Method and device for calculating alternating current loss of three-phase coaxial superconducting cable

Abstract

The invention relates to a three-phase coaxial superconducting cable alternating current loss calculation method and device, and the method comprises the following steps: calculating the alternating current loss of a body part, the alternating current loss of the body part comprising the multi-order harmonic component alternating current loss solved through an analytical method; calculating asymmetric current component alternating current loss; calculating the alternating current loss of the terminal part; adding the alternating current loss of the body part, the alternating current loss of the asymmetric current component and the alternating current loss of the terminal part to obtain the alternating current loss of the three-phase coaxial superconducting cable; wherein the multi-order harmonic component alternating current loss comprises magnetic hysteresis loss generated by main current fluctuation and magnetic hysteresis loss generated by a plurality of small current fluctuations, the main current fluctuation is a sine wave with a load current fundamental wave as an amplitude, and the small current fluctuations are current fluctuations formed by harmonic current distortion. The harmonic current is obtained through an interlayer current distribution solving method. Compared with the prior art, the accuracy of a calculation result can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of power transmission and distribution, and in particular relates to a method and device for calculating AC loss of a three-phase coaxial superconducting cable. Background Art

[0002] The three-phase coaxial conductor cable has the advantages of compact structure, high transmission efficiency and low loss. It is one of the power equipment that is being vigorously researched and developed at home and abroad. The three superconducting layers (i.e., A, B, and C phase conductors) are coaxially wound on the same frame, each surrounded by an insulating layer and wrapped by a shielding layer. When the superconducting cable transmits AC current or is in an alternating magnetic field, the changing magnetic field will generate an induced electric field in the superconductor, and thus generate a certain amount of energy loss, i.e., AC loss. AC loss is one of the basic parameters that must be considered in the design and operation of superconducting cable systems. Its calculation methods mainly include analytical calculation method and numerical calculation method. At present, finite element software based on numerical calculation is often used to simulate and solve the AC loss of superconducting cables. It can more intuitively understand the current distribution and the change and distribution of AC loss. However, due to the complex spiral structure and precise material arrangement of superconducting cables, the calculation complexity of the entire calculation model is relatively high. If it also contains multiple orders of harmonic current components with different amplitudes and phases, it will be more time-consuming and labor-intensive. In addition, since the AC loss of superconducting cables is of a small order of magnitude, as the key to ensuring the accuracy of the calculation, the grid must be divided sufficiently and finely enough to obtain a more ideal calculation result, but this also greatly increases the running time of the simulation.

[0003] The Chinese patent application with the publication number CN114325122A discloses a method for measuring the AC transmission loss of a three-phase superconducting cable. The three-phase superconducting cable is led out and then isolated at high voltage. The three-phase voltage signal and phase current of the superconducting cable after high voltage isolation are measured. Then, the phase voltage and phase current of the superconducting cable are filtered. The AC loss calculation without inductive compensation is performed according to the phase voltage and phase current after filtering to obtain the AC transmission loss. However, when the load device is connected to the power system, it will draw electric energy from the power grid to form a load current. Due to the presence of various nonlinear loads and asymmetric loads, such as power electronic equipment (such as rectifiers, frequency converters), arc furnaces, electromagnets, etc., harmonic components and asymmetric components are introduced into the load current, which will generate additional AC losses in the superconducting cable system and reduce the transmission efficiency. Therefore, the research on superconducting cable loss cannot be limited to the research on the AC loss of the superconducting tape body under normal load current. It is necessary to design a separate AC loss calculation method to consider the influence of nonlinear load current on the AC loss of the three-phase coaxial superconducting cable system. This is of great significance for optimizing the design of superconducting cables and guiding the operation and maintenance of superconducting cables. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method and device for calculating the AC loss of a three-phase coaxial superconducting cable to improve the accuracy and comprehensiveness of the calculation results.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] The present invention provides a method for calculating AC loss of a three-phase coaxial superconducting cable, comprising the following steps:

[0007] Calculating the AC loss of the main body, wherein the AC loss of the main body includes the AC loss of multi-order harmonic components solved by an analytical method; calculating the AC loss of the asymmetric current component; calculating the AC loss of the terminal part, wherein the AC loss of the terminal part includes Joule heat loss and leakage heat loss; adding the AC loss of the main body, the AC loss of the asymmetric current component and the AC loss of the terminal part to obtain the AC loss of the three-phase coaxial superconducting cable;

[0008] Among them, the multi-order harmonic component AC loss includes hysteresis loss caused by main current fluctuations and hysteresis loss caused by multiple small current fluctuations. The main current fluctuation is a sine wave with the fundamental wave of the load current as the amplitude. The small current fluctuation is current fluctuation caused by harmonic current distortion. The harmonic current is obtained by the interlayer current distribution solution method.

