Air gap commutating device

Abstract

The application discloses an air gap commutation device, a controller is used to obtain a first parameter related to a fault current in a direct current power grid, and a target air gap is determined according to the first parameter, and then a driving module is controlled to drive a moving magnetic pole component to move to adjust an air gap space to the target air gap, so that dynamic and accurate adjustment of the air gap can be realized, the magnetic core in the magnetic circuit assembly is effectively prevented from being caused to exceed a saturation threshold due to a sudden rise of the fault current, and the stability of the inductance value of the commutation device is maintained, and the technical problems that the commutation ability of the commutation device is lost due to saturation of the magnetic core and the current transfer failure rate is high in the related art are improved.

Description

Technical Field

[0001] This application relates to the field of electronic technology, and in particular to an air gap converter. Background Technology

[0002] In related technologies, converter devices typically employ iron-silicon alloys (Fe-6.5Si) or ferrite cores with a silicon content of 6.5%, which have low saturation magnetic flux densities (e.g., Fe-6.5S has a flux density of 1.05T, while ferrite cores typically have a saturation magnetic flux density <0.5T). When the fault current surges dramatically from the normal operating current, the core flux density jumps sharply from 0.6T to 1.8T, far exceeding the saturation threshold, causing the inductance to plummet from 10μH to 2μH, resulting in a complete loss of commutation capability. In these related technologies, the inductance fluctuation of converter devices under fault current conditions reaches 40%, directly leading to a current transfer failure rate as high as 15%. Summary of the Invention

[0003] This application provides an air gap converter device, which improves the technical problems in related technologies such as loss of converter capability and high current transfer failure rate caused by magnetic core saturation in converter devices.

[0004] An embodiment of this application provides an air gap converter, comprising: a magnetic circuit assembly, a controller, and a drive module; the magnetic circuit assembly includes at least one magnetic core and a moving magnetic pole component; the magnetic core and a first end face of the moving magnetic pole component form an air gap space; the moving magnetic pole component is connected to the drive module;

[0005] The controller is configured to acquire a first parameter related to the fault current in the DC power grid; determine a target air gap based on the first parameter; determine the drive voltage of the drive module based on the target air gap; and control the moving magnetic pole component to move based on the drive voltage to adjust the air gap space to the target air gap to achieve commutation.

[0006] In the embodiments of this application, a first parameter related to the fault current in the DC power grid is obtained by the controller, and a target air gap is determined based on the first parameter. Then, the drive module is controlled to drive the moving magnetic pole component to move to adjust the air gap space to the target air gap. This enables dynamic and precise adjustment of the air gap, effectively preventing the magnetic core in the magnetic circuit assembly from exceeding the saturation threshold due to a sudden increase in fault current. This maintains the stability of the inductance value of the converter device and improves the technical problems in related technologies where the converter device loses its commutation capability and has a high current transfer failure rate due to magnetic core saturation. Attached Figure Description

[0007] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0009] Figure 1 A schematic diagram of a structure of an air gap converter provided in an embodiment of this application;

[0010] Figure 2 A schematic diagram of another structure of the air gap converter provided in the embodiments of this application;

[0011] Figure 3 A schematic diagram of a magnetic core provided for an embodiment of this application;

[0012] Figure 4 A schematic diagram showing the positions of the conductor and magnetic core provided for embodiments of this application;

[0013] Figure 5 A schematic diagram showing the positions of the moving magnetic pole component and the magnetic core provided for embodiments of this application;

[0014] Figure 6 This is another schematic diagram of a magnetic core provided for an embodiment of this application. Detailed Implementation

[0015] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0016] Furthermore, it should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of this application. In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operation, specifically the directions shown in the accompanying drawings; while "inner" and "outer" refer to the outline of the device.

[0017] DC converters are the core execution units for fault protection in renewable energy power grids, and their performance directly determines the reliability and efficiency of current transfer. In renewable energy DC power grids, fault currents are characterized by rapid rise times (up to 20kA / μs), high peak values, and abundant high-frequency components (10-100kHz). Current DC converters in related technologies struggle to adapt to these characteristics, exhibiting three fundamental flaws that restrict the overall performance of fault protection:

[0018] First, magnetic core saturation leads to commutation failure: In related technologies, there is no effective magnetic saturation prevention mechanism for commutation devices, and the commutation capacity is easily lost, which directly leads to a high current transfer failure rate.

[0019] Secondly, high-frequency losses pose challenges to thermal management: Eddy current losses in related magnetic cores increase significantly at frequencies above 10kHz. For example, the loss density of ferrite cores at 10kHz can reach 1280kW / m³. 3 This can cause the device temperature to rise by more than 80K. To maintain normal operation, an additional liquid cooling system must be configured, which not only increases the overall volume by 30% but also increases system complexity and cost. Meanwhile, the static loss of the converter in related technologies is >50W, which cannot meet the low-power operation requirements of new energy systems.

[0020] Third, the dynamic response lags behind the fault development: most related technologies use motor-driven air gap regulation, whose response delay is usually >50μs, which cannot match the fault current rise rate of 20kA / μs in new energy systems. When a fault occurs, the regulation speed lags behind the current change, causing the short-circuit current peak to run out of control (often exceeding 20 times the rated value), which can easily trigger system-level cascading failures and cause significant economic losses.

