coupling transformer of the power line carrier communication module, and the output terminal is connected to the MCU of the power line carrier communication module.

[0008] Set alarm thresholds;

[0009] The MCU detects the detection voltage output by the high-frequency harmonic detection circuit in real time and compares the detection voltage with the alarm threshold. If the detection voltage is continuously greater than the alarm threshold for a set time, it is determined that the high-frequency harmonic is abnormal, and the MCU sends the first alarm information to the main station.

[0010] When the detection voltage remains below the alarm threshold for a set time, it is determined that the high-frequency harmonics have stopped abnormally. The MCU records the duration of the abnormality and sends a second alarm message and the duration of the abnormality to the main station.

[0011] In some embodiments, the high-frequency harmonic detection circuit includes a current-limiting circuit, a high-pass filter circuit, a voltage divider circuit, and a detector circuit connected in sequence; the input terminal of the current-limiting circuit is connected to the secondary side of the coupling transformer to limit abnormal current; the high-pass filter circuit is used to filter out power frequency signals and allow high-frequency harmonics of 100kHz to 500kHz to pass through, and the -3dB cutoff frequency of the high-pass filter circuit is 10kHz to 50kHz; the voltage divider circuit is used to reduce voltage; the detector circuit is used to detect the harmonic envelope in the 100kHz to 500kHz frequency band and output a detection voltage.

[0012] In some embodiments, the high-pass filter circuit includes a first capacitor, a first resistor, and a second resistor. The two ends of the first capacitor and the first resistor are respectively connected to the output terminal of the current limiting circuit and ground. One end of the second resistor is connected to the output terminal of the current limiting circuit, and the other end is connected to the voltage divider circuit.

[0013] In some embodiments, the detection circuit includes a Schottky diode, a holding capacitor, and a bleeder resistor. The anode of the Schottky diode is connected to the output terminal of the voltage divider circuit, and the two terminals of the holding capacitor and the bleeder resistor are respectively connected to the cathode of the Schottky diode and ground.

[0014] In some embodiments, the forward voltage drop of the Schottky diode is less than 0.3V.

[0015] In some embodiments, the holding capacitor has a capacitance of 10nF, the discharge resistor has a resistance of 10kΩ, and the time constant formed by the holding capacitor and the discharge resistor is 100μs.

[0016] In some embodiments, the high-frequency harmonic detection circuit further includes an overvoltage protection circuit, which is a TVS protection tube, with one end of the TVS protection tube connected to the output terminal of the detection circuit and the other end grounded.

[0017] In some embodiments, the alarm threshold is set based on the peak voltage on the secondary side of the coupling transformer.

[0018] In some embodiments, when the power line carrier communication module is in the transmitting state, the MCU ignores the harmonic detection results and does not send alarm information.

[0019] As can be seen from the above technical solution, the present invention integrates a high-frequency harmonic detection circuit on the secondary side of the transformer coupled to the power line carrier communication module of the electricity meter, realizing autonomous detection and remote alarm of high-frequency harmonic anomalies from 100kHz to 500kHz. The method of the present invention has the following advantages:

[0020] 1) Accurate early warning to avoid equipment damage: Through high-pass filtering and envelope detection technology of high-frequency harmonic detection circuit, dangerous harmonics can be accurately identified and early warning can be given before equipment damage, which solves the problem that traditional technology is difficult to detect high-frequency harmonics of 100kHz to 500kHz.

[0021] 2) Extremely low hardware cost and easy deployment: Based on the existing power line carrier communication module, only a few components are added, which is inexpensive and can be seamlessly integrated into the existing smart meter carrier communication module. No additional special testing equipment is required, which has extremely high promotion value and is conducive to achieving large-scale deployment at the distribution area level.

