Non-intrusive high-voltage direct-current transmission line harmonic magnetic field energy collection device

Abstract

The invention provides a non-intrusive high-voltage direct-current transmission line harmonic magnetic field energy collection device. The device comprises an arc-shaped magnetic core and a magnetic flux collector, the arc-shaped magnetic core is located in the center of the device, the magnetic flux collectors are located at the two ends of the arc-shaped magnetic core, and the device can be placed near a power transmission line without being buckled on the power transmission line. The designed arc-shaped magnetic core is a non-closed arc-shaped magnetic core, the effective magnetic conductivity is low, and magnetic core saturation caused by strong direct current can be effectively avoided. When the magnetic core is not saturated, the alternating magnetic field generated by the harmonic current generates induced voltage in the coil based on electromagnetic induction, and then energy is collected. The magnetic core can be effectively prevented from being saturated by strong direct current, and the harmonic magnetic field energy collection capacity is guaranteed; and an alternating magnetic field generated by the harmonic current generates induced voltage in the coil based on an electromagnetic induction principle and outputs power to a load, and the process is not influenced by weather conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-voltage cable power transmission, and in particular relates to a non-invasive high-voltage direct current transmission line harmonic magnetic field energy collection device. Background Art

[0002] Due to the lack of abundant alternating electric and magnetic fields in high-voltage direct current (HVDC) transmission lines, the traditional magnetic field and electric field energy collection technology widely used in AC transmission lines is no longer applicable. Solar and wind energy collectors are affected by weather conditions and their output power is unstable. Therefore, there is always a lack of efficient and stable energy collection methods in HVDC transmission lines, which hinders the deployment of self-powered sensors in HVDC transmission lines. In the rectification and inversion links of the HVDC transmission system, the limited switching frequency of electronic switching devices leads to the coexistence of DC and harmonic currents in HVDC transmission lines. Summary of the invention

[0003] In order to solve the above problems, the present disclosure proposes for the first time a new method for collecting harmonic magnetic field energy of high-voltage direct current transmission lines by using a non-invasive high-voltage direct current transmission line harmonic magnetic field energy collection device. Traditional magnetic energy collectors based on current transformers will experience deep saturation of the magnetic core due to strong direct current in high-voltage direct current transmission lines, and will not be able to collect the magnetic field energy of harmonic currents. The arc-shaped magnetic core designed in the present disclosure has a low effective magnetic permeability because the magnetic core is non-closed, which can effectively avoid the saturation of the magnetic core caused by strong direct current. When the magnetic core is not saturated, the alternating magnetic field generated by the harmonic current will generate an induced voltage in the coil based on electromagnetic induction and then collect energy.

[0004] The technical solution adopted by the present disclosure to solve its technical problems is:

[0005] A non-intrusive high-voltage direct current transmission line harmonic magnetic field energy collection device, the device comprising: an arc-shaped magnetic core, a magnetic flux collector;

[0006] The arc-shaped magnetic core is located at the center of the device, and the magnetic flux collectors are located at both ends of the arc-shaped magnetic core.

[0007] Preferably, the arc-shaped magnetic core is a non-closed arc-shaped magnetic core.

[0008] Preferably, the effective magnetic permeability of the non-closed arc-shaped magnetic core is much lower than the effective magnetic permeability of the closed annular magnetic core.

[0009] Preferably, the device collects AC harmonic magnetic field energy in the high-voltage direct current transmission line based on the principle of electromagnetic induction.

[0010] Preferably, the method based on the device comprises the following steps: the external DC magnetic field strength generated by the DC current in the high-voltage DC transmission line is recorded as H e,dcThe effective value of the external alternating magnetic field intensity generated by the harmonic current is recorded as H e,ac ;

[0011] H can be obtained by calculating the following formula e,dc , H e,ac :

[0012]

[0013] Among them I dc and I ac are the effective values ​​of the line DC current and harmonic current, r is the radius of the arc core, a p is the side length of the flux collector, and ρ represents the distance from the center of the cross section of the HVDC transmission line to any point on the flux collector.

