AC overhead ground wire magnetic induction energy taking method based on multi-channel frequency division rectification

Abstract

The invention discloses an alternating-current overhead ground wire magnetic induction energy taking method based on multichannel frequency division rectification. The method comprises the steps that voltage signals at the two ends of a ground wire insulator are acquired; inputting the voltage signal into an overvoltage protection circuit in the energy taking circuit for overvoltage protection, and outputting a processed voltage signal; harmonic signals with different frequencies are separated from the processed voltage signals through a frequency division module based on a band-pass filter bank; rectifying power frequency signals in the harmonic signals with different frequencies into direct current signals after low-frequency rectification by utilizing a low-frequency rectification module, and rectifying frequency multiplication signals into direct current signals after high-frequency rectification by utilizing a high-frequency rectification module; and combining the low-frequency rectified direct-current signal and the high-frequency rectified direct-current signal through a parallel-connection circuit, and outputting a combined direct-current signal. According to the invention, the problem that the power consumption of an on-line monitoring device is difficult to support due to insufficient energy-taking power when the current of the wire is small in the existing ground wire power-taking method can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of high voltage, and particularly to an AC overhead ground wire magnetic induction energy harvesting method based on multi-channel frequency division rectification. Background Art

[0002] Online monitoring of overhead transmission lines is an important means to ensure the safe and reliable operation of the power grid and a key link to facilitate the digital and intelligent transformation of the power grid. However, the existing online monitoring technologies cannot well meet the actual needs of transmission lines. One important reason is that the power supply problem restricts the application of online monitoring devices. Currently, the most widely used solar power supply is severely dependent on the weather, and the energy harvesting power is poor under bad weather conditions such as rain, snow, and fog. In winter in northern China, the solar panels are extremely easy to be covered by ice and snow and even unable to generate electricity. The current transformers installed on high-voltage wires can supply power to high-voltage end equipment, but cannot supply power to the devices on the towers.

[0003] Overhead lines with voltage levels of 110 kV and above in China are generally equipped with two ground wires for lightning protection. Due to the action of mutual inductance and capacitance, there are induced voltages or induced currents from the conductors on the ground wires. The electromagnetic coupling between the conductors and the ground wires is very strong. The Zhejiang Electric Power Company observed that the induced voltage on a certain 500 kV sectional insulated ground wire exceeded 15 V. Therefore, the ground wire is a natural power source for overhead line online monitoring equipment. A large number of studies on ground wire energy harvesting have been carried out at home and abroad, and relevant ground wire energy harvesting schemes and energy harvesting circuits have been proposed by units such as Chongqing University and Fuzhou University. According to the energy harvesting principle, ground wire energy harvesting can be divided into two categories: magnetic induction energy harvesting and electrostatic induction energy harvesting. Electrostatic induction energy harvesting requires the ground wire to be insulated along the line, which involves large-scale ground wire transformation, so it is rarely used. Magnetic induction energy harvesting has become the mainstream ground wire energy harvesting scheme because of its simple implementation and considerable energy harvesting power in most cases. However, the power of magnetic induction energy harvesting is proportional to the square of the conductor current, and the energy harvesting power is still not ideal when the line is lightly loaded. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related technologies to some extent.

[0005] The present invention proposes an AC overhead ground wire magnetic induction energy harvesting method based on multi-channel frequency division rectification to improve the energy harvesting power of ground wire magnetic induction energy harvesting and make full use of the electromagnetic energy in the ground wire.

[0006] Another object of the present invention is to propose an AC overhead ground wire magnetic induction energy harvesting system based on multi-channel frequency division rectification.

[0007] To achieve the above object, on the one hand, the present invention proposes an AC overhead ground wire magnetic induction energy harvesting method based on multi-channel frequency division rectification, including:

[0008] Obtaining the voltage signal across the ground wire insulator;

[0009] Input the voltage signal into the over-voltage protection circuit in the energy harvesting circuit for over-voltage protection output processing of the voltage signal;

[0010] Separate harmonic signals of different frequencies from the processed voltage signal through a frequency division module based on a bandpass filter bank;

[0011] Use a low-frequency rectification module to rectify the power frequency signal in the harmonic signals of different frequencies into a low-frequency rectified DC signal, and use a high-frequency rectification module to rectify the double-frequency signal into a high-frequency rectified DC signal;

[0012] Merge the low-frequency rectified DC signal and the high-frequency rectified DC signal through a parallel merging circuit to output the merged DC signal.