[0022] 3) Accurate source tracing and improved operation and maintenance efficiency: Through the electricity meter user information corresponding to the power line carrier communication module, the location of harmonic sources can be accurately located, providing a basis for investigating and dealing with substandard electrical equipment and effectively saving social costs;

[0023] 4) Autonomous operation without external intervention: The high-frequency harmonic detection circuit works independently without relying on an additional communication network. It performs detection during the normal communication gaps of the power line carrier, achieving true autonomous detection and alarm. Attached Figure Description

[0024] To more clearly illustrate the embodiments of the present invention, the accompanying 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 is a structural block diagram of the power line carrier communication module according to an embodiment of the present invention.

[0026] Figure 2This is a circuit diagram of a high-frequency harmonic detection circuit according to an embodiment of the present invention.

[0027] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings. In describing the embodiments of the present invention, for ease of explanation, the drawings illustrating the device structure will be partially enlarged, not according to general proportions. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of the present invention. It should be noted that the drawings are simplified and use non-precise proportions, intended only to facilitate and clearly illustrate the embodiments of the present invention. Additionally, in the description of this application, terms such as "first" and "second" are used only to distinguish descriptions and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Terms such as "positive," "negative," "bottom," "upper," "lower," "front," "rear," "left," and "right" indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, not indicating or implying that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] High-frequency harmonics in the 100kHz–500kHz frequency band of a power distribution network can damage the power line carrier communication module in electricity meters, causing abnormal readings of electricity metering data and affecting the normal operation of the power distribution network. To avoid damage to the power line carrier communication module from high-frequency harmonics, this invention provides a low-cost, embeddable method for autonomous detection and alarm of high-frequency harmonic anomalies within existing power line carrier communication modules. This method enables accurate detection and early warning of dangerous harmonics, preventing damage to power equipment.

[0031] The core idea of ​​this invention is to connect a high-frequency harmonic detection circuit in parallel on the secondary side of the coupling transformer of the power line carrier communication module. The high-frequency harmonic detection circuit performs envelope detection on the high-frequency detection voltage at the hundred kHz level. When the detected voltage exceeds the alarm threshold and continues for a set time (e.g., more than 1 ms), the MCU of the power line carrier communication module reports the alarm information to the main station via the power line carrier, so that maintenance personnel can handle it in time, such as by adding power filter protection for electrical equipment or disabling inferior electrical equipment to eliminate the source of high-frequency harmonic generation.

[0032] Figure 1 This is a structural block diagram of the power line carrier communication module according to an embodiment of the present invention, as shown below. Figure 1 As shown, the power line carrier communication module in this embodiment includes an MCU, a carrier transceiver circuit, and a high-frequency harmonic detection circuit. The MCU and the carrier transceiver circuit are connected, and the carrier transceiver circuit is used for amplifying, transmitting, filtering, and receiving power line carrier signals. In this embodiment, a high-frequency harmonic detection circuit is connected in parallel on the secondary side of the coupling transformer (T0) of the power line carrier communication module. The input terminal of the high-frequency harmonic detection circuit is connected to the secondary side of the coupling transformer, and the output terminal is connected to the ADC pin of the MCU or the input terminal of the comparator, used to detect high-frequency harmonic anomalies in the range of 100kHz to 500kHz.

[0033] like Figure 2 As shown, the high-frequency harmonic detection circuit of this embodiment includes a current-limiting circuit, a high-pass filter circuit, a voltage divider circuit, and a detector circuit connected in sequence. The current-limiting circuit is used for current limiting protection. Its input is connected to the secondary side of the coupling transformer T0 to limit abnormal current and protect subsequent circuits. In this embodiment, the current-limiting circuit uses a current-limiting resistor Rs. The current-limiting circuit can be a single current-limiting resistor or multiple current-limiting resistors connected in series, and the value can be set according to the power capacity of the current-limiting resistors. Considering power capacity and reliability, the current-limiting resistor Rs in this embodiment is two 1206 packaged 22Ω resistors connected in series, with a total resistance of 44Ω.