[0014] Preferably, the device further comprises: a coil and a load resistor.

[0015] Preferably, the alternating magnetic field generated by the harmonic current generates an induced voltage in the coil based on the principle of electromagnetic induction and outputs power to the load resistor.

[0016] The technical advantages of the present disclosure are as follows:

[0017] 1. Compared with the traditional magnetic energy collector based on current transformer, the present invention can effectively prevent the magnetic core from being saturated by strong DC current, thus ensuring the harmonic magnetic field energy collection capability;

[0018] 2. The alternating magnetic field generated by the harmonic current generates an induced voltage in the coil based on the principle of electromagnetic induction and outputs power to the load. The energy collection process based on the principle of electromagnetic induction is not affected by weather conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A comparison diagram of two magnetic core structures of a magnetic field energy harvester based on a current transformer and a non-intrusive DC harmonic magnetic field energy harvester in one embodiment of the present disclosure;

[0021] Figure 2 is a cross-sectional view of a non-intrusive DC harmonic magnetic field energy harvesting device having an arc-shaped magnetic core in one embodiment of the present disclosure;

[0022] Figure 3 It is a schematic diagram of the internal magnetization state of the arc-shaped magnetic core under the combined action of direct current and harmonic current in one embodiment of the present disclosure;

[0023] Figure 4 is an equivalent circuit diagram of a non-intrusive DC harmonic magnetic energy harvesting device in one embodiment of the present disclosure;

[0024] Figure 5 It is a schematic diagram of the contents of different harmonic currents relative to the direct current in a converter station A in one embodiment of the present disclosure;

[0025] Figure 6 In one embodiment of the present disclosure, different DC currents I dc Next (corresponding to different I ac ), induced voltage waveforms of non-intrusive DC harmonic magnetic field energy harvesting devices with different magnetic core materials;

[0026] in, Figure 6 (a) is Permalloy; Figure 6 (b) is Mn-Zn ferrite;

[0027] Figure 7 In one embodiment of the present disclosure, different DC currents I dc Time (I ac =0.3% I dc ), with a manganese-zinc ferrite core (a c =1.6cm) of non-intrusive DC harmonic magnetic field energy harvesting device V oc , P L and B c,dc Schematic diagram. DETAILED DESCRIPTION

[0028] The following will refer to the attached Figures 1 to 7 Specific embodiments of the present disclosure are described in detail. Although specific embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0029] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present disclosure, but the description is based on the general principles of the specification and is not used to limit the scope of the present disclosure. The scope of protection of the present disclosure shall be determined by the attached claims.

[0030] To facilitate understanding of the embodiments of the present disclosure, further explanation will be given below using specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present disclosure.

[0031] The present disclosure provides a non-intrusive high-voltage direct current transmission line harmonic magnetic field energy collection device to collect magnetic field energy of harmonic current, wherein the device comprises:

[0032] Arc core, flux collector;

[0033] The arc-shaped magnetic core is located at the center of the device, and the magnetic flux collectors are located at both ends of the arc-shaped magnetic core.

[0034] Preferably, the arc-shaped magnetic core is a non-closed arc-shaped magnetic core.

[0035] Preferably, the effective magnetic permeability of the non-closed arc-shaped magnetic core is much lower than that of the closed annular magnetic core.

[0036] For the above embodiments, it should be noted that, compared with the traditional magnetic field energy harvester based on current transformer, the non-intrusive DC harmonic magnetic field energy harvester disclosed in the present disclosure can effectively avoid the magnetic core saturation caused by strong DC current. The comparison of the two magnetic core structures is as follows: Figure 1 As shown, where:

[0037] In the traditional solution, a magnetic field energy harvesting device based on a current transformer is used in the AC power transmission line, which adopts a closed ring magnetic core. Figure 1 As shown in b in the figure, b must be buckled and installed on the transmission line in an intrusive manner when in use, so b is an intrusive magnetic field energy collector. However, this is not suitable for high-voltage DC transmission lines because: the closed annular magnetic core has a high effective magnetic permeability. When it is applied to high-voltage DC transmission lines, the strong DC magnetic field generated by the DC current will saturate the magnetic core and cannot generate an induced voltage in the coil.

