A CT energy harvesting device for high-voltage transmission lines with wide current variations

Abstract

The present invention discloses a CT energy harvesting device for high-voltage transmission lines with wide current variations, comprising: an energy harvesting unit connected to a single-phase rectifier unit, the energy harvesting unit being used to provide electrical energy to the single-phase rectifier unit; the single-phase rectifier unit being connected to a filter energy storage unit, both of which are grounded; the filter energy storage unit being connected to an equivalent load RL; the single-phase rectifier unit rectifying the electrical energy; and the filter energy storage unit filtering the electrical energy and increasing the output power. The present invention harvests stable energy through a magnetic core when current in a high-voltage transmission line varies; and provides stable and sufficient energy to the load through rectification and filtering, thereby achieving the purpose of providing stable electrical energy for online monitoring equipment in a high-voltage transmission system.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic induction and relates to a CT energy acquisition device for high-voltage transmission lines with wide-range current changes. Background Art

[0002] As power systems become increasingly intelligent, high-voltage power transmission systems are often equipped with various wireless online monitoring devices to monitor the system's status in real time. However, the high-voltage environment of transmission lines makes designing a safe power supply for these monitoring devices a challenge.

[0003] In high-voltage environments, the power supply's safety, output stability, and anti-interference capabilities must all be given full consideration. Common methods for powering online equipment on high-voltage transmission lines include battery power, solar power, laser power, and current transformer power extraction. Battery power has the disadvantages of limited capacity, short battery life, and the need for regular replacement. Solar power has the disadvantages of low conversion efficiency, limited power, and significant weather susceptibility. Laser power extraction has the disadvantages of complex principles, difficulty in implementation, and high cost. Current transformer power extraction, on the other hand, utilizes electromagnetic induction to draw power from high-voltage transmission lines, offering high power draw and low cost. Because the power collected by a CT is proportional to the current in the transmission line, the power collected on the secondary side is positively correlated with the current in the high-voltage transmission line. Faults such as short circuits or grounding in the high-voltage transmission line can cause a sharp increase in current in the line, resulting in excessive energy drawn by the energy harvesting device, causing severe heating of the current transformer and even direct damage to the energy harvesting device.

[0004] To address the aforementioned issues with current transformer-based energy harvesting devices, scholars have conducted extensive research, proposing methods such as impedance matching, designing dedicated control circuits, and hybrid power supply. However, these methods also have significant drawbacks. Impedance matching is complex, difficult to implement, and requires extensive computational verification. Designing dedicated control circuits increases system complexity and cost. Hybrid power supply not only increases cost and complexity of the energy harvesting device, but also impacts system stability. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems in the prior art and provide a CT energy harvesting device for high-voltage transmission lines with a wide range of current changes. The device can collect stable energy through a saturable magnetic core when the current in the voltage transmission line changes; and provide stable and sufficient energy to the load through rectification and filtering processing, thereby achieving the purpose of providing stable electric energy for online monitoring equipment in the high-voltage transmission system.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A CT energy harvesting device for high-voltage transmission lines with wide current variations, comprising: an energy harvesting unit, a single-phase rectifier unit, a filter energy storage unit, and an equivalent load RL;

[0008] The energy collection unit is connected to the single-phase rectifier unit, and the energy collection unit is used to provide electric energy to the single-phase rectifier unit; the single-phase rectifier unit is connected to the filter energy storage unit, and the single-phase rectifier unit and the filter energy storage unit are grounded at the same time; the filter energy storage unit is connected to the equivalent load RL; the single-phase rectifier unit rectifies the electric energy; the filter energy storage unit filters the electric energy and increases the output power.

