An overhead ground wire magnetic induction energy harvesting device based on capacitance compensation

Abstract

The present invention discloses an overhead ground wire magnetic induction energy harvesting device based on capacitor compensation, which is used to draw power from online monitoring equipment of overhead lines. The overhead line includes an ordinary ground wire and an OPGW ground wire, and its wiring method is as follows: the ordinary ground wire is segmented and single-point grounded, and the OPGW ground wire is grounded tower by tower. The energy harvesting device draws power from the parallel gap of the ground wire insulator and includes a decoupling inductor, a varistor, and a rectifier and voltage-stabilizing module, wherein the decoupling inductor and the varistor are connected in series to form an overvoltage protection module and are connected in parallel with the parallel gap. The device also includes a compensation capacitor, which is connected in series with the rectifier and voltage-stabilizing module and then in parallel with the varistor. The compensation capacitor is used to increase the theoretical maximum power of the energy harvesting. By introducing the compensation capacitor into the ground wire energy harvesting device, the influence of the inductance on the energy harvesting power is reduced or even eliminated, thereby increasing the energy harvesting power.

Description

Technical Field

[0001] The present invention relates to a method for obtaining energy from an overhead ground wire by magnetic induction, so as to meet the power demand of online monitoring equipment for overhead lines installed on towers and facilitate the construction of digital transmission lines. Background Art

[0002] Online monitoring technology is a crucial tool for ensuring the safe and stable operation of overhead power lines. However, existing online power supply technology for overhead lines cannot adequately meet the actual power needs of monitoring equipment, limiting its development. For example, solar panels have insufficient output power during prolonged rainy or snow-covered conditions; current transformers installed on conductors are located on the high-voltage side and therefore cannot power equipment mounted on towers; wireless power transmission is inefficient and equipment costs are high; and new power generation technologies such as triboelectric and thermoelectric power generation have low power levels and immature technical systems.

[0003] Domestic overhead lines with voltage levels of 110kV and above are typically equipped with two ground wires for lightning protection. The power-frequency current in the AC overhead line conductors generates a power-frequency magnetic field in space, which acts on the ground wire loop to induce voltage or current. The ground wire has abundant magnetic induction energy, making it an ideal power source for online monitoring equipment.

[0004] Currently, energy harvesting is typically achieved by connecting the energy harvesting load in parallel across the insulators of a segmented, insulated ground wire to utilize ground wire magnetic induction energy. However, the ground wire's self-inductance and the mutual inductance between the two ground wires increase the reactive component in the energy harvesting circuit, limiting the full utilization of the ground wire's magnetic induction energy. Furthermore, for overvoltage protection, a decoupling inductor is often connected in series with the load to limit the rate of change of transient current. This inductance also consumes energy under normal operating conditions. Summary of the Invention

[0005] The purpose of the present invention is to provide an overhead ground wire magnetic induction energy harvesting device based on capacitor compensation, which reduces or even eliminates the influence of inductance on energy harvesting power by introducing a compensation capacitor into the ground wire energy harvesting device, thereby improving the energy harvesting power.

[0006] To this end, the present invention provides an overhead ground wire magnetic induction energy harvesting device based on capacitor compensation, which is used for drawing power from online monitoring equipment of overhead lines. The overhead line includes an ordinary ground wire and an OPGW ground wire, and its wiring method is: the ordinary ground wire is segmented and single-point grounded, and the OPGW ground wire is grounded tower by tower; the energy harvesting device draws power from the parallel gap of the ground wire insulator, including a decoupling inductor, a varistor, and a rectifier and voltage-stabilizing module, wherein the decoupling inductor and the varistor are connected in series to form an overvoltage protection module and are connected in parallel with the parallel gap; and also includes a compensation capacitor, which is connected in series with the rectifier and voltage-stabilizing module and then in parallel with the varistor. The rectifier and voltage-stabilizing module is used to output a DC voltage with a stable amplitude, and the compensation capacitor is used to increase the theoretical maximum power of energy harvesting.

[0007] The present invention realizes online power extraction of overhead ground wires based on the magnetic induction voltage generated on the ground wire by the mutual inductance coupling of the ground wires. By introducing a compensation capacitor in the energy extraction device, the influence of the ground wire loop inductance on the energy extraction power is reduced, thereby improving the energy extraction power. This device can meet the power demand of the overhead line online monitoring equipment installed on the tower, and assist in the construction of digital transmission lines.