[0034] The high-pass filter circuit in this embodiment includes a first capacitor Chp, a first resistor Rshunt, and a second resistor Rhp. The first capacitor Chp and the first resistor Rshunt are a parallel capacitor and a parallel resistor, respectively. One end of the first capacitor Chp is connected to the output of the current-limiting circuit, and the other end is grounded. One end of the first resistor Rshunt is connected to the output of the current-limiting circuit, and the other end is grounded. The first capacitor Chp and the first resistor Rshunt are connected between the current-limiting circuit and the second resistor Rhp. One end of the second resistor Rhp is connected to the output of the current-limiting circuit, and the other end is connected to the voltage divider circuit. The -3dB cutoff frequency of the high-pass filter circuit is set to 10kHz to 50kHz to filter out power frequency signals and allow high-frequency harmonics of 100kHz to 500kHz to pass through. In this embodiment, the first capacitor Chp is a 1nF capacitor, and the first resistor Rshunt is a 15kΩ resistor. The high-pass filter circuit formed by these two components has a -3dB cutoff frequency of 10.6kHz, which allows high-frequency harmonics from 100kHz to 500kHz to pass smoothly, while attenuating the 50Hz power frequency signal by about 40dB.

[0035] A voltage divider circuit is used to reduce the voltage of high-voltage harmonic signals, making it acceptable to the MCU or comparator. In this embodiment, the voltage divider circuit includes a first voltage divider resistor R1 and a second voltage divider resistor R2. The first voltage divider resistor R1 is a series resistor connected between the high-pass filter circuit and the detector circuit. The second voltage divider resistor R2 is a parallel resistor, with one end connected between the first voltage divider resistor R1 and the detector circuit, and the other end grounded. Through the first voltage divider resistor R1 and the second voltage divider resistor R2, the high-voltage harmonic signal is reduced to a level acceptable to the microcontroller unit (MCU) or comparator. In this embodiment, the resistance of the first voltage divider resistor R1 is 90kΩ, and the resistance of the second voltage divider resistor R2 is 10kΩ, forming a 10:1 voltage divider ratio. When the peak voltage on the secondary side of the coupling transformer is 24V, the peak voltage after voltage division is approximately 2.4V, which is within the safe operating range of the MCU.

[0036] The detection circuit in this embodiment includes a Schottky diode Dshottky, a holding capacitor Chold, and a bleeder resistor Rdis, wherein the forward voltage drop of the Schottky diode Dshottky is less than 0.3V. The detection circuit outputs a detection voltage Vdc to the MCU. The MCU compares the detection voltage with the alarm threshold and sends an alarm signal to the master station via power line carrier based on the comparison result. The positive terminal of the Schottky diode Dshottky is connected to the output terminal of the voltage divider circuit. One end of the holding capacitor Chold is connected to the negative terminal of the Schottky diode Dshottky, and the other end is grounded. Similarly, one end of the bleeder resistor Rdis is connected to the negative terminal of the Schottky diode Dshottky, and the other end is grounded. This embodiment uses a BAT54 Schottky diode, the capacitance of the holding capacitor Chold is 10nF, and the resistance of the bleeder resistor Rdis is 10kΩ. By maintaining a time constant τ = 100μs formed by capacitor Chold and bleed resistor Rdis, the envelope waveform can be effectively smoothed for harmonics in the 100kHz to 500kHz frequency band (period 2 to 10μs), while maintaining sufficient response speed to determine the continued existence of harmonics.

[0037] Preferably, in some embodiments, the high-frequency harmonic detection circuit further includes an overvoltage protection circuit, which is located at the output terminal of the detector circuit and is used for overvoltage protection. In this embodiment, the overvoltage protection circuit is a TVS diode, with one end of the TVS diode connected to the output terminal of the detector circuit and the other end grounded.