[0021] Figure 1 A schematic diagram of the air gap converter provided in the embodiments of this application is shown below. Figure 1 As shown, the air gap converter includes: a magnetic circuit assembly 100, a controller 200, and a drive module 300; the magnetic circuit assembly 100 includes at least one magnetic core 101 and a moving magnetic pole component 102; the magnetic core 101 and the first end face of the moving magnetic pole component 102 form an air gap space 103; the moving magnetic pole component 102 is connected to the drive module 300; the controller 200 is used to acquire a first parameter related to the fault current in the DC power grid; determine the target air gap according to the first parameter; determine the drive voltage of the drive module based on the target air gap; and control the moving magnetic pole component 102 to move based on the drive voltage to adjust the air gap space 103 to the target air gap to achieve commutation.

[0022] In this embodiment, the air-gap converter can be determined according to actual conditions and is not limited here. As an example, the air-gap converter can be a device that realizes fault current commutation by adjusting the size of the air gap space 103 in the magnetic circuit in a DC power grid. The air-gap converter can adjust the inductance characteristics by dynamically changing the magnetic reluctance of the magnetic circuit to adapt to changes in fault current. The magnetic circuit assembly 100 can be a component used to form the magnetic circuit in the DC power grid. The magnetic core 101 can be determined according to actual conditions and is not limited here. As an example, the magnetic core 101 can be a fixed magnetic conductive component in the magnetic circuit assembly 100. The magnetic core 101 can typically be made of a high permeability material, such as Fe-6.5Si magnetic core or nanocrystalline alloy. The number of magnetic cores 101 can be determined according to actual conditions and is not limited here.

[0023] In this embodiment, the moving magnetic pole component 102 can be determined according to actual conditions and is not limited here. As an example, the moving magnetic pole component 102 can be a movable magnetic component in the magnetic circuit assembly 100. The first end face of the moving magnetic pole component 102 can be the surface opposite to the magnetic core 101, and the second end face of the moving magnetic pole component 102 can be connected to the drive module 300. The position of the moving magnetic pole component 102 can be adjusted by the drive module 300 to change the distance between the first end face of the moving magnetic pole component 102 and the magnetic core 101, thereby forming an adjustable air gap space 103. It should be noted that the adjustment range of the air gap space 103 can be 0.015mm-0.08mm.

[0024] In some embodiments, to improve the wear resistance of the moving magnetic pole component 102, a diamond-like carbon (DLC) coating with a hardness greater than 2000 HV can be sprayed onto the surface of the moving magnetic pole component 102. Actual testing showed that at 10... 6 After this operation, the wear of the moving magnetic pole component 102 is less than 0.1 μm, and its service life is increased to 10 years. 7 This (five times that of metal surface treatment methods in related technologies) ensures the long-term stability and reliability of the air gap converter.

[0025] In this embodiment, the drive module 300 can be determined according to actual conditions and is not limited here. As an example, the drive module 300 can be a module that responds to the command sent by the controller 200, including the drive voltage, and converts the drive voltage into mechanical displacement to drive the moving magnetic pole component 102 to move. It should be noted that the adjustment speed of the drive module 300 can be 0.11-0.33 m / s. The first parameter can be used to reflect the state of the fault current. The first parameter can be determined according to actual conditions and is not limited here. As an example, the first parameter can be a characteristic parameter related to the fault current in the DC grid. For example, the first parameter can be the current parameter, the rate of change of current (di / dt) parameter, the frequency parameter, etc. of the fault current. The target air gap can be the size of the air gap space 103 used to enable the air gap converter to achieve effective commutation, calculated by the controller 200 according to the first parameter. For example, the target air gap can be δ 目标 .

[0026] Specifically, an initial air gap space can be formed by the magnetic core 101 and the first end face of the moving magnetic pole component 102, with the air gap of the initial air gap space being the initial air gap δ0, thus constructing a basic magnetic circuit. When a fault current occurs in the DC power grid, the controller 200 can acquire a first parameter related to the fault current, and can calculate a target air gap to avoid saturation of the magnetic core 101 and maintain commutation capability based on the first parameter. The drive voltage required by the drive module can be determined based on the target air gap; for example, the drive voltage can be V. 驱动 The moving magnetic pole component 102 is driven to move along a preset path to the target position, so that the air gap space 103 is adjusted to the target air gap. The inductance characteristics of the air gap converter are adjusted by changing the magnetic circuit reluctance, so as to realize the effective commutation of the fault current.

[0027] In some embodiments, the air gap converter further includes a first branch for conducting the DC current transmitted by the DC bus to the load, wherein the magnetic circuit assembly 100 may be disposed in the first branch; and a second branch for conducting the fault current when the DC current is a fault current, wherein the second branch may be a solid branch, and the fault current may be conducted in the second branch when the driving voltage controls the moving magnetic pole component 102 to move to adjust the air gap space 103 to the target air gap, thereby realizing the commutation of the fault current from the first branch to the second branch.