[0038] Therefore, the present disclosure discloses a non-intrusive DC harmonic magnetic field energy harvesting device, which no longer uses a closed annular magnetic core, but instead uses an open, non-closed arc-shaped magnetic core. Figure 1 This non-closed arc-shaped magnetic core can be placed near the transmission line without intrusion and clipped on the transmission line, such as Figure 1 As shown in a in , a is a non-invasive magnetic field energy harvester.

[0039] Further, such as Figure 1As shown in a, a coil is arranged on the arc-shaped magnetic core, and two magnetic flux collectors are respectively connected to two ends of the arc-shaped magnetic core. Exemplarily, the end face of the arc-shaped magnetic core is a square, and the end faces of the two magnetic flux collectors are both square, and the side length thereof is greater than the side length of the arc-shaped magnetic core. (In order to reduce eddy current loss, commercial arc-shaped magnetic cores are usually stacked with multiple layers of thin plates, and the rectangular end faces are easy to produce. Therefore, in the present disclosure, the end faces of the arc-shaped magnetic cores are selected to be square. Note: It does not necessarily need to be a square. Rectangles with unequal lengths and widths are also acceptable, and irregular shapes are also acceptable. Here, a square is taken as an example. The end face shape of the flux collector should be consistent with the arc-shaped magnetic core, but larger in size. On the one hand, the larger size of the end face of the flux collector can collect more magnetic fields to increase the output power. On the other hand, the space between the size difference of the arc-shaped magnetic core and the end face of the flux collector is used to wind the coil, and the cross-section of the coil should not exceed the end face of the flux collector. Furthermore, the length and width should be proportionally larger than the end face of the magnetic core. In theory, the larger the length and width, the more magnetic fields are collected and the greater the output power. However, two points should also be considered: 1. The increase in length and width means that the size of the device has also become larger, so the output power is increased at the expense of increasing the volume; 2. In actual installation, the length and width are limited by the installation scenario. For example, in Figure 1 The length 1 of the side parallel to the transmission line can be appropriately larger, but the length 2 of the side perpendicular to the transmission line cannot be too large, otherwise it will touch the transmission line itself, which is not allowed. In general, the length and width can be as large as possible to increase the overall output power of the device, but the above two limitations must also be taken into account. )

[0040] It should be noted that in the present disclosure, since the arc-shaped magnetic core is a non-closed magnetic core, it will generate two opposite magnetic poles at its two ends after being magnetized in a magnetic field. These two magnetic poles will generate a demagnetization field inside the arc-shaped magnetic core in the opposite direction to the external magnetic field. The demagnetization field significantly reduces the magnetic induction intensity inside the arc-shaped magnetic core, thereby significantly reducing the effective magnetic permeability of the arc-shaped magnetic core. Therefore, the non-closed arc-shaped magnetic core has a strong anti-saturation ability.

[0041] When the magnetic field generated by the DC current does not saturate the magnetic core, the alternating magnetic field generated by the harmonic current in the magnetic core will generate an induced voltage in the coil based on the principle of electromagnetic induction and output power to the load. In other words, the magnetic flux density of the magnetic field generated by the DC current flowing through the transmission line under the action of the arc-shaped magnetic core should be less than the material saturation flux density of the arc-shaped magnetic core.

[0042] Furthermore, since the non-closed magnetic core will generate two opposite magnetic poles at its two ends after being magnetized in the magnetic field, these two magnetic poles will generate a demagnetization field inside the magnetic core in the opposite direction to the external magnetic field. The demagnetization field significantly reduces the magnetic field strength inside the magnetic core, so the effective magnetic permeability of the magnetic core is significantly reduced.

[0043] For example, the effective magnetic permeability of a non-closed arc-shaped magnetic core made of manganese-zinc ferrite material is usually 20-100 (related to the specific geometric parameters of the magnetic core, usually in the order of tens), while the effective magnetic permeability of a closed annular magnetic core made of manganese-zinc ferrite material is usually above 2000. In general, the effective magnetic permeability of a non-closed arc-shaped magnetic core is less than or equal to at least one twentieth of that of a closed annular magnetic core.