[0013] The AC overhead ground wire magnetic induction energy harvesting method based on multi-channel frequency division rectification in the embodiment of the present invention may further have the following additional technical features:

[0014] In an embodiment of the present invention, the method further includes:

[0015] Determine the harmonic components with amplitudes greater than a preset threshold in the line based on the oscillogram information in the substation;

[0016] Determine the device parameters of the frequency division module and the rectification module in the energy harvesting circuit according to the harmonic frequencies corresponding to the harmonic components;

[0017] Comprehensively determine the number of frequency division circuits according to the power consumption and cost factors of the electrical device;

[0018] Select a suitable energy harvesting site for on-line energy harvesting of the ground wire according to the device parameters and the number of frequency division circuits.

[0019] In an embodiment of the present invention, the frequency division module based on a bandpass filter bank is composed of a capacitor-inductor filter. It is necessary to design a capacitor-inductor circuit matching the resonance point for each frequency, and determine the capacitance and inductance parameters of the bandpass filter bank according to the harmonic characteristics of different lines. The corresponding calculation formula is:

[0020]

[0021] In the formula, f is the target frequency processed by the filter, L is the inductance value in the filter, and C is the capacitance value in the filter.

[0022] In an embodiment of the present invention, the power frequency is rectified by a diode full bridge rectifier, and a large-capacity electrolytic capacitor is combined to suppress low-frequency ripple; the double-frequency signal is rectified by a fast-recovery diode, and an inductor, a small-capacity ceramic capacitor and a ferrite bead are combined for filtering; among them, the filtering needs to meet the cut-off frequency higher than the target frequency of the channel.

[0023] In one embodiment of the present invention, before utilizing and combining the parallel circuit, the method further includes:

[0024] A Schottky diode is connected in series on the output channel of each rectification module to prevent current backflow, and a small-value resistor is added for dynamic current sharing; the total output current of the parallel circuit is the sum of the output currents of each rectification module.

[0025] Another object of the present invention is to provide an AC overhead ground wire magnetic induction energy harvesting system based on multi-channel frequency division rectification, including:

[0026] A voltage signal acquisition module for acquiring the voltage signal across the ground wire insulator;

[0027] An overvoltage protection module for inputting the voltage signal into the overvoltage protection circuit in the energy harvesting circuit for overvoltage protection output processing of the voltage signal;

[0028] A signal frequency division module for separating harmonic signals of different frequencies from the processed voltage signal through a frequency division module based on a bandpass filter bank;

[0029] A signal rectification module for rectifying the power frequency signal in the harmonic signals of different frequencies into a low-frequency rectified DC signal by using a low-frequency rectification module, and rectifying the double-frequency signal into a high-frequency rectified DC signal by using a high-frequency rectification module;

[0030] A signal combination module for combining the low-frequency rectified DC signal and the high-frequency rectified DC signal through a parallel combination circuit and outputting the combined DC signal.

[0031] The AC overhead ground wire magnetic induction energy harvesting method and system based on multi-channel frequency division rectification according to the embodiments of the present invention make full use of the power frequency induction voltage and harmonic induction voltage on the AC overhead ground wire to achieve high-power on-line power extraction, and solve the problems of insufficient power extraction when the wire current is small and difficulty in supporting the power consumption of on-line monitoring devices in the existing ground wire power extraction methods.

[0032] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0033] The above and / or additional aspects and advantages of the present invention will become apparent and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0034] Figure 1 is a flowchart of an AC overhead ground wire magnetic induction energy harvesting method based on multi-channel frequency division rectification according to an embodiment of the present invention;

[0035] Figure 2It is the top-level structure diagram of the power acquisition circuit using the power frequency and harmonic induction of the ground wire according to an embodiment of the present invention;

[0036] Figure 3 It is the application flowchart according to an embodiment of the present invention;

[0037] Figure 4 It is the structure diagram of the AC overhead ground wire magnetic induction power acquisition system based on multi-channel frequency division rectification according to an embodiment of the present invention. Specific embodiments

[0038] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0039] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0040] The AC overhead ground wire magnetic induction power acquisition method and system based on multi-channel frequency division rectification proposed according to an embodiment of the present invention will be described below with reference to the drawings.

[0041] Figure 1 It is the flowchart of the AC overhead ground wire magnetic induction power acquisition method based on multi-channel frequency division rectification according to an embodiment of the present invention. As Figure 1 shown, the method includes:

[0042] S1, obtaining the voltage signal at both ends of the ground wire insulator;

[0043] S2, inputting the voltage signal into the overvoltage protection circuit in the power acquisition circuit for overvoltage protection output processing of the voltage signal;

[0044] S3, separating harmonic signals of different frequencies from the processed voltage signal through a frequency division module based on a band-pass filter bank;

[0045] S4, rectifying the power frequency signal in the harmonic signals of different frequencies into a low-frequency rectified DC signal by using a low-frequency rectification module, and rectifying the double-frequency signal into a high-frequency rectified DC signal by using a high-frequency rectification module;

[0046] S5, merging the low-frequency rectified DC signal and the high-frequency rectified DC signal through a parallel merging circuit to output the merged DC signal.