[0028] This application sets up a magnetic circuit assembly 100, a controller 200, and a drive module 300. The controller 200 dynamically adjusts the air gap space 103 between the magnetic core 101 and the moving magnetic pole component 102 according to the first parameter of the fault current. This achieves precise and real-time adjustment of the air gap, which can effectively cope with the sudden change of fault current in the DC power grid, avoid commutation failure caused by the saturation of the magnetic core 101, and improve the reliability and adaptability of the air gap converter.

[0029] In one embodiment, the first parameter includes a current parameter; the air gap converter further includes a current monitoring component; the current monitoring component is connected to the controller; the current monitoring component is used to monitor the current parameter; the controller 200 is also used to determine the target air gap based on the current parameter.

[0030] In this embodiment, the current parameter can be a parameter characterizing the magnitude of the fault current, for example, the current parameter can be the fault current I; the current monitoring component can be a component that collects the current parameter based on the first sampling period. The current parameter can be used to calculate the current change rate parameter. The current parameter and the current change rate parameter can provide accurate current dynamic characteristic basis for magnetic circuit adjustment, ensuring the pertinence and effectiveness of the adjustment strategy. In some embodiments, the first parameter may also include the current change rate parameter; the controller can determine the current change rate parameter based on the first sampling period and the current parameter.

[0031] Specifically, the fault current parameters can be obtained in real time through the current monitoring component; the controller can calculate the target air gap based on the current parameters, and the calculation process of the target air gap is shown in formula (1):

[0032]

[0033] Where, δ 目标 The target air gap is μ0; μ0 is the free permeability, μ0 = 4π × 10⁻⁶. -7 H / m; A is the cross-sectional area of ​​the magnetic core, A = 2500 mm. 2 N is the number of turns in the coil, N = 1; B max B is the saturation flux density threshold of the Fe-6.5Si magnetic core. max =1.05T; δ0 is the initial air gap, δ0 = 0.02mm. In some embodiments, the target air gap can be 0.028mm.

[0034] In the embodiments of this application, by setting a current monitoring component for monitoring current parameters, the controller determines the target air gap based on the current parameters, and can dynamically adjust the air gap space 103 according to the actual magnitude and variation characteristics of the fault current, ensuring that the magnetic flux density of the magnetic core 101 is always below the saturation threshold, thereby improving the technical problem in the related art that the converter device cannot accurately adjust the air gap according to the current parameters, resulting in the saturation of the magnetic core 101, the sharp drop in inductance value, and the loss of commutation capability.

[0035] As an application example, Figure 2 Another structural schematic diagram of the air gap converter provided in the embodiments of this application, as shown below. Figure 2As shown, the air-gap converter may further include a monitoring module 400. The monitoring module 400 is a module for real-time acquisition of a first parameter related to the fault current. By monitoring the characteristics of the fault current, the target air gap for achieving commutation is determined. The monitoring module 400 may include a current monitoring component and a frequency monitoring component. The current monitoring component may be a Hall sensor 401, which acquires current parameters, such as the fault current I, by sensing changes in magnetic flux in the magnetic circuit. The controller can calculate the current change rate di / dt from the fault current I. The Hall sensor 401 has a bandwidth of 10MHz and can acquire fault current parameters accurately and in real-time. The magnetic core 101 may be an Fe-6.5Si magnetic core 110.

[0036] As an application example, the first parameter may also include a frequency parameter, which can be a parameter characterizing the frequency components in the fault current, such as the dominant frequency f. The frequency monitoring component can be a component that acquires the frequency parameter based on the second sampling period. For example, the frequency monitoring component can be a Fast Fourier Transform Analyzer (FFT) analyzer, which can perform spectral analysis on the fault current to extract frequency features. The FFT analyzer 402 can be used to resolve the dominant frequency f in the frequency range of 10-100kHz, with a frequency resolution of 0.1Hz and a resolution error ≤1%, providing reliable high-frequency characteristic data support for high-frequency loss calculation and precise control of the commutation voltage.

[0037] Here, the moving magnetic pole component 102 can be made of 1J22 cobalt-iron alloy material for the moving magnetic pole 120. The saturation magnetic flux density of this material is Bs = 2.4T, which is 2.3 times that of the Fe-6.5Si magnetic core. Under the action of a fault current of 5kA, the magnetic flux density of the moving magnetic pole component 102 is only 0.8T, which is far lower than the saturation value of 2.4T of the moving magnetic pole 120, effectively avoiding the sudden change in magnetic reluctance caused by the saturation of the moving magnetic pole component 102.

[0038] In some embodiments, the controller 200 can determine the target air gap based on current parameters and frequency parameters. The controller 200 can combine the fault intensity reflected by the current parameters and the frequency characteristics reflected by the frequency parameters to comprehensively calculate the target air gap. For example, when the current parameters indicate a large fault current and the frequency parameters indicate the presence of high-frequency components, the controller 200 will determine a larger target air gap to simultaneously avoid core 101 saturation and reduce high-frequency losses.