[0044] Figure 1 A cross section of a non-intrusive DC harmonic magnetic field energy harvesting device with a curved magnetic core is shown in Figure 2 It should be noted that the coil length should occupy as much space outside the core as possible to increase the load power. Figure 1 It is just a structural diagram. The analysis of the specific working principle is based on Figure 2 The detailed structure of the display is described.

[0045] The non-intrusive DC harmonic magnetic energy collection device disclosed in the present disclosure includes: a central arc-shaped magnetic core, magnetic flux collectors at both ends, a coil and a load resistor. Figure 1 The first load is the load resistor in the technical solution disclosed in the present invention, and the second load is the load resistor in the traditional solution.

[0046] In addition, the non-invasive DC harmonic magnetic energy collection device disclosed in the present disclosure collects AC harmonic magnetic field energy in high-voltage DC transmission lines based on the principle of electromagnetic induction.

[0047] See also Figure 2 , which shows a cross-sectional view of the non-invasive DC harmonic magnetic energy harvesting device disclosed by the present invention. The specific working principle is explained as follows:

[0048] set up a c , r and θ are the side length, radius and radian of the arc-shaped magnetic core respectively; a p and w are the side length and thickness of the flux collector, a coil is the coil height, H e,dc is the external DC magnetic field intensity generated by the DC current in the high-voltage DC transmission line, H e,ac It is the effective value of the external alternating magnetic field strength generated by the harmonic current in the high-voltage direct current transmission line. The external DC magnetic field generated by the DC current and the external alternating magnetic field generated by the harmonic current are superimposed to form a total magnetic field applied to the flux collector, and its instantaneous value is H e,dc +√2 H e,ac sin( ωt), ω is the angular frequency of the harmonic current.

[0049] H e,dc and H e,ac The calculation formula is:

[0050] (1)

[0051] (2)

[0052] in, I dc and I ac They are the effective values ​​of the line DC current and harmonic current, It represents the distance from the center of the cross section of the HVDC transmission line to any point on the flux collector. It should be noted that only the magnetic field collected by the flux collector can enter the arc core, so ρ The minimum and maximum values ​​of should be the minimum and maximum values ​​of the distance from any point on the end surface of the flux collector to the center of the cross section of the high-voltage DC transmission line, respectively, that is, ρ The value range is r - a p / 2 to r + a p / 2.

[0053] Furthermore, the current flowing through the high-voltage direct current transmission line includes two parts: a direct current component and a harmonic current component. The magnitude of the direct current and harmonic current flowing through the line is determined by the operating state of the power system itself, and has nothing to do with the arc-shaped magnetic core and coil in this device. This device is only used to collect the energy of the AC magnetic field generated by the harmonic current in the line, while avoiding the DC magnetic field generated by the DC current in the line from causing the magnetic core to saturate. Therefore, I dc and I ac It is determined by the operating state of the high-voltage DC transmission line itself and is not affected by the device of the present invention. I dc and I ac The magnitude of H determines the strength of the DC current magnetic field and the harmonic current magnetic field. e,dc and H e,ac , which in turn determines the DC bias point of the core in subsequent analysis B c,dc , Induction voltage V oc And the load power P L And other parameters.

[0054] The non-intrusive DC harmonic magnetic energy collection device disclosed in the present disclosure generates an induced voltage in a coil arranged at an arc-shaped magnetic core based on the principle of electromagnetic induction and outputs power to a load. Figure 1 As shown in a in , according to the principle of electromagnetic induction, the amplitude of the coil induced voltage depends on the rate of change of the magnetic induction intensity in the arc-shaped magnetic core. When the frequency of the harmonic current is constant, the higher its content, the greater the amplitude of the magnetic induction intensity generated inside the arc-shaped magnetic core, the greater the absolute value of the rate of change of the magnetic induction intensity, and the higher the coil induced voltage and load power. Similarly, when the harmonic current content is constant, the higher its frequency, the greater the absolute value of the rate of change of the magnetic induction intensity, and the higher the coil induced voltage and load power.