[0009] Furthermore, the calculation formula of the AC loss of the multi-order harmonic components is as follows:

[0010]

[0011] Among them, Q is the AC loss of multi-order harmonic components, Q major Hysteresis losses caused by main current fluctuations, To represent the hysteresis loss caused by the i-th small current fluctuation, The self-field transmission hysteresis loss caused by the main current fluctuation, is the self-field transmission hysteresis loss caused by small current fluctuations, Q mag The external field transmission hysteresis loss generated by the current, including the external field transmission hysteresis loss caused by the main current fluctuation and external field transmission hysteresis loss caused by small current fluctuations

[0012] Furthermore, the self-field transmission hysteresis loss caused by the main current fluctuation The calculation formula is as follows:

[0013]

[0014] i i =I major / I c

[0015] Where f is the operating frequency, N j is the number of superconducting tapes in the jth layer, μ0 is the vacuum permeability, i i Is the main current relative indicator, I major is the main current fluctuation amplitude, I c is the critical current density of the superconducting cable, and n is the total number of superconducting layers.

[0016] Furthermore, the hysteresis loss of the self-field transmission caused by small current fluctuations The calculation formula is as follows:

[0017]

[0018] i i =I minor / I c

[0019] in, is the number of the ith small current fluctuation, is the self-field transmission hysteresis loss caused by the i-th small current fluctuation, i max is the number of small current types, f is the operating frequency, N j is the number of superconducting tapes in the jth layer, μ0 is the vacuum magnetic permeability, n is the total number of superconducting layers, I c is the critical current density of the superconducting cable, i i It is a relative indicator of small current, I minor It is the small current fluctuation amplitude.

[0020] Furthermore, the external field transmission hysteresis loss Q generated by the current mag The calculation formula is as follows:

[0021] Q mag =∑Q magi

[0022]

[0023] Among them, Q magi is the external field magnetization loss of the i-th layer of superconducting tape, f is the operating frequency, B i is the magnetic induction intensity at the i-th layer of superconducting cable, β i is the relative index of magnetic induction, S i is the cross-sectional area of ​​the i-th layer of superconducting tape, B zi and B θi are the axial magnetic field generated by the i-th layer of toroidal current inside the i-th layer and the toroidal magnetic field generated by the i-th layer of axial current outside the i-th layer, respectively. C is the critical current of the superconducting tape under the action of the magnetic field, μ0 is the magnetic permeability of the vacuum, and b is half the thickness of the superconducting cable tape.

[0024] Furthermore, when solving the axial magnetic field B generated by the i-th layer of circular current inside the i-th layer, zi and the toroidal magnetic field B generated by the axial current of the i-th layer outside the i-th layer θi When the main current fluctuation amplitude I major Instead of solving the current value of each layer, the calculation formula is as follows:

[0025]

[0026] Where n is the total number of superconducting layers, ε k is the relative dielectric medium, L pk and L pi is the winding pitch, r ic and r io are the inner radius and outer radius of the i-th current-carrying layer respectively.

[0027] Furthermore, the asymmetric current component AC loss includes shielding layer copper loss.

[0028] Furthermore, the calculation formula of the Joule heat loss is as follows:

[0029] W=n p I 2 R p

[0030] Where W is the Joule heat loss, n p is the number of phases of the superconducting cable, I is the single-phase current, R p It is the single-phase terminal resistance of the superconducting cable;

[0031] The calculation formula of the heat leakage loss is as follows:

[0032]

[0033] Among them, W ter is the heat leakage loss, K is the thermal conductivity, ρ is the resistivity, and T is the temperature.