[0039] In the embodiments of this application, by setting up a monitoring module 400, using a current monitoring component to monitor current parameters and a frequency monitoring component to monitor frequency parameters, the controller 200 determines the target air gap based on the current parameters and frequency parameters. This enables multi-dimensional feature identification of the fault current, making the determination of the target air gap take into account the intensity, rate of change, and frequency characteristics of the fault current, which is more in line with the needs of actual fault scenarios. This improves the technical problems in related technologies where adjusting the air gap based on only a single parameter results in insufficient accuracy and difficulty in adapting to complex faults.

[0040] In one embodiment, the air gap converter further includes a displacement monitoring component connected to the controller; the displacement monitoring component is used to monitor the first air gap of the air gap space 103; the controller is also used to determine the driving voltage based on the first air gap, the target air gap and preset control parameters.

[0041] In this embodiment, the air gap converter is equipped with a displacement monitoring component, which can be a component used to monitor the current size of the air gap space 103 in real time. As an application example, such as... Figure 2 As shown, the displacement monitoring component can be a laser displacement sensor 500, and the monitoring accuracy of the laser displacement sensor 500 can reach ±0.001mm. The first air gap can be the current actual air gap of the air gap space 103 monitored by the displacement monitoring component, that is, the actual air gap δ between the magnetic core 101 and the first end face of the moving magnetic pole component 102. 实际 The laser displacement sensor 500 can feed back the actual air gap to the controller 200. The preset control parameters can be control algorithm parameters pre-set in the controller to achieve closed-loop air gap regulation, such as the proportional coefficient and integral time constant in a proportional-integral (PI) control algorithm. These preset control parameters can be used to optimize control accuracy and response speed. The driving voltage can be a PI control signal.

[0042] Specifically, the first air gap of the monitored air gap space 103 can be obtained in real time through the displacement monitoring component. The controller can substitute the first air gap, the target air gap, the proportional coefficient, and the integral time constant into the preset control algorithm (e.g., PI adjustment formula) to calculate the driving voltage required by the drive module 300. The drive module 300 drives the moving magnetic pole component 102 to move based on the driving voltage, so that the air gap is gradually adjusted from the first air gap to the target air gap. At the same time, the displacement monitoring component continuously feeds back the air gap change, forming a closed-loop regulation. The calculation process of the driving voltage is shown in formula (2):

[0043]

[0044] Among them, V 驱动 K is the driving voltage. p K is the proportionality coefficient. p=50; T i Let T be the integration time constant. i = 0.5 microseconds (μs).

[0045] In the embodiments of this application, by setting a displacement monitoring component for monitoring the first air gap of the air gap space 103, the controller determines the driving voltage based on the first air gap, the target air gap and preset control parameters, which can realize closed-loop control of air gap adjustment, and ensure that the air gap converges to the target air gap within 0.3μs, realize the rapid and stable adjustment of the inductor, and ensure the dynamic response performance of the air gap converter.

[0046] It should be noted that, to ensure the magnetic core 101 remains unsaturated throughout the entire fault range, this application employs a combined PI feedback and feedforward control algorithm to dynamically constrain the magnetic flux density, ensuring that the magnetic flux density is less than or equal to the saturation threshold of 1.05T for the Fe-6.5Si magnetic core 101. The feedforward control algorithm includes calculating the target air gap based on real-time monitored current parameters. The PI feedback control algorithm includes calculating the actual air gap δ detected by the laser displacement sensor 500. 实际 The piezoelectric drive voltage is adjusted in real time. The control parameter is set as follows: proportional coefficient K. p =50, integration time T i =0.5μs. This control strategy ensures that the air gap converges to the target air gap within 0.3μs, achieving rapid and stable adjustment of the inductor and guaranteeing the dynamic response performance of the air gap converter.

[0047] In some embodiments, the controller calculates the magnetic flux density B in real time. When B > 1.0T is detected, the air gap is increased in advance. Through this proactive prevention mechanism, it is ensured that B is less than or equal to 1.05T throughout the entire fault range, effectively avoiding the inductance surge caused by the saturation of the magnetic core 101 and guaranteeing the commutation performance of the air gap converter.

[0048] In one embodiment, the drive module 300 includes a deformable dielectric component and a lever component. The deformable dielectric component is connected to the lever component, which is connected to the second end face of the moving magnetic pole component 102. The first end face and the second end face are two opposite end faces of the moving magnetic pole component 102. The deformable dielectric component is used to generate a first displacement based on the drive voltage. The lever component is used to generate a second displacement based on the first displacement. The controller is also used to control the moving magnetic pole component 102 to move the second displacement based on the drive voltage, so as to adjust the air gap space 103 to the target air gap to achieve commutation.