[0055] Specifically, the harmonic current content determines the magnetic field strength H it generates. e,ac From the following formula (9), we can know that the magnetic field strength H generated by the coil induced voltage and harmonic current is e,ac It is positively correlated with the magnetic field frequency f=(ω / 2π). The higher the coil induced voltage, the greater the load power.

[0056] Therefore, the harmonic magnetic field energy level is positively correlated with the content and frequency of the harmonic current. To simplify the analysis, the subsequent description and verification of the present disclosure will take the 12th harmonic current as an example.

[0057] See also Figure 3 , which shows the magnetization state inside the arc core under the combined action of DC current and harmonic current. The AC magnetic field generated by the harmonic current causes the magnetic field inside the core to be B c,dc The DC bias point is generated by the DC current. Due to the demagnetization field in the non-closed core, the DC magnetic field inside the core H c,dc Much lower than the external DC magnetic field H e,dc :

[0058] (3)

[0059] in, H d,dc is the DC demagnetization field, D M is the demagnetization coefficient, M dc is the DC magnetization intensity.

[0060] according to Figure 3 BH curve, when the device disclosed in the present disclosure is working, the arc core will work at the DC bias point B c,dc Nearby, where:

[0061] (4)

[0062] in, μ 0 is the vacuum permeability, μ e,dc is the DC effective permeability, B sat is the saturation flux density of the core material.

[0063] μ e,dc It can be calculated as:

[0064] μ e , dc = [ ( θ r + 2 w + a p − a c ) / θ r ] 1 / 3 ⋅ ( B c , dc / μ 0 H c , dc ) 1 + 1 . 7 4 d 3 m 1 . 87 ( ln 1 + d 1 − d − 2 d ) ( B c , dc μ 0 H c , dc − 1 ) (5)

[0065] in, m = (θr+ 2 w+a p -a c ) / a c , d = (1 -m -2 ) 1 / 2 .

[0066] in, B c,dc Must be less than the saturation flux density of the core material B sat , the present disclosure can use equations (1)(4)(5) to determine whether the magnetic core is in a saturated state.

[0067] Furthermore, by substituting equations (1) and (5) into equation (4), the DC bias point can be obtained: B c,dc ,like B c,dc < B sat , the core is not saturated, and an induced voltage will be generated in the coil under the action of the AC magnetic field generated by the harmonic current. Otherwise, the core is saturated and no induced voltage is generated in the coil. When an induced voltage is generated in the coil, the non-closed arc core is placed near the transmission line, and the distance range of the vicinity is determined as follows:

[0068] according to Figure 2 , the radius of the arc core is r, and its center coincides with the center of the transmission line cross section. The minimum distance between the flux collectors at both ends of the arc core and the center of the transmission line cross section is r - a p / 2, to ensure installation feasibility, this distance should be greater than the radius of the transmission line cross section.

[0069] The induced voltage of the coil is generated by the AC magnetic field generated by the harmonic current. The external AC magnetic field generated by the harmonic current√2 H e,ac sin( ωt ) The instantaneous value of the AC magnetic field generated inside the magnetic core is √2 H c,ac sin( ωt ),in H c,ac is the effective value of the AC magnetic field inside the core, and ω is the angular frequency of the harmonic current. The instantaneous value of the AC magnetic induction intensity generated by the AC magnetic field inside the core is √2 B c,ac sin( ωt ),in B c,ac It is the effective value of the AC magnetic induction intensity inside the magnetic core. B c,ac It can be calculated as:

[0070] (6)

[0071] The AC effective permeability μ e,ac It can be expressed as:

[0072] μ e , ac = [ ( θ r + 2 w + a p − a c ) / θ r ] 1 / 3 ⋅ μ d | H = H c , dc 1 + 1 . 7 4 d 3 m 1 . 87 ( ln 1 + d 1 − d − 2 d ) ( μ d | H = H c , dc − 1 ) (7)