[0047] First, there will be harmonic currents such as the third and fifth harmonics in the wire. Although the amplitude of the harmonic current is significantly smaller than that of the power frequency current, the harmonic frequency is high, and the amplitude of the harmonic induced voltage coupled to the ground wire is also relatively high. Table 1 shows the harmonic conditions of the wire current measured in a certain substation. Taking the data in Table 1 as an example, the amplitude of the induced voltage generated by the 5th harmonic on the ground wire is approximately equal to that generated by a 500A power frequency current, the amplitude of the induced voltage generated by the 5th harmonic on the ground wire is approximately equal to that generated by a 240A power frequency current, the amplitude of the induced voltage generated by the 11th harmonic on the ground wire is approximately equal to that generated by a 600A power frequency current, and the amplitude of the induced voltage generated by the 13th harmonic on the ground wire is approximately equal to that generated by a 650A power frequency current. Therefore, integrating and utilizing the voltages generated by each harmonic can significantly improve the energy extraction power of the ground wire.

[0048] To make full use of the induced harmonics of each order in the ground wire, the present invention correspondingly designs an energy extraction circuit based on multi-channel frequency division rectification. Taking the line harmonic conditions corresponding to Table 1 as an example, its top-level structure diagram is as Figure 2 shown.

[0049] Table 1

[0050]

[0051] Its basic principle is to separate different frequency components in the mixed-frequency voltage at both ends of the ground wire insulator into independent channels and rectify them independently, and finally combine and output the rectified DC voltage to improve the multi-frequency energy capture efficiency. Figure 2 The overvoltage protection circuit therein is a protection circuit structure that can comprehensively consider lightning overvoltage and power frequency overvoltage caused by wire short circuit. Figure 2 The frequency division module based on the band-pass filter bank therein is composed of a capacitor-inductor filter, and a capacitor-inductor circuit with a resonance point matching for each frequency needs to be designed. The harmonic characteristics of different AC lines may vary, and the capacitance and inductance parameters of the band-pass filter bank need to be determined according to the harmonic characteristics of different lines. The corresponding calculation formula is shown in Equation 1.

[0052]

[0053] In the formula, f is the target frequency processed by the filter, L is the inductance value in the filter, and C is the capacitance value in the filter.

[0054] After frequency division is completed, customized rectification design needs to be carried out for different frequencies to improve the energy conversion rate. The power frequency of 50 Hz is relatively low, and the conduction loss is the main factor during rectification, while the switching loss can be ignored. Therefore, a conventional diode full-bridge rectifier is adopted, and a large-capacity electrolytic capacitor is used to suppress low-frequency ripple. For the relatively high frequencies corresponding to harmonics, the switching loss and electromagnetic interference problems need to be considered. Therefore, the conventional diodes in the rectifier bridge are replaced with fast-recovery diodes, and inductors, small-capacity ceramic capacitors, and ferrite beads are used for filtering. At this time, the filtering needs to meet the condition that the cut-off frequency is slightly higher than the target frequency of the channel. After each rectification module outputs a DC voltage, an energy merging circuit is used to merge the energy. At this time, Schottky diodes need to be connected in series on the output channels of each rectification module to prevent current reflux, and small-value resistors (such as 0.1 Ω) are added for dynamic current sharing. The total output current of the energy merging circuit is the sum of the output currents of each rectification module, expanding the energy taken.

[0055] Further, the application process of the present invention is as Figure 3 shown. Determine the harmonic components with amplitudes greater than the preset threshold in the line based on the recorded wave information in the substation; determine the device parameters of the frequency division module and the rectification module in the energy-taking circuit according to the harmonic frequencies corresponding to the harmonic components; comprehensively determine the number of frequency division circuits according to the power consumption and cost factors of the electrical device; select a suitable energy-taking site for on-line energy taking from the ground wire according to the device parameters and the number of frequency division circuits.

[0056] Specifically, first, determine the obvious harmonic components in the line based on information such as recorded waves in the substation, and determine the device parameters of the frequency division module and the rectification module in the energy-taking circuit according to the corresponding harmonic frequencies. The number of required frequency division circuits needs to be comprehensively determined according to factors such as the power consumption and cost of the electrical device. Then select a suitable energy-taking site for on-line power taking from the ground wire. Taking the operation mode of one ground wire grounded at each pole and one ground wire insulated in sections as an example, the farther the energy-taking device is from the grounding point of the section-insulated ground wire, the greater the energy-taking power.