[0049] In this embodiment, the drive module 300 can be an execution unit that converts electrical signals into mechanical displacement to drive the moving magnetic pole component 102 to move. The drive module 300 can achieve precise driving of the moving magnetic pole component 102 through the synergistic effect of the deformable dielectric component and the lever component, thereby adjusting the air gap space 103. The deformable dielectric component can be a component in the drive module 300 that converts driving voltage into mechanical displacement based on the piezoelectric effect, such as a piezoelectric component, which can be a piezoelectric drive mechanism. Under different driving voltages, the piezoelectric component can generate different first displacements. The first displacement can be the original displacement directly generated by the piezoelectric component under the driving voltage, and the first displacement is usually a small displacement. As an application example, such as... Figure 2 As shown, the piezoelectric component can use stacked (PZT-5H) type piezoelectric ceramics. This PZT-5H type piezoelectric ceramic 301 has the characteristics of fast response speed and high displacement accuracy, d33=650pC / N, and can output a displacement of 0.03mm under a driving voltage of 100V.

[0050] In this embodiment, the lever assembly can be a mechanical structure in the drive module 300 used to amplify the first displacement. It amplifies the first displacement of the piezoelectric component into a larger second displacement through the lever principle to meet the movement requirements of the moving magnetic pole component 102. The second displacement can be the amplified displacement output by the lever assembly, and the second displacement is related to the first displacement and the amplification factor of the lever assembly. As an application example, such as... Figure 2 As shown, the lever assembly can be a 1:1000 lever 302 with a stiffness coefficient greater than 1GN / m, enabling air gap adjustment accuracy of ±0.001mm. Actual measurements show that the response time of the drive module 300 is only 0.25μs, fully meeting the adjustment requirements of a 20kA / μs fault current, ensuring that magnetic circuit reconstruction can be completed in the early stages of fault development, thus achieving rapid control of the fault current.

[0051] In this embodiment, the second end face of the moving magnetic pole component 102 can be the surface on the moving magnetic pole component 102 opposite to the first end face. The second end face can serve as the connecting end face of the lever assembly, used to receive the second displacement transmitted by the lever assembly to drive the entire moving magnetic pole component 102 to move. The first end face and the second end face can be two opposite end faces in the moving magnetic pole component 102, that is, the first end face and the second end face are spatially distributed opposite each other.

[0052] In the embodiments of this application, when the controller outputs a driving voltage, the deformable dielectric component generates a first displacement under the action of the driving voltage; after receiving the first displacement, the lever component amplifies the first displacement into a second displacement through mechanical transmission; since the lever component is connected to the second end face of the moving magnetic pole component 102, the second displacement directly drives the moving magnetic pole component 102 to move along a preset path, so that the air gap space 103 between the first end face and the magnetic core 101 changes accordingly, and finally adjusts to the target air gap to achieve commutation. It can realize the use of the fast response characteristics of the deformable dielectric component and the displacement amplification function of the lever component to obtain a large displacement that meets the requirements under a small voltage drive, so that the air gap adjustment has both high precision and fast response, thereby improving the technical problem in the related technology that the driving method is difficult to balance the adjustment accuracy and response speed, resulting in poor commutation effect.

[0053] In one embodiment, the magnetic core 101 is a U-shaped magnetic core including a first vertical arm, a second vertical arm, and a bottom; the first vertical arm, the bottom, and the second vertical arm form an inner hole; the air gap converter further includes a conductor, which passes through the inner hole perpendicular to the first vertical arm and the second vertical arm and parallel to the bottom.

[0054] In this embodiment, the magnetic core 101 can be a U-shaped magnetic core 101; the magnetic core 101 can include a vertically extending first arm, a second arm, and a horizontally connected bottom, forming a symmetrical magnetic conductive channel. The first arm can be a vertical arm on one side of the U-shaped magnetic core, for example, the left arm; the second arm can be a vertical arm on the other side of the U-shaped magnetic core, for example, the right arm. The second arm can be symmetrically distributed with the first arm, together enclosing the inner hole. The bottom can be a horizontal portion connecting the lower ends of the first arm and the lower ends of the second arm. The inner hole can be a hollow area enclosed by the first arm, the bottom, and the second arm, and the inner hole can provide space for conductors to pass through. The first arm or the second arm can form the inner hole wall. The conductor can be a current-carrying conductive component (e.g., copper busbar, busbar, etc.), and the direction of conductor passage can be perpendicular to the vertical extension direction of the first and second arms and parallel to the horizontal extension direction of the bottom.

[0055] As an application example, Figure 3 This is a schematic diagram of a magnetic core provided for an embodiment of this application. Figure 4 A schematic diagram of the conductor and magnetic core positions provided for embodiments of this application is shown below. Figure 3 and Figure 4 As shown, the left arm 1011, right arm 1012, and bottom 1013 of the U-shaped magnetic core can form a closed magnetic circuit. The total length of the U-shaped magnetic core can be 80mm, and the cross-sectional area is 2500mm². 2 The inner diameter can be 25mm; for example Figure 2 and Figure 3As shown, a single-turn copper busbar 104 can be used as a single-turn conductor. The copper busbar 104 can be 10mm wide, 8mm thick, and have a cross-sectional area of ​​80mm². 2 The copper busbar passes directly through the inner hole of the magnetic core 101, forming a single-turn coil structure. The copper busbar can vertically penetrate the 25mm inner hole at the bottom of the magnetic core 101, and the gap between the copper busbar and the left or right arm can be 7.5mm to ensure complete magnetic flux coupling. This design allows for a current density of 187.5A / mm². 2 Far exceeding the conventional winding 5A / mm 2 The current density is sufficient to effectively meet the needs of high current transmission. The calculation process of the inductance value of the single-turn through-core structure is shown in formula (3):