[0009] A further improvement of the present invention is:

[0010] The energy harvesting unit includes a magnetic core, a power transmission line, and a secondary winding;

[0011] The magnetic core is a ring; the power transmission line passes through the center of the magnetic core; the secondary winding is evenly wound on the surface of the magnetic core; the secondary winding is connected to the single-phase rectifier unit;

[0012] The magnetic core is an easily saturated magnetic core; the saturation magnetic induction intensity Bs of the magnetic core is ≤0.6T; the maximum relative magnetic permeability μmax is ≥1000000; the hysteresis loop squareness ratio Br / Bs is ≥0.9; the loss Ps of the magnetic core is ≤65W / kg under the conditions of a frequency of 50Hz and a magnetic induction intensity of 0.4T.

[0013] The energy collection unit is used to provide electrical energy to the single-phase rectifier unit. Specifically, current flows through the power transmission line, generating a changing magnetic field. The changing magnetic field excites an induced voltage in the secondary winding and inputs it into the single-phase rectifier unit.

[0014] The waveform of the induced voltage is a centrally symmetrical AC voltage; within half a cycle, the absolute value of the volt-second product of the induced voltage is a constant.

[0015] The secondary winding is a coil made by evenly wrapping enameled wire around the magnetic core.

[0016] The single-phase rectifier unit includes a diode D1, a diode D2, a diode D3 and a diode D4; the positive electrode of the diode D1 is respectively connected to the negative electrode of the diode D2 and one output end of the secondary winding, the positive electrode of the diode D2 is respectively connected to the positive electrode of the diode D4, the ground and the filter energy storage unit, the negative electrode of the diode D4 is respectively connected to the positive electrode of the diode D3 and the other output end of the secondary winding, and the negative electrode of the diode D3 is connected to the negative electrode of the diode D1 and the filter energy storage unit.

[0017] The filtering energy storage unit includes several capacitor groups Cf, output terminal P1-1 and output terminal P1-2;

[0018] Several capacitor groups Cf are connected in parallel, including: a first capacitor group Cf, a last capacitor group Cf and a middle capacitor group Cf;

[0019] One end of the first capacitor group Cf is respectively connected to the cathode of the diode D3 and one end of the adjacent middle capacitor group Cf, and the other end of the first capacitor group Cf is respectively connected to the anode of the diode D4 and the other end of the adjacent middle capacitor group Cf; one end of the last capacitor group Cf is respectively connected to the output terminal P1-1 and one end of the previous capacitor group Cf; the other end of the last capacitor group Cf is connected to the output terminal P1-2 and the other end of the previous capacitor group Cf; the output terminal P1-1 and the output terminal P1-2 are connected to the equivalent load RL.

[0020] Diode D1 , diode D2 , diode D3 , and diode D4 are all Schottky diodes.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention utilizes the constant volt-second product of the secondary winding voltage when using a saturable magnetic core as a CT. By sequentially cascading an energy harvesting unit, a single-phase rectifier, a filter energy storage unit, and an equivalent load (RL), the energy harvesting unit provides electrical energy, which then flows through the single-phase rectifier and filter energy storage units, which then rectify and filter the energy, increasing the output power. Finally, the energy is delivered to the equivalent load (RL). This invention can provide stable power for online monitoring equipment in high-voltage transmission systems.

[0023] Furthermore, the current flowing through the power transmission line generates a changing magnetic field, which excites an induced voltage in the secondary winding and inputs it into the single-phase rectifier unit, thereby effectively providing a stable voltage.

[0024] The present invention has simple design, stable output and strong surge current resistance capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a schematic diagram of a CT energy extraction device for high-voltage transmission lines with a wide range of current changes according to the present invention;

[0027] Figure 2 is the hysteresis loop of the easily saturated magnetic core.