[0057] For the line harmonic conditions listed in Table 1, the energy-taking power of the present invention has increased by 27% compared with only using power frequency for energy taking. Therefore, the technical solution of the present invention can effectively increase the energy-taking power of the ground wire induction and realize the full utilization of the ground wire induction energy.

[0058] According to the AC overhead ground wire magnetic induction energy-taking method based on multi-channel frequency division rectification of the embodiment of the present invention, the power frequency induction voltage and harmonic induction voltage on the AC overhead ground wire are fully utilized to realize high-power on-line power taking, and solve the problems of insufficient energy-taking power and difficulty in supporting the power consumption of on-line monitoring devices in the existing ground wire power-taking methods when the wire current is small.

[0059] Further, as Figure 4 shown, the present invention proposes an AC overhead ground wire magnetic induction energy-taking system 10 based on multi-channel frequency division rectification, including:

[0060] A voltage signal acquisition module 100 is used to acquire the voltage signal across the ground wire insulator;

[0061] An overvoltage protection module 200 is used to input the voltage signal into the overvoltage protection circuit in the energy harvesting circuit for overvoltage protection output processing of the voltage signal;

[0062] A signal frequency division module 300 is used to separate harmonic signals of different frequencies from the processed voltage signal through a frequency division module based on a band-pass filter bank;

[0063] A signal rectification module 400 is used to rectify the power frequency signal in the harmonic signals of different frequencies into a low-frequency rectified DC signal by using a low-frequency rectification module, and rectify the frequency-doubled signal into a high-frequency rectified DC signal by using a high-frequency rectification module;

[0064] A signal merging module 500 is used to merge the low-frequency rectified DC signal and the high-frequency rectified DC signal through a parallel merging circuit and output the merged DC signal.

[0065] Further, it further includes:

[0066] Determine the harmonic components with amplitudes greater than a preset threshold in the line based on the oscillographic recording information in the substation;

[0067] Determine the device parameters of the frequency division module and the rectification module in the energy harvesting circuit according to the harmonic frequencies corresponding to the harmonic components;

[0068] Comprehensively determine the number of frequency division circuits according to the power consumption and cost factors of the electrical device;

[0069] Select a suitable energy harvesting site for on-line energy harvesting of the ground wire according to the device parameters and the number of frequency division circuits.

[0070] Further, the frequency division module based on the band-pass filter bank is composed of a capacitor-inductor filter. It is necessary to design a capacitor-inductor circuit with a resonant point matching for each frequency, and determine the capacitance and inductance parameters of the band-pass filter bank according to the harmonic characteristics of different lines. The corresponding calculation formula is:

[0071]

[0072] In the formula, f is the target frequency processed by the filter, L is the inductance value in the filter, and C is the capacitance value in the filter.

[0073] Further, the power frequency is rectified by a diode full bridge rectifier, and a large-capacity electrolytic capacitor is combined to suppress low-frequency ripple; the frequency-doubled signal is rectified by a fast-recovery diode, and an inductor, a small-capacity ceramic capacitor and a ferrite bead are combined for filtering; among them, the filtering needs to meet the cut-off frequency higher than the target frequency of the channel.

[0074] Further, before the signal combining module 500, it further includes: a backflow prevention module, configured to:

[0075] A Schottky diode is connected in series on each output channel of the rectification module to prevent current backflow, and a small-value resistor is added for dynamic current sharing; the total output current of the combined circuit is the sum of the output currents of each rectification module.

[0076] According to the AC overhead ground wire magnetic induction energy harvesting system based on multi-channel frequency division rectification of the embodiment of the present invention, the power frequency induction voltage and harmonic induction voltage on the AC overhead ground wire are fully utilized to achieve high-power on-line power harvesting, and solve the problems of insufficient power harvesting when the wire current is small in the existing ground wire power harvesting method and it is difficult to support the power consumption of on-line monitoring devices.

[0077] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0078] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

Claims

1. A method for obtaining energy from AC overhead ground wire magnetic induction based on multi-channel frequency division rectification, characterized in that: include: Obtain voltage signals at both ends of the ground wire insulator; Input the voltage signal into the overvoltage protection circuit in the energy extraction circuit for overvoltage protection and output the voltage signal after the overvoltage protection is processed; The processed voltage signal is separated into harmonic signals of different frequencies through a frequency division module based on a bandpass filter group; The power frequency signal in the harmonic signal of different frequencies is rectified into a low-frequency rectified DC signal by using a low-frequency rectifier module, and the frequency-multiplied signal is rectified into a high-frequency rectified DC signal by using a high-frequency rectifier module; The DC signal after low-frequency rectification and the DC signal after high-frequency rectification are combined through the parallel combining circuit to output a combined DC signal.