[0056]

[0057] Where, μ r The relative permeability (μ) of the Fe-6.5Si magnetic core. r =5×10 4 H / m; l is the magnetic circuit length, l = 80 mm. When δ = 0.028 mm,

[0058] In the embodiments of this application, by configuring the magnetic core 101 as a U-shaped magnetic core including a first arm, a second arm, and a bottom, with the first arm, bottom, and second arm forming an inner hole, and by having the conductor pass through the inner hole perpendicular to the first and second arms and parallel to the bottom, the current magnetic field can be efficiently closed along a predetermined path of the U-shaped magnetic core, thus enhancing the magnetic coupling efficiency. Here, by configuring the conductor as a single-turn copper busbar, the DC resistance of a single-turn copper busbar is only 0.21 μΩ. Under a fault current of 5 kA, according to Joule's law P = I 2 According to R calculations, its Joule heat loss is only 47.25W, which significantly reduces energy loss compared to the 350W loss of multi-turn windings, improves the efficiency of the air gap converter, and achieves low-loss conduction.

[0059] In one embodiment, the end face of the second vertical arm of the U-shaped magnetic core forms an air gap space 103 with the first end face of the moving magnetic pole component 102.

[0060] In this embodiment, the air gap space 103 is constructed based on the end face cooperation between the U-shaped magnetic core and the moving magnetic pole component 102, and a gap region with dynamically adjustable magnetic resistance is formed through the relative surfaces of the two.

[0061] Among them, the end face of the second arm of the U-shaped magnetic core can be the surface of the top of the second arm that has been precision machined; the first end face of the moving magnetic pole component 102 can be the surface of the moving magnetic pole component 102 facing the end face of the second arm, and the first end face can be set parallel to the end face of the second arm; the air gap space 103 can be the gap area between the first end face and the end face of the second arm, and the air gap of the air gap space 103 can be used to determine the magnitude of the magnetic reluctance in the magnetic circuit.

[0062] In the embodiments of this application, by forming an air gap space 103 between the end face of the second vertical arm of the U-shaped magnetic core and the first end face of the moving magnetic pole component 102, the magnitude of the magnetic reluctance can be adjusted by adjusting the air gap of the air gap space 103. This allows the change in the size of the air gap to directly and efficiently change the magnetic circuit impedance, thereby improving the technical problems in related technologies such as the ambiguity of the magnetic reluctance adjustment point and the low efficiency of the air gap in magnetic circuit control, which leads to poor commutation accuracy.

[0063] In one embodiment, the surface of the conductor is provided with a silver plating layer to increase the resistivity of the conductor.

[0064] In this embodiment, the silver plating layer can be a silver film deposited on the surface of the conductor. The silver plating layer can be prepared using processes such as electroplating and electroless plating. The current conduction path on the conductor surface can be altered through microstructure (e.g., porosity, texturing) or compositional design (e.g., doping with insulating phases). Resistivity is a physical quantity characterizing a conductor's ability to impede current. The silver plating layer can increase the overall equivalent resistivity of the conductor by increasing the equivalent resistance to current transmission (e.g., path current flow, interface scattering). The thickness of the silver plating layer can be determined according to actual conditions and is not limited here. As an example, the thickness of the silver plating layer can be 5 μm.

[0065] To mitigate the impact of the high-frequency skin effect, the copper busbar surface is silver-plated with a thickness of 5 μm. This ensures that the increase in AC resistance at 100 kHz is controlled to within 1.5 times, guaranteeing stable operation of the air-gap converter in high-frequency scenarios and improving its high-frequency adaptability. In the embodiments of this application, by applying a silver plating layer to the conductor surface to increase its resistivity, directional control of the conductor resistivity can be achieved, altering current transmission characteristics (such as attenuation rate and high-frequency component proportion). This addresses the technical problem in related technologies where the conductor resistivity is fixed and difficult to adapt to the dynamic control requirements of current characteristics in air-gap converters.

[0066] In one embodiment, the surface of the U-shaped magnetic core is provided with a nanocrystalline coating to increase the resistivity of the U-shaped magnetic core, or the U-shaped magnetic core is a nanocrystalline alloy.

[0067] In this embodiment, the surface state of the U-shaped magnetic core directly affects electrical characteristics such as eddy current loss. The nanocrystalline coating can be a thin film composed of nanoscale (typically 1-100 nm) crystal particles deposited on the surface of the U-shaped magnetic core. For example, the nanocrystalline coating can be an iron-silicon-boron (Fe-Si-B) nanocrystalline coating. The nanocrystalline coating can be prepared by processes such as magnetron sputtering and sol-gel. The small crystal particles and dense grain boundaries of the nanocrystalline coating can significantly hinder current conduction. The nanocrystalline coating or nanocrystalline alloy can increase the effective resistivity of the U-shaped magnetic core by increasing the current conduction resistance on the surface of the U-shaped magnetic core, thereby suppressing eddy currents (especially high-frequency eddy currents). The thickness of the nanocrystalline coating can be determined according to the actual situation and is not limited here. As an example, the thickness of the nanocrystalline coating can be 50 ± 5 μm.