[0038] like Figure 1 As shown, the power line carrier communication module couples the carrier signal to the power line through a coupling transformer T0 and a safety capacitor C0, and also receives signals from the power line. In this embodiment, the safety capacitor C0 is a 0.01μF safety capacitor, the turns ratio of the coupling transformer T0 is 1:1, and both the primary and secondary inductances are 20μH. Commonly used power line carrier linear drive amplifiers (such as TI's THS6212) have a maximum withstand voltage of 28V. If the voltage on the secondary side of the coupling transformer T0 continuously exceeds 28V due to a high-frequency detection voltage on the power line, it may damage the carrier communication chip. The MCU in this embodiment uses a power line carrier communication chip, model WTZ30S, from Zhuhai Zhonghui Microelectronics Co., Ltd., which has a built-in comparator and ADC sampling function. The comparator threshold is set to 2.1V (2.4V minus the 0.3V Schottky diode voltage drop), and the detection voltage Vdc can also be sampled through the MCU's ADC pin and a threshold comparison performed. Under a working voltage of 3.3V, the Xunlei PSD series TVS protection tube is selected to prevent overvoltage surges.

[0039] To avoid damage to devices caused by high-frequency detection voltage, the autonomous detection and alarm method for high-frequency harmonic anomalies in the power grid in this embodiment includes the following steps:

[0040] A high-frequency harmonic detection circuit is connected in parallel on the secondary side of the coupling transformer of the power line carrier communication module. The input of the high-frequency harmonic detection circuit is connected to the secondary side of the coupling transformer T0, and the output is connected to the MCU, such as the output being connected to the ADC pin or comparator input of the MCU.

[0041] An alarm threshold Vth is set. Considering a safety margin, this embodiment sets the alarm threshold Vth based on the peak voltage of 24V on the secondary side of the coupling transformer. When the voltage on the secondary side of the coupling transformer, i.e., the input voltage of the high-frequency harmonic detection circuit, exceeds 24V, it becomes the alarm threshold. Taking into account the voltage division ratio of the voltage divider circuit and the voltage drop of the Schottky diode, the resistance values ​​of the current-limiting resistor Rs in the current-limiting circuit and the second resistor Rhp in the high-pass filter circuit are much smaller than the resistance values ​​of the voltage-dividing resistors (R1, R2) in the voltage divider circuit. Therefore, the current-limiting resistor Rs and the second resistor... The voltage drop across Rhp is negligible. After passing through a 10:1 voltage divider circuit, the voltage entering the Schottky diode Dshottky is 2.4V. Subtracting the forward voltage drop of the Schottky diode Dshottky (0.3V), the alarm threshold Vth is set as follows: peak voltage on the secondary side of the coupling transformer / voltage division ratio of the voltage divider circuit minus the forward voltage drop of the Schottky diode = 24 / 10 - 0.3 = 2.1V. Furthermore, the alarm threshold can be adjusted based on actual debugging results or set according to the resistance value of the voltage divider circuit; no limitation is made here.

[0042] The MCU monitors the detection voltage Vdc output by the high-frequency harmonic detection circuit in real time and compares the detection voltage Vdc with the alarm threshold Vth. If the detection voltage Vdc is continuously greater than the alarm threshold Vth for a set time, such as when Vdc is continuously greater than Vth for 1ms, it is determined that there is a high-frequency harmonic anomaly. The MCU sends the first alarm message "High-frequency harmonic anomaly occurs" to the master station through the power line carrier to notify the master station that a high-frequency harmonic anomaly has occurred.

[0043] When the detection voltage Vdc is continuously less than the alarm threshold Vth for a set time, such as when Vdc is continuously less than Vth for 1ms, it is determined that the high-frequency harmonic has stopped abnormally. The MCU records the abnormal duration T1 and sends the second alarm message "high-frequency harmonic has stopped abnormally" and the abnormal duration T1 to the master station through the power line carrier.

[0044] In some embodiments, when the power line carrier communication module is in the transmitting state, the MCU ignores the harmonic detection results to avoid interference from the power line carrier communication module's own carrier signal with the harmonic detection.