[0028] Among them, 1-energy collection unit, 2-single-phase rectifier unit, 3-filter energy storage unit, 4-magnetic core, 5-secondary winding, 6-power transmission line. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0031] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0032] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0034] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0035] The present invention is described in further detail below with reference to the accompanying drawings:

[0036] See also Figure 1 The present invention discloses a CT energy harvesting device for high-voltage transmission lines with a wide range of current changes, comprising: an energy harvesting unit 1, a single-phase rectifier unit 2, a filter energy storage unit 3 and an equivalent load RL;

[0037] Energy harvesting unit 1 is connected to a single-phase rectifier unit 2 and supplies electrical energy to the unit. The unit is also connected to a filter energy storage unit 3, both of which are grounded. The filter energy storage unit 3 is connected to an equivalent load RL. The unit 2 rectifies the electrical energy, while the filter energy storage unit 3 filters the energy and increases the output power. Energy harvesting unit 1 comprises a magnetic core 4, a power transmission line 6, and a secondary winding 5. The magnetic core 4 is a ring; the power transmission line 6 passes through the center of the core 4; the secondary winding 5 is evenly wound around the surface of the core 4; and the secondary winding 5 is connected to the single-phase rectifier unit 2. Energy harvesting unit 1 supplies electrical energy to the unit 2 by: Current flowing through the power transmission line 6 generates a varying magnetic field, which induces an induced voltage in the secondary winding 5, which is then fed into the unit 2. The induced voltage waveform is a centrally symmetrical AC voltage; within each half cycle, the absolute value of the volt-second product of the induced voltage is constant. The secondary winding 5 is a coil formed by uniformly winding an enameled wire around the magnetic core 4 .

[0038] Magnetic core 4 is a saturable core. This core has a high magnetic permeability, allowing it to maintain high magnetic conductivity when unsaturated, generating a sufficiently large induced electromotive force. The saturation magnetic flux density (Bs) of core 4 is ≤ 0.6 T; the maximum relative magnetic permeability (μmax) is ≥ 1,000,000; the hysteresis loop squareness ratio (Br / Bs) is ≥ 0.9; and the loss (Ps) of core 4 is ≤ 65 W / kg at a frequency of 50 Hz and a magnetic flux density of 0.4 T.

[0039] This magnetic material has a very low coercive force Hr and saturation magnetic flux density Bs, and its hysteresis loop is a very small rectangle. Therefore, its hysteresis loss is very low. When this magnetic material is used as a magnetic core, the induced voltage generated by the secondary winding 5 has a constant absolute value of the volt-second product.

[0040] The single-phase rectifier unit 2 includes a diode D1, a diode D2, a diode D3 and a diode D4; the positive electrode of the diode D1 is respectively connected to the negative electrode of the diode D2 and one output end of the secondary winding 5, the positive electrode of the diode D2 is respectively connected to the positive electrode of the diode D4, the ground and the filter energy storage unit 3, the negative electrode of the diode D4 is respectively connected to the positive electrode of the diode D3 and the other output end of the secondary winding 5, and the negative electrode of the diode D3 is connected to the negative electrode of the diode D1 and the filter energy storage unit 3.

[0041] The filtering energy storage unit 3 includes several capacitor groups Cf, an output terminal P1-1 and an output terminal P1-2;

[0042] Several capacitor groups Cf are connected in parallel, including: a first capacitor group Cf, a last capacitor group Cf and a middle capacitor group Cf;

[0043] One end of the first capacitor group Cf is respectively connected to the cathode of the diode D3 and one end of the adjacent middle capacitor group Cf, and the other end of the first capacitor group Cf is respectively connected to the anode of the diode D4 and the other end of the adjacent middle capacitor group Cf; one end of the last capacitor group Cf is respectively connected to the output terminal P1-1 and one end of the previous capacitor group Cf; the other end of the last capacitor group Cf is connected to the output terminal P1-2 and the other end of the previous capacitor group Cf; the output terminal P1-1 and the output terminal P1-2 are connected to the equivalent load RL.

[0044] Diode D1 , diode D2 , diode D3 , and diode D4 are all Schottky diodes.

[0045] See also Figure 2 The principle of the constant value of the volt-second product proposed by the present invention is described as follows: In the hysteresis loop, the saturation magnetic induction intensity at point b is expressed as B s , and its corresponding saturation magnetic field strength is H s Point a in the figure represents the residual magnetism B r , the coercive force is H r .