[0068] As an application example, to reduce high-frequency eddy current losses, a 50±5μm Fe-Si-B nanocrystalline coating was prepared on the surface of magnetic core 101 using magnetron sputtering. This coating increased the resistivity of magnetic core 101 from the original 47μΩ·cm to 142μΩ·cm, an increase of 3 times. Experimental results show that at a frequency of 10kHz, the eddy current loss of magnetic core 101 using this design decreased from 25W / kg to 2.2W / kg, significantly reducing the temperature rise of the air gap converter and improving its heat dissipation performance and operational stability. The calculation process for eddy current losses is shown in formula (4):

[0069]

[0070] Among them, P e d is eddy current loss; f is frequency; B is magnetic flux density; d is coating thickness; ρ is coating resistivity, ρ = 142 × 10⁻⁶. -6 Ω·m.

[0071] In the embodiments of this application, by providing a nanocrystalline coating on the surface of the U-shaped magnetic core 101 to increase the resistivity of the U-shaped magnetic core, the high grain boundary density of the nanocrystalline coating can be used to suppress eddy currents (especially high-frequency eddy currents) in the U-shaped magnetic core, reduce eddy current losses, and thus improve the technical problems in the related art where the U-shaped magnetic core has large eddy current losses and excessive temperature rise in high-frequency scenarios, leading to a decrease in the reliability of the air gap converter.

[0072] In one embodiment, the first end of the first end face of the moving magnetic pole component 102 is fixedly connected to the first upright arm, and the second end of the first end face of the moving magnetic pole component 102 forms an air gap space 103 with the second upright arm. The first end and the second end are the two opposite ends of the first end face of the moving magnetic pole component 102.

[0073] In the embodiments of this application, by fixing the first end of the first end face of the moving magnetic pole component 102 to the first upright arm, and forming an air gap space 103 with the second end of the first end face and the second upright arm, the moving magnetic pole component 102 can be stabilized with the first end as a fixed fulcrum, so that the movement of the second end only changes the air gap size in a directional manner without destroying the overall continuity of the magnetic circuit, thereby improving the technical problem in the related art that the moving magnetic pole component 102 is prone to shaking when it moves, resulting in low air gap adjustment accuracy or magnetic circuit interruption.

[0074] In one embodiment, the second end of the moving magnetic pole component 102 slides relative to the second vertical arm via a guide rail.

[0075] The guide rail can be a guiding structure used to limit the movement direction of the second end of the moving magnetic pole component 102. For example, the guide rail can be a ceramic guide rail. The guide rail can be connected to the base, and the second end can be guided to slide along a preset path through the cooperation between the guide rail and the base, such as using a linear guide rail or an arc-shaped guide rail. As an application example, Figure 5 A schematic diagram showing the positions of the moving magnetic pole component and the magnetic core provided for embodiments of this application is shown below. Figure 5 As shown, the moving magnetic pole component 102 forms an adjustable air gap (δ) with the right arm end face of the U-shaped magnetic core. The air gap ranges from 0.015 to 0.08 mm, and low-friction sliding is achieved through a ceramic guide rail with a friction coefficient of 0.003. The moving magnetic pole can be connected to piezoelectric ceramics and a 1:1000 lever.

[0076] It should be noted that, Figure 6 Another schematic diagram of the magnetic core provided for an embodiment of this application, as shown below. Figure 6 As shown, since the first end of the moving magnetic pole component 102 is fixed to the left arm 1011, during the sliding displacement of the second end relative to the right arm 1012, the angle between the moving magnetic pole component 102 and the magnetic core 101 gradually increases, so the preset path of the second end is an arc-shaped path.

[0077] This application achieves precise control of the movement trajectory of the second end of the moving magnetic pole component 102 by sliding displacement relative to the second vertical arm via the guide rail and utilizing the guiding constraint effect of the guide rail, thus avoiding swaying or jamming during the sliding process. This provides structural protection for the stable adjustment of the air gap space 103 and improves the operational reliability of the air gap converter.

[0078] Here, the moving magnetic pole component 102 is processed by wire electrical discharge machining, and the surface roughness can reach Ra0.02μm. When used with ceramic guide rail, the coefficient of friction is only 0.003, which ensures smooth movement and high-precision control of the moving magnetic pole during the air gap adjustment process.

[0079] In the embodiments of this application, by sliding the second end of the moving magnetic pole component 102 relative to the second upright arm through the guide rail, the movement trajectory of the second end can be constrained by the guiding effect of the guide rail, ensuring that the air gap space 103 remains uniform and parallel stable during the adjustment process, thereby improving the technical problem in the related art that the moving magnetic pole component 102 is prone to displacement when sliding, resulting in uneven air gap or decreased adjustment accuracy.