[0045] This invention connects a high-frequency harmonic detection circuit in parallel on the secondary side of the coupling transformer of the power line carrier communication module. Without the need for additional dedicated detection equipment, it can accurately identify dangerous harmonics and provide early warnings before equipment damage occurs. This enables rapid location and mitigation of harmonic sources. Moreover, the high-frequency harmonic detection circuit has a simple structure and, compared to dedicated instruments, has advantages such as low hardware cost, high detection accuracy, and ease of integration. It is suitable for large-scale deployment of smart meter carrier communication modules.

[0046] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids, characterized in that, Includes the following steps: A high-frequency harmonic detection circuit is connected in parallel on the secondary side of the coupling transformer of the power line carrier communication module of the electricity meter. The input terminal of the high-frequency harmonic detection circuit is connected to the secondary side of the coupling transformer of the power line carrier communication module, and the output terminal is connected to the MCU of the power line carrier communication module. Set alarm thresholds; The MCU detects the detection voltage output by the high-frequency harmonic detection circuit in real time and compares the detection voltage with the alarm threshold. If the detection voltage is continuously greater than the alarm threshold for a set time, it is determined that the high-frequency harmonic is abnormal, and the MCU sends the first alarm information to the main station. When the detection voltage remains below the alarm threshold for a set time, it is determined that the high-frequency harmonics have stopped abnormally. The MCU records the duration of the abnormality and sends a second alarm message and the duration of the abnormality to the main station.

2. The method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids as described in claim 1, characterized in that: The high-frequency harmonic detection circuit includes a current-limiting circuit, a high-pass filter circuit, a voltage divider circuit, and a detector circuit connected in sequence. The input terminal of the current-limiting circuit is connected to the secondary side of the coupling transformer to limit abnormal current. The high-pass filter circuit is used to filter out power frequency signals and allow high-frequency harmonics of 100kHz to 500kHz to pass through. The -3dB cutoff frequency of the high-pass filter circuit is 10kHz to 50kHz. The voltage divider circuit is used to reduce the voltage. The detector circuit is used to detect the harmonic envelope in the 100kHz to 500kHz frequency band and output a detection voltage.

3. The method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids as described in claim 2, characterized in that: The high-pass filter circuit includes a first capacitor, a first resistor, and a second resistor. The two ends of the first capacitor and the first resistor are respectively connected to the output terminal of the current limiting circuit and ground. One end of the second resistor is connected to the output terminal of the current limiting circuit, and the other end is connected to the voltage divider circuit.

4. The method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids as described in claim 1, characterized in that: The detection circuit includes a Schottky diode, a holding capacitor, and a bleed resistor. The positive terminal of the Schottky diode is connected to the output terminal of the voltage divider circuit. The two ends of the holding capacitor and the bleed resistor are respectively connected to the negative terminal of the Schottky diode and ground.

5. The method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids as described in claim 4, characterized in that: The forward voltage drop of the Schottky diode is less than 0.3V.

6. The method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids as described in claim 4, characterized in that: The holding capacitor has a capacitance of 10nF, the discharge resistor has a resistance of 10kΩ, and the time constant formed by the holding capacitor and the discharge resistor is 100μs.

7. The method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids as described in claim 2, characterized in that: The high-frequency harmonic detection circuit also includes an overvoltage protection circuit, which is a TVS protection tube. One end of the TVS protection tube is connected to the output terminal of the detection circuit, and the other end is grounded.

8. The method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids as described in claim 1, characterized in that: The alarm threshold is set based on the peak voltage on the secondary side of the coupling transformer.

9. The method for autonomous detection and alarm of high-frequency harmonic anomalies in power grids as described in claim 1, characterized in that: When the power line carrier communication module is in the transmitting state, the MCU ignores the harmonic detection results and does not send alarm information.

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