[0073] in, μ d is the differential relative permeability of the core material. When the differential relative permeability of the core material is high, the effective permeability of the non-closed core is almost unaffected by the change in the differential relative permeability. Therefore, see Figure 1 , Figure 2 ,for Figure 1 The arc core shown in a, when the arc core is not saturated, μ e,ac Pressable μ e,dc Estimate:

[0074] μ e , dc ≈ μ e , ac ≈ [ ( θ r + 2 w + a p − a c ) / θ r ] 1 / 3 ⋅ μ i 1 + 1 . 7 4 d 3 m 1 . 87 ( ln 1 + d 1 − d − 2 d ) ( μ i − 1 ) (8)

[0075] in, μ i is the initial relative magnetic permeability of the core material. Figure 4 The equivalent circuit of the non-intrusive DC harmonic magnetic energy harvesting device is demonstrated. V oc is the effective value of the coil induced voltage, which can be expressed as:

[0076] (9)

[0077] Where ω is the angular frequency of the magnetic field, N is the number of turns of the coil, A core is the cross-sectional area of ​​the core. As mentioned above, it can be seen from equation (9) that the magnetic field strength H generated by the coil induced voltage and harmonic current is e,ac It is positively correlated with the magnetic field frequency f=(ω / 2π). The higher the coil induced voltage, the greater the load power. Therefore, the harmonic magnetic field energy level is positively correlated with the content and frequency of the harmonic current.

[0078] Figure 4 In the coil resistance R coil Including core loss resistance R core and wire resistance R wire The frequency of harmonic current in high-voltage DC transmission lines is mainly below 1kHz, and the alternating magnetic field generated is a low-frequency magnetic field. Under low-frequency conditions, the eddy current loss and hysteresis loss of the magnetic core can be ignored. Therefore, R coil Approximately equal to R wire .

[0079] Furthermore, in another embodiment,

[0080] The device also includes a compensation capacitor.

[0081] This is to improve the power transmission efficiency by forming a series resonance between the compensation capacitor and the coil inductance.

[0082] For ease of explanation, the compensation capacitor C p Coil Inductance L coil Forming series resonance to improve power transfer efficiency:

[0083] (10)

[0084] in, l coil is the coil length, N is the number of coil turns, A core is the cross-sectional area of ​​the core.

[0085] Depend on Figure 4 The equivalent circuit shown in the figure shows that when no compensation capacitor is added C p When the inductance of the coil is jωL coil Will increase the total circuit impedance, thereby reducing the load current iL and load power P L After introducing the compensation capacitor that forms series resonance with the coil inductance, its capacitive reactance is 1 / JωC p Inductive reactance with coil inductance JωL coil cancel each other out, the load current i L and load power P L Will increase.

[0086] Under impedance matching, that is, the load resistance R L Equal to the coil resistance R coil , load power P L It can be expressed as:

[0087] (11)

[0088] in, V oc is the effective value of the coil induced voltage.

[0089] When the HVDC transmission line is a transmission line of what level or parameter, for ±500kV HVDC transmission line,

[0090] The parameters of the non-intrusive HVDC transmission line harmonic magnetic field energy harvesting device are shown in Table I:

[0091] Table I Parameters of non-intrusive HVDC line harmonic magnetic field energy harvesting device

[0092]

[0093] Figure 5 The schematic diagram of the content of different harmonic currents relative to the DC current in converter station A is shown. Since the harmonic magnetic field energy level is positively correlated with the content and frequency of the harmonic current, considering the two factors of the content and frequency of the harmonic current, Figure 5 The 12th harmonic current has the highest magnetic field energy level. The effectiveness of the device disclosed in the present disclosure was experimentally verified using the 12th harmonic current as an example. Figure 5 The frequency of the harmonic current set in the experiment is 600Hz, and the effective value of the harmonic current is I ac Always the effective value of DC current I dc 0.3% of the total.