[0008] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0010] Figure 1 It is a schematic diagram of the overhead line ground wire wiring structure;

[0011] Figure 2 A circuit diagram of the overhead ground wire magnetic induction energy harvesting device based on capacitance compensation according to the present invention is shown;

[0012] Figure 3 The ground wire energy equivalent circuit of the present invention is shown;

[0013] Figure 4 The structure of a 500kV single-circuit line is shown;

[0014] Figure 5 The structure of a 500kV double-circuit line is shown;

[0015] Figure 6 The structure of a 220kV single-circuit line is shown;

[0016] Figure 7 The structure of a 220kV double-circuit line is shown;

[0017] Figure 8 The structure of a 110kV single-circuit line is shown;

[0018] Figure 9 The structure of a 110kV double-circuit line is shown. DETAILED DESCRIPTION

[0019] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0020] The present invention realizes online power extraction of overhead ground wires based on the magnetic induction voltage generated on the ground wire by the mutual inductance coupling of the ground wires. By introducing a compensation capacitor in the energy extraction device, the influence of the ground wire loop inductance on the energy extraction power is reduced. Based on the ground wire energy extraction equivalent circuit, a method for selecting the optimal compensation capacitor value is proposed, thereby improving the theoretical maximum power of the overhead ground wire magnetic induction energy extraction.

[0021] The ground wire connection method of the overhead line used in the present invention is as follows Figure 1 As shown in the figure, overhead lines have two ground wires: a standard ground wire and an OPGW ground wire (i.e., a composite optical cable ground wire). The OPGW ground wire is grounded tower by tower. Standard ground wires are segmentally insulated and grounded at a single point. The ground wire insulators at the tension towers are horizontal. Several straight towers are arranged between adjacent tension towers. Only one straight tower has a standard ground wire that is grounded at a single point. The ground wires at the other straight towers are connected to the tower pole after passing through the insulators.

[0022] According to the idea of ​​capacitor compensation, the ground wire magnetic induction energy harvesting circuit proposed in this invention is designed as follows Figure 2 shown.

[0023] The energy taking device takes power from the parallel gap of the ground wire insulator, and includes a decoupling inductor, a varistor, a compensation capacitor, and a rectifier and voltage stabilization module.

[0024] The parallel gap is a built-in accessory of the ground wire insulator and serves to dissipate lightning current. The decoupling inductor and varistor together form the energy harvesting device's overvoltage protection module, connected in parallel with the parallel gap to prevent damage from lightning strikes. The compensation capacitor, connected in series with the rectifier and voltage regulator module and then in parallel with the varistor, increases the theoretical maximum power of the energy harvesting device. The rectifier and voltage regulator module converts the AC voltage into a stable DC voltage for the load.

[0025] The optimal compensation capacitor value can be obtained based on the ground wire energy equivalent circuit ( Figure 3 ) is obtained using the port Thevenin equivalent method. Assume that the energy extraction circuit is the loop formed by the ground wire between towers i and m, and the energy extraction load is installed on tower m. The OPGW ground wire is denoted by 1, and the segmented insulated ground wire is denoted by 2. l1: The loop formed by the OPGW and the ground; l2: The loop formed by the two ground wires.

[0026] Figure 2 The subscripts i and m in the column represent the tower number. The i-th column (between the i-1th tower and the i-th tower) and Z i-1(1) 、 They represent the self-impedance and eddy-induced potential of the OPGW in this gear respectively. Corresponding to the eddy induced potential between the two ground wires at node i and node m. i-m(1e) , Z i-m(2e) Respectively represent the self-impedance of the two ground wires between node i and node m. i It represents the tower grounding resistance, and Z1 represents the energy load.

[0027] For the part to the left of node i, let the equivalent voltage looking left from node i be The equivalent impedance is Z i(e) It is assumed that the induced potential of each OPGW ground wire is The self-impedance value is Z0, and the grounding resistance value of the tower is R0. Then we can deduce:

[0028]

[0029] According to formula (1), an iterative calculation can be formed, and the solution is carried out from point i to the left. When the number of towers on the left side of node i is large enough, in order to simplify the calculation, it can be approximately considered that Z i(e) ≈Z i-1(e) So we have:

[0030]