[0046] where i p (t) represents the current in the high-voltage power transmission line. When i p (t) increases from zero to i t1 When the magnetization point on the hysteresis loop moves from point a' on the curve to point b. In this process, the magnetic induction intensity B changes from B to r Change to B s At this time, the secondary winding of the energy harvesting unit generates an induced electromotive force v s (t). When i p (t) continues to increase to i p-pk When the value is , the magnetization curve moves from point b to point c. In this process, the core is always in saturation state, and the change of magnetic flux density from point b to point c is zero. According to the principle of electromagnetic induction, the secondary winding of the energy harvesting unit at this time almost does not generate induced electromotive force, so it can be considered that v s (t) is zero. When the current i in the power transmission line p (t) After entering the negative half cycle, the principle is the same and the process is similar. The v generated in this stage s (t) The voltage is negative. Figure 1 The shaded area in the figure represents the voltage generated in the CT secondary winding. s(t) time period.

[0047] Furthermore, according to Ampere's circuit theorem, the magnetic field strength H is: H = k·i p , where k is determined by the number of turns of the secondary winding on the magnetic ring in the energy harvesting unit and the effective magnetic path length of the magnetic core. s When p Reaching saturation current i t1 When the saturated material is determined, H s is a fixed value, i t1 is also a fixed value. Figure 1 As shown, regardless of p How does the value of (t) change, the current i t1 Therefore, based on the experimental data, we can analyze that the saturation time is t1.

[0048] i p (t) is represented by i p (t) = i p-pk ·sin(2πf·t), f is the voltage frequency. When the current value is i t1 When , the corresponding time t1 can be expressed as formula (1):

[0049]

[0050] From the above formula (1), it can be concluded that t1 increases with i p (t) decreases with the increase of

[0051] According to the law of electromagnetic induction, the induced voltage in the coil of the energy harvesting unit can be expressed as formula (2):

[0052] v s (t)=-N·ΔB·S / Δt (2)

[0053] For the easily saturated core, Δt in formula (2) is the non-saturated operating time. Figure 1 ΔB is a fixed value based on the core material. Figure 1 Indicated as 2B s N is the number of turns of the secondary winding, and S is the cross-sectional area of ​​the core, which is a constant when the core size is determined.

[0054] The aforementioned volt-second product is Λ, then we have formula (3):

[0055] Λ=v s (t)·Δt=-N·2B s ·S (3)

[0056] According to the above content, once the magnetic core 4 is determined, the parameters on the right side of the equation (3) are all known constants. Therefore, the value of the volt-second product Λ is also fixed. In addition, let T be the current i p (t) period, the average voltage U output by the CT secondary winding o =2Λ / T, which is also a fixed value and is not affected by the current i in the transmission line. p The influence of (t) can be expressed as:

[0057]

[0058] The present invention comprises an energy collection unit 1, a single-phase rectification unit 2 and a filtering energy storage unit 3 which are cascaded in sequence.

[0059] Specifically, the output line of the secondary winding 5 in the energy harvesting unit 1 is a connection terminal connected to the lower-level unit; the AC side of the rectifier bridge in the single-phase rectifier unit 2 is connected to two terminals, which are connected to the secondary winding 5 of the CT in the energy harvesting unit 1; similarly, the DC side has two connection terminals for connecting to the filter energy storage unit 3.

[0060] Capacitor group C of filter energy storage unit 3 f There are two terminals on each side. The two terminals on the left are the front connection terminals for the cascade connection between the unit and the single-phase rectifier unit 2; the two terminals on the right are the output terminals P 1-1 and P 1-2 , used to connect the equivalent load RL. This embodiment finally passes P 1-1 and P 1-2 Output energy to the load.