[0080] In some embodiments, the air-gap converter is subjected to a temperature cycling test (-40 to 125°C): the air-gap converter is placed in a temperature environment of -40 to 125°C for 1000 cycles. After the test, the nanocrystalline coating shows no peeling, the resistivity change is <5%, and the magnetic properties remain stable, enabling it to adapt to the operating requirements under different temperature environments. The air-gap converter is also subjected to a mechanical shock test (1000g / 1ms): after applying a mechanical shock of 1000g / 1ms to the air-gap converter, the structure shows no deformation, and the air gap adjustment accuracy can still be maintained within ±0.001mm, meeting the operating requirements under harsh conditions and ensuring the normal operation of the air-gap converter under mechanical shock.

[0081] In some embodiments, staged commutation performance verification can be performed. For example, in a scenario of a 1500V system and a 5kA fault current, the staged commutation performance of the device was verified in detail. Table 1 shows the staged commutation performance data.

[0082] Table 1

[0083]

[0084]

[0085] This application belongs to the field of high-voltage direct current (HVDC) power system protection, specifically involving a magnetically reconfigurable dynamic air-gap converter device for 1500V-3500V renewable DC power grids. As a core component for fault current transfer, it achieves unsaturated operation, low-loss conversion, and sub-microsecond response across the entire fault range through innovative magnetic circuit materials and high-precision adjustment technology. This is achieved through a synergistic design of "magnetic circuit material innovation + piezoelectric drive + closed-loop control," utilizing innovative magnetic circuit materials (nanocrystalline coating, 1J22 magnetic poles), high-precision piezoelectric drive, and closed-loop control. This solves the problems of core saturation, high high-frequency loss, and dynamic response lag in related converter devices, realizing efficient transfer of DC fault current. As a high-performance fundamental component, it provides a highly reliable, low-power conversion solution for renewable DC power grids, possessing significant engineering application value. It provides high-performance foundational support for DC fault protection systems in photovoltaic power plants, energy storage systems, and rail transit scenarios.

[0086] It should be clarified that this application, as a high-performance basic component, mainly supports subsequent system-level applications (such as fault disconnection timing control, arc extinguishing coordination, etc.) and does not involve a complete fault disconnection or arc extinguishing process.

[0087] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0088] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0089] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0090] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. An air gap converter, characterized in that, include: A magnetic circuit assembly, a controller, and a drive module; the magnetic circuit assembly includes at least one magnetic core and a moving magnetic pole component; The magnetic core and the first end face of the moving magnetic pole component form an air gap space; the moving magnetic pole component is connected to the drive module; The controller is used to acquire a first parameter related to the fault current in the DC power grid; and determine the target air gap based on the first parameter. The driving voltage of the driving module is determined based on the target air gap; The moving magnetic pole component is moved based on the driving voltage to adjust the air gap space to the target air gap to achieve commutation.

2. The air gap converter according to claim 1, characterized in that, The first parameter includes a current parameter; the air gap converter further includes a current monitoring component; the current monitoring component is connected to the controller; The current monitoring component is used to monitor the current parameters; The controller is also configured to determine the target air gap based on the current parameters.

3. The air gap converter according to claim 1, characterized in that, The air gap converter also includes a displacement monitoring component, which is connected to the controller. The displacement monitoring component is used to monitor the first air gap of the air gap space; The controller is further configured to determine the driving voltage based on the first air gap, the target air gap, and preset control parameters.

4. The air gap converter according to claim 1, characterized in that, The drive module includes a deformable dielectric component and a lever component. The deformable dielectric component is connected to the lever component, and the lever component is connected to the second end face of the moving magnetic pole component. The first end face and the second end face are two opposite end faces of the moving magnetic pole component. The deformable dielectric component is used to generate a first displacement based on the driving voltage; The lever assembly is used to generate a second displacement based on the first displacement; The controller is also used to control the moving magnetic pole component to move the second displacement based on the driving voltage, so as to adjust the air gap space to the target air gap to achieve commutation.

5. The air gap converter according to claim 1, characterized in that, The magnetic core is a U-shaped magnetic core including a first vertical arm, a second vertical arm, and a bottom; the first vertical arm, the bottom, and the second vertical arm form an inner hole; the air gap converter also includes a conductor, which passes through the inner hole perpendicular to the first vertical arm and the second vertical arm and parallel to the bottom.

6. The air gap converter according to claim 5, characterized in that, The end face of the second vertical arm of the U-shaped magnetic core forms an air gap space with the first end face of the moving magnetic pole component.

7. The air gap converter according to claim 5, characterized in that, The surface of the conductor is provided with a silver plating layer to increase the resistivity of the conductor.

8. The air gap converter according to claim 5, characterized in that, The surface of the U-shaped magnetic core is provided with a nanocrystalline coating to increase the resistivity of the U-shaped magnetic core, or the U-shaped magnetic core is a nanocrystalline alloy.

9. The air gap converter according to claim 5, characterized in that, The first end of the first end face of the moving magnetic pole component is fixedly connected to the first upright arm, and the second end of the first end face of the moving magnetic pole component forms the air gap space with the second upright arm. The first end and the second end are the two opposite ends of the first end face of the moving magnetic pole component.

10. The air gap converter according to claim 9, characterized in that, The second end of the moving magnetic pole component slides relative to the second vertical arm via a guide rail.

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