[0031] For the part to the right of node m, let the equivalent voltage looking from node m to the right be The equivalent impedance is Z m(e) It is assumed that the induced potential of each OPGW ground wire is The self-impedance value is Z0 ′ , the grounding resistance value of the tower is R0 ′ . Then we can deduce that:

[0032]

[0033] According to the above formula, an iterative calculation can be formed, and the solution is carried out from point m to the right. When the number of towers on the right side of node m is large enough, in order to simplify the calculation, it can be approximately considered that So we have:

[0034]

[0035] For the portion between nodes i and m, when performing equivalent circuit analysis, since the tower grounding resistance is much greater than the ground line impedance, the current flowing into the tower in the vertical direction can be ignored and the ground channel can be considered as an open circuit. Therefore, we have:

[0036]

[0037] In the formula is the average value of the induced potential of each level on the segmented insulated ground wire, Z 0(2) is the average self-impedance of each level of the segmented insulated ground wire. From this, the ground wire current when no load is connected can be calculated.

[0038]

[0039] On this basis, the Thevenin equivalent voltage from the energy-drawing load to the line can be obtained: With impedance Z e1 :

[0040]

[0041] The Thevenin equivalent impedance Z of the ground port calculated in formula (7) e1 is a complex number. The real part of the complex number represents the resistance of the ground loop, which cannot be compensated. The imaginary part of the complex number represents the inductive reactance of the ground loop, which can be compensated by a capacitor. Let the imaginary part of the equivalent impedance be X, and let the decoupling inductance used for overvoltage protection be L. Then the value of the compensation capacitor C can be determined according to formula (8):

[0042]

[0043] Where ω=2πf, f is the frequency of the wire current, which is 50Hz in China.

[0044] against Figures 4 to 9 The improvement in theoretical maximum ground-wire magnetic induction power extraction using the capacitor compensation method of the present invention was calculated for line structures of different voltage levels, as shown in Table 1. The results demonstrate that the present invention can effectively increase ground-wire magnetic induction power extraction, providing better power for online monitoring equipment for overhead lines.

[0045] Table 1. Energy efficiency improvement effect

[0046] Voltage level and line structure Energy extraction power improvement 110kV single circuit 20％ 110kV double circuit 22％ 220kV single circuit 19％ 220kV double circuit 24％ 500kV single circuit 23％ 500kV double circuit 22％

[0047] The foregoing description is merely an embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An overhead ground wire magnetic induction energy harvesting device based on capacitance compensation, used for harvesting power from online monitoring equipment of overhead lines, characterized in that: The overhead line includes a common ground wire and an OPGW ground wire, and the connection method is: the common ground wire is segmented and insulated and single-point grounded, and the OPGW ground wire is grounded tower by tower; The energy taking device takes power from the parallel gap of the ground wire insulator, and includes a decoupling inductor, a varistor, and a rectifier and voltage stabilization module, wherein the decoupling inductor and the varistor are connected in series to form an overvoltage protection module and are connected in parallel with the parallel gap; It also includes a compensation capacitor, which is connected in series with the rectifier and voltage regulator module and then in parallel with the varistor. The rectifier and voltage regulator module is used to output a DC voltage with a stable amplitude. The compensation capacitor is used to increase the theoretical maximum power of energy extraction. The calculation formula for the optimal capacitance value of the compensation capacitor is: ， Wherein, L is the decoupling inductance value, , is the conductor current frequency, X is the imaginary part of the Thevenin equivalent impedance of the ground port, where the Thevenin equivalent impedance of the ground port is a complex number. The calculation formula of the Thevenin equivalent impedance of the ground port is: ， Here, the energy-taking circuit of the ground wire is the circuit formed by the ground wire between the i-th tower and the m-th tower, and the energy-taking load is installed on the tower numbered m. 、 Respectively represent the self-impedance of the two ground wires between nodes i and m, is the equivalent impedance looking left from node i, is the equivalent impedance viewed from node m to the right.

2. The overhead ground wire magnetic induction energy harvesting device based on capacitance compensation according to claim 1, characterized in that: The equivalent impedance looking left from node i The calculation formula is as follows: ， ， in, is the average self-impedance of each OPGW ground wire, is the average grounding resistance of the tower.

3. The equivalent impedance of the overhead ground wire magnetic induction energy harvesting device based on capacitance compensation according to claim 1, viewed from the node m to the right The calculation formula is as follows: ， ， in, is the average self-impedance of each OPGW ground wire, is the average grounding resistance of the tower.

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