2. The method according to claim 1, characterized in that: The method further comprises: Determine the harmonic components in the line with amplitudes greater than a preset threshold based on the recorded information in the substation; Determine the device parameters of the frequency division module and the rectifier module in the energy extraction circuit according to the harmonic frequency corresponding to the harmonic component; The number of frequency division circuits is determined comprehensively based on the power consumption and cost factors of the electrical device; According to the device parameters and the number of frequency division circuits, a suitable energy acquisition point is selected for online energy acquisition of the ground line.

3. The method according to claim 1, characterized in that The frequency division module based on the bandpass filter group is composed of a capacitor-inductor filter. It is necessary to design a capacitor-inductor circuit with resonance point matching for each frequency. The capacitor and inductor parameters of the bandpass filter group are determined according to the harmonic characteristics of different lines. The corresponding calculation formula is: Where f is the target frequency processed by the filter, L is the inductance value in the filter, and C is the capacitance value in the filter.

4. The method according to claim 1, characterized in that The power frequency is rectified by a full-bridge diode, combined with a large-capacity electrolytic capacitor to suppress low-frequency ripple; the doubled frequency signal is rectified by a fast recovery diode, combined with an inductor, a small-capacity ceramic capacitor and a ferrite bead for filtering; the filtering must meet the requirement that the cut-off frequency is higher than the target frequency of the channel.

5. The method according to claim 1, characterized in that Before using the parallel-connecting circuit, the method further includes: A Schottky diode is connected in series on the output channel of each rectifier module to prevent current backflow, and a small resistance resistor is added for dynamic current sharing; the total output current of the parallel circuit is the sum of the output currents of each rectifier module.

6. An AC overhead ground wire magnetic induction energy harvesting system based on multi-channel frequency division rectification, characterized in that: include: A voltage signal acquisition module is used to acquire voltage signals at both ends of the ground wire insulator; An overvoltage protection module is used to input a voltage signal into an overvoltage protection circuit in an energy-taking circuit for overvoltage protection and output a voltage signal after the overvoltage protection is processed; A signal frequency division module is used to separate the processed voltage signal into harmonic signals of different frequencies through a frequency division module based on a bandpass filter group; A signal rectifier module, used to rectify the power frequency signal in the harmonic signal of different frequencies into a low-frequency rectified DC signal using a low-frequency rectifier module, and to rectify the frequency-multiplied signal into a high-frequency rectified DC signal using a high-frequency rectifier module; The signal merging module is used to merge the low-frequency rectified DC signal and the high-frequency rectified DC signal through a parallel merging circuit to output a merged DC signal.

7. The system according to claim 6, characterized in that Also includes: Determine the harmonic components in the line with amplitudes greater than a preset threshold based on the recorded information in the substation; Determine the device parameters of the frequency division module and the rectifier module in the energy extraction circuit according to the harmonic frequency corresponding to the harmonic component; The number of frequency division circuits is determined comprehensively based on the power consumption and cost factors of the electrical device; According to the device parameters and the number of frequency division circuits, a suitable energy acquisition point is selected for online energy acquisition of the ground line.

8. The system according to claim 6, characterized in that The frequency division module based on the bandpass filter group is composed of a capacitor-inductor filter. It is necessary to design a capacitor-inductor circuit with resonance point matching for each frequency. The capacitor and inductor parameters of the bandpass filter group are determined according to the harmonic characteristics of different lines. The corresponding calculation formula is: Where f is the target frequency processed by the filter, L is the inductance value in the filter, and C is the capacitance value in the filter.

9. The system according to claim 6, characterized in that The power frequency is rectified by a full-bridge diode, combined with a large-capacity electrolytic capacitor to suppress low-frequency ripple; the doubled frequency signal is rectified by a fast recovery diode, combined with an inductor, a small-capacity ceramic capacitor and a ferrite bead for filtering; the filtering must meet the requirement that the cut-off frequency is higher than the target frequency of the channel.

10. The system according to claim 6, characterized in that Before the signal merging module, it also includes: a backflow prevention module, which is used to: A Schottky diode is connected in series on the output channel of each rectifier module to prevent current backflow, and a small resistance resistor is added for dynamic current sharing; the total output current of the parallel circuit is the sum of the output currents of each rectifier module.

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