[0094] Figure 6 Shows different DC currentsI dc Next (corresponding to different I ac ), the induced voltage waveforms of the non-intrusive HVDC line harmonic magnetic field energy harvesting device with different magnetic core materials, where Figure 6 (a) is Permalloy, Figure 6 (b) is Mn-Zn ferrite. Permalloy and manganese-zinc ferrite are commonly used magnetic core materials. The induced voltage of the non-intrusive high-voltage direct current transmission line harmonic magnetic field energy harvesting device with permalloy core increases approximately linearly with the DC current, which is consistent with the theoretical analysis. However, when I dc When the current is 1000A, the induced voltage of the non-intrusive HVDC line harmonic magnetic field energy harvesting device with a manganese-zinc ferrite core is extremely low. This is mainly caused by the saturation of the core. I dc The estimated DC bias point is 1000A. B c,dc Close to the saturation flux density of manganese-zinc ferrite B sat (about 0.52T), so the effective magnetic permeability and induced voltage of the magnetic core are extremely small. B sat (about 0.75T) is higher than that of manganese-zinc ferrite, and the core is still in a non-saturated state.

[0095] Figure 7 For different DC currents I dc hour( I ac =0.3% I dc ), with a manganese-zinc ferrite core ( a c =1.6cm) non-intrusive HVDC transmission line harmonic magnetic field energy harvesting device V oc , P L and B c,dc As shown in the figure, increasing the cross-sectional area of ​​the magnetic core A core It can reduce its effective magnetic permeability and thus enhance the core's anti-saturation ability. a c From 0.8cm to 1.6cm, the other core geometric parameters remain unchanged. Figure 7 Observe that in I dc Core DC bias point at 1000A B c,dcOnly 0.2T ( B sat =0.52T). Since the magnetic core is not saturated, the induced voltage V oc and load power P L Always follow I dc And increase ( I ac =0.3% I dc ). The experimental results are in good agreement with the calculated results. I dc =1000A, I ac =3A / 600Hz, the designed non-intrusive HVDC transmission line harmonic magnetic field energy harvesting device achieved a load power of 25.79mW and a power efficiency of 0.279mW / cm 3 power density.

[0096] The above general description of the invention involved in this disclosure and the description of its specific implementation methods should not be understood as limiting the technical solutions of the invention. Based on the contents disclosed in this disclosure, those skilled in the art can, without violating the constituent elements of the invention involved, add, reduce or combine the disclosed technical features in the above general description or / and specific implementation methods (including examples) to form other technical solutions within the protection scope of this disclosure.

Claims

1. A non-intrusive high-voltage direct current transmission line harmonic magnetic field energy collection device, characterized in that: The device comprises: an arc-shaped magnetic core and a magnetic flux collector; The arc-shaped magnetic core is located at the center of the device, and the magnetic flux collectors are located at both ends of the arc-shaped magnetic core. The device can be placed near the transmission line without being clipped onto the transmission line.

2. The device according to claim 1, characterized in that Preferably, the arc-shaped magnetic core is a non-closed arc-shaped magnetic core.

3. The device according to claim 2, characterized in that The effective magnetic permeability of the non-closed arc-shaped magnetic core is much lower than the effective magnetic permeability of the closed ring-shaped magnetic core.

4. The device according to claim 1, characterized in that The device collects AC harmonic magnetic field energy in a high-voltage direct current transmission line based on the principle of electromagnetic induction.

5. The device according to claim 1, characterized in that The method based on the device comprises the following steps: recording the external DC magnetic field strength generated by the DC current in the high-voltage DC transmission line as H e,dc , the effective value of the external alternating magnetic field intensity generated by the harmonic current is recorded as H e,ac ; The following formula is used to calculate the H e,dc , H e,ac : ； ， in I dc and I ac are the effective values ​​of the line DC current and harmonic current respectively, r is the radius of the arc core, a p is the side length of the flux collector, and ρ represents the distance from the center of the cross section of the HVDC transmission line to any point on the flux collector.

6. The device according to claim 1, characterized in that The device also includes: a coil and a load resistor.

7. The device according to claim 6, characterized in that The alternating magnetic field generated by the harmonic current generates an induced voltage in the coil based on the principle of electromagnetic induction and outputs power to the load resistor.

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