[0034] Furthermore, the specific steps of the interlayer current distribution solution method are as follows:

[0035] Construct the equivalent circuit diagram of multi-layer superconducting cable, write the Kirchhoff voltage equation of each phase and each layer for each order current containing harmonic components, and combine them to obtain the Kirchhoff voltage equation matrix;

[0036] According to the Kirchhoff voltage equation matrix, the voltage of each phase is solved by using the current relationship between each phase current and the conductive layer and the shielding layer, and the current distribution of each layer is solved by using the same voltage of each layer in each phase.

[0037] The present invention also provides an electronic device, comprising a memory, a processor, and a program stored in the memory, wherein the processor implements the above method when executing the program.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The present invention proposes a method for calculating the AC loss of a three-phase coaxial superconducting cable, which decomposes the AC loss of the three-phase turnkey superconducting cable into a main body part and a terminal part and solves them separately, wherein the AC loss of the terminal part includes Joule heat loss and leakage heat loss, and the AC loss of the main body part includes multi-order harmonic component AC loss solved by an analytical method. Specifically, the multi-order harmonic component AC loss includes hysteresis loss caused by main current fluctuations and hysteresis loss caused by multiple small current fluctuations. The main current fluctuation is a sine wave with the fundamental wave of the load current as the amplitude, and the small current fluctuation is a current fluctuation formed by harmonic current distortion. The harmonic current is obtained by the interlayer current distribution solution method; in addition, the present invention also takes into account and considers the influence of asymmetric current on the AC loss of the three-phase coaxial superconducting cable, which is in line with the actual operation of the power system. Therefore, fast and accurate calculation can be achieved through the above method.

[0040] 2. The present invention solves the axial magnetic field B generated by the i-th layer of circular current inside the i-th layer. zi and the toroidal magnetic field B generated by the axial current of the i-th layer outside the i-th layer θi When the main current fluctuation amplitude I major Instead of solving the current value of each layer, the calculation process can be simplified, the calculation efficiency can be improved, and it is convenient to analyze the main influencing factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flow chart of the method of the present invention;

[0042] Figure 2 It is the current waveform after the 9th order harmonic current component is added to the sinusoidal alternating current;

[0043] Figure 3 It is the main and small hysteresis loops of the current containing the 7th order harmonic component;

[0044] Figure 4 The change of AC loss when changing the amplitude of phase A;

[0045] Figure 5 The change of AC loss when the phase of phase A is changed;

[0046] Figure 6 is the thermal conductivity of copper conductor at different temperatures;

[0047] Figure 7 is the resistivity of copper conductor at different temperatures;

[0048] Figure 8 This is a schematic diagram of the calculation results.

[0049] Among them, (8a) is the numerical value of the superconducting cable body loss, terminal Joule heat loss and terminal leakage heat loss, and (8b) is the total loss obtained by superposition. DETAILED DESCRIPTION

[0050] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0051] Example 1

[0052] This embodiment provides a method for calculating AC loss of a three-phase coaxial superconducting cable. Figure 1 As shown, the following steps are included:

[0053] S1. Calculate the AC loss of the main body.

[0054] Normally, harmonic current components are formed by the superposition of harmonic currents of multiple orders, phases, and amplitudes. When a three-phase current containing harmonic currents enters a multi-layer superconducting cable, the harmonic components also need to be shunted according to the cable structure. Therefore, the harmonic current actually distributed in each layer should also be solved by the interlayer current distribution solution method. The steps are as follows: construct an equivalent circuit diagram of a multilayer superconducting cable, write the Kirchhoff voltage equations for each phase and each layer for each order current containing harmonic components, and combine to obtain the Kirchhoff voltage equation matrix; according to the Kirchhoff voltage equation matrix, use the current size of each phase and the current relationship between the conductive layer and the shielding layer to solve the voltage size of each phase, and use the same voltage of each layer in each phase to solve the current distribution of each layer. There have been relevant studies on the interlayer current distribution solution method, and the specific steps will not be repeated in this embodiment.