[0061] Since the current i in the high-voltage power transmission line p (t) is the industrial frequency AC current, so when the current i p (t) The saturation current I of the core has not been reached s When the secondary winding of CT in the energy collection unit generates a corresponding induced electromotive force, which is rectified by the single-phase rectifier unit and then transmitted to the capacitor group C f and equivalent load RL; when i p When (t) increases to a certain value, the magnetic field generated by it causes the core to saturate. At this point, the secondary winding of the CT no longer generates induced electromotive force, and the CT no longer extracts energy from the high-voltage power transmission line. Therefore, the capacitor group C at this time f Provide energy to equivalent load RL alone.

[0062] The specific working steps of this embodiment are as follows:

[0063] 1. Pass the power transmission line through the magnetic ring in the energy harvesting unit.

[0064] 2. The current in the power transmission line excites a magnetic field in the magnetic ring of the energy harvesting unit. When the instantaneous value of the current in the power transmission line is less than the saturation current of the magnetic core, the magnetic core of the CT operates in a non-saturated state mode, and an induced electromotive force of Δt duration is induced in the secondary winding.

[0065] 3. The induced electromotive force described in step 2 is converted into a DC pulse voltage v through a single-phase rectifier unit s (t).

[0066] 4. When the DC pulse voltage v s (t) is less than the capacitor group C in the filter energy storage unit f When the voltage is on, the energy induced by this part is equal to the capacitance group C f The released energy supplies power to the load.

[0067] 5. When the DC pulse voltage in step 3 is greater than the capacitor group C f When the voltage is on, the energy collected by the energy collection unit is the capacitor group C f On the other hand, it charges the equivalent load RL.

[0068] 6. When the CT magnetic ring in the energy harvesting unit 1 operates in a saturated state, that is, the current in the power transmission line is greater than the saturation current, the induced electromotive force induced by the secondary winding 5 is so small that it can be ignored.

[0069] 7. The induced electromotive force described in step 6 is too small to pass through the single-phase rectifier unit. Therefore, this part of the energy will not be transferred to the capacitor bank C f This will not affect the conclusion that the volt-second product is a constant. That is, the average voltage U output by the secondary winding is o It will not change, and the stability of the collected energy will not be affected.

[0070] 8. When the magnetic ring of CT in the energy collection unit works in saturation mode, the capacitor group C in the filter energy storage unit f The released electrical energy is used to supply power to the equivalent load RL alone.

[0071] 9. In the power supply process in step 8, due to the energy storage capacitor group C f The capacitance is large enough and the electric energy is sufficient, so there will be no voltage U o Dropped to 0.

[0072] 10. For the embodiment of the present invention, the CT is in a discontinuous energy-taking state, but due to the existence of the single-phase rectifier unit and the filter energy storage unit, the voltage U output on the transmission terminal is o It is a continuous DC voltage with very small ripple.

[0073] It is particularly noteworthy that in the process of steps 2 to 8, as long as the magnetic field generated by the current of the high-voltage power transmission line exists within one cycle at a moment that can cause the saturable magnetic core to enter a saturated state, the voltage volt-second product generated by the aforementioned secondary winding is a constant.

[0074] The present invention utilizes the saturable characteristic of saturable magnetic materials to enable the CT in the energy harvesting unit to operate in an intermittent energy harvesting mode, thereby increasing the current applicable range of the energy harvesting device; utilizes the small hysteresis loop area and low iron loss characteristics of the saturable magnetic core to increase the thermal stability of the CT energy harvesting device; utilizes the constant volt-second product characteristic to improve the output stability and surge current resistance of the energy harvesting device; finally, a single-phase rectifier unit and a filter energy storage unit are designed to increase the output power.

[0075] The above are merely preferred embodiments of the present invention and are 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, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A CT energy extraction device for high-voltage transmission lines with wide current variations, characterized in that: include: Energy collection unit (1), single-phase rectifier unit (2), filter energy storage unit (3) and equivalent load RL; The energy collection unit (1) is connected to a single-phase rectifier unit (2), and the energy collection unit (1) is used to provide electric energy to the single-phase rectifier unit (2); the single-phase rectifier unit (2) is connected to a filter energy storage unit (3), and the single-phase rectifier unit (2) and the filter energy storage unit (3) are grounded at the same time; the filter energy storage unit (3) is connected to an equivalent load RL; the single-phase rectifier unit (2) rectifies the electric energy; the filter energy storage unit (3) filters the electric energy and increases the output power; the energy collection unit (1) comprises a magnetic core (4), a power transmission line (6), and a secondary winding (5); The magnetic core (4) is a ring; the power transmission line (6) passes through the center of the magnetic core (4); the secondary winding (5) is evenly wound on the surface of the magnetic core (4); the secondary winding (5) is connected to the single-phase rectifier unit (2); The magnetic core (4) is an easily saturated magnetic core; the saturation magnetic induction intensity Bs of the magnetic core (4) is ≤0.6T; the maximum relative magnetic permeability μmax is ≥1000000; the hysteresis loop squareness ratio Br / Bs is ≥0.9; and the loss Ps of the magnetic core (4) is ≤65W / kg under the conditions of a frequency of 50Hz and a magnetic induction intensity of 0.4T.

2. The CT energy extraction device for high-voltage transmission lines with wide current variation according to claim 1, characterized in that: The energy collection unit (1) is used to provide electric energy to the single-phase rectifier unit (2), specifically: current flows through the power transmission line (6), generating a changing magnetic field, and the changing magnetic field excites an induced voltage in the secondary winding (5) and inputs it to the single-phase rectifier unit (2).

3. The CT energy extraction device for high-voltage transmission lines with wide current variation according to claim 2, characterized in that: The waveform of the induced voltage is a centrally symmetrical AC voltage; within a half cycle, the absolute value of the volt-second product of the induced voltage is a constant value.

4. The CT energy extraction device for high-voltage transmission lines with wide current variation according to claim 3, characterized in that: The secondary winding (5) is a coil obtained by uniformly winding an enameled wire around a magnetic core (4).

5. The CT energy extraction device for high-voltage transmission lines with wide current variation according to claim 4, characterized in that: The single-phase rectifier unit (2) comprises a diode D1, a diode D2, a diode D3 and a diode D4; the positive electrode of the diode D1 is respectively connected to the negative electrode of the diode D2 and one output end of the secondary winding (5); the positive electrode of the diode D2 is respectively connected to the positive electrode of the diode D4, the ground and the filter energy storage unit (3); the negative electrode of the diode D4 is respectively connected to the positive electrode of the diode D3 and the other output end of the secondary winding (5); and the negative electrode of the diode D3 is connected to the negative electrode of the diode D1 and the filter energy storage unit (3).

6. The CT energy extraction device for high-voltage transmission lines with wide current variation according to claim 5, characterized in that: The filtering energy storage unit (3) comprises a plurality of capacitor groups Cf, an output terminal P1-1 and an output terminal P1-2; The plurality of capacitor groups Cf are connected in parallel to each other, including: a first capacitor group Cf, a last capacitor group Cf and a middle capacitor group Cf; One end of the first capacitor group Cf is respectively connected to the cathode of the diode D3 and one end of the adjacent middle capacitor group Cf, and the other end of the first capacitor group Cf is connected to the anode of the diode D4 and the other end of the adjacent middle capacitor group Cf; one end of the last capacitor group Cf is respectively connected to the output terminal P1-1 and one end of the previous capacitor group Cf; the other end of the last capacitor group Cf is connected to the output terminal P1-2 and the other end of the previous capacitor group Cf; the output terminal P1-1 and the output terminal P1-2 are connected to the equivalent load RL.

7. The CT energy extraction device for high-voltage transmission lines with wide current variation according to claim 6, characterized in that: The diode D1 , the diode D2 , the diode D3 and the diode D4 are all Schottky diodes.

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