[0055] The AC losses of the main body include AC losses of multi-order harmonic components, which are solved by analytical methods in this embodiment. The hysteresis loss, which accounts for most of the AC losses, comes from the change in magnetic flux caused by the change in the magnetic field. When there are harmonic components in the system, the distortion of the harmonic components on the sinusoidal current causes the originally regular waveform to have new peaks and troughs of different degrees, numbers, and positions. This means that the distorted current will produce additional flux changes, and this additional hysteresis loss does not depend on the instantaneous value of the distorted current to a large extent, but on the amplitude of each rise and fall of the distorted current. Therefore, the load current containing harmonic components is analyzed. In addition to the main current fluctuations formed by the dominant fundamental wave, several small current fluctuations will be formed due to the distortion of the harmonic components. The current waveform after the 9th-order harmonic current component is applied to the sinusoidal AC current is as follows: Figure 2 As shown, the original sinusoidal current has only one peak and one trough in one cycle, but after adding the harmonic current with a larger amplitude, 9 peaks and 9 troughs are obtained.

[0056] The load current under the superposition of multi-order harmonic currents is shown in the following formula:

[0057]

[0058] Among them, THD k Indicates the degree of distortion of the k-order harmonic current component to the fundamental load current, k max Indicates the maximum order of harmonic current.

[0059] The load current containing the 9th-order harmonic component can be divided into two parts to solve the AC loss. The sine wave with the load current fundamental wave as the amplitude is defined as the main current fluctuation (major), and the amplitude changes formed by the peaks and valleys of other parts are defined as minor current fluctuations (minor). The AC loss Q of multi-order harmonic current should be the sum of the hysteresis loss generated by the main current fluctuation and the minor current fluctuation. The calculation formula is as follows:

[0060]

[0061] Among them, Q major Hysteresis losses caused by main current fluctuations, To represent the hysteresis loss caused by the i-th small current fluctuation, The self-field transmission hysteresis loss caused by the main current fluctuation, is the self-field transmission hysteresis loss caused by small current fluctuations, Q mag The external field transmission hysteresis loss generated by the current, including the external field transmission hysteresis loss caused by the main current fluctuation and external field transmission hysteresis loss caused by small current fluctuations

[0062] Self-field transmission hysteresis loss caused by main current fluctuation The calculation formula is as follows:

[0063]

[0064] i i =I major / I c

[0065] Where f is the operating frequency, N j is the number of superconducting tapes in the jth layer, μ0 is the vacuum permeability, i i Is the main current relative indicator, I major is the main current fluctuation amplitude, I c is the critical current density of the superconducting cable, and n is the total number of superconducting layers.

[0066] Self-field transmission hysteresis loss caused by small current fluctuations The calculation formula is as follows:

[0067]

[0068] i i =I minor / I c

[0069] in, is the number of the ith small current fluctuation, such as Figure 3 As shown in the figure, since the phase of the harmonic component is zero, the small current fluctuations appear symmetrically. is the self-field transmission hysteresis loss caused by the i-th small current fluctuation, i max is the number of small current types, f is the operating frequency, N j is the number of superconducting tapes in the jth layer, μ0 is the vacuum magnetic permeability, n is the total number of superconducting layers, I c is the critical current density of the superconducting cable, i i It is a relative indicator of small current, I minor It is the small current fluctuation amplitude.

[0070] Hysteresis loss Q of external field transmission generated by current mag The calculation formula is as follows:

[0071] Q mag =∑Q magi

[0072]

[0073] Among them, Q magi is the external field magnetization loss of the i-th superconducting tape, B i is the magnetic induction intensity at the i-th layer of superconducting cable, β iis the relative index of magnetic induction, S i is the cross-sectional area of ​​the i-th layer of superconducting tape, B zi and B θi are the axial magnetic field generated by the i-th layer of toroidal current inside the i-th layer and the toroidal magnetic field generated by the i-th layer of axial current outside the i-th layer, respectively. C is the critical current of the superconducting tape under the action of the magnetic field, and b is half of the thickness of the superconducting cable tape.

[0074] In solving the axial magnetic field B generated by the i-th layer of circular current inside the i-th layer zi and the toroidal magnetic field B generated by the axial current of the i-th layer outside the i-th layer θi When the main current fluctuation amplitude I major Instead of solving the current value of each layer, the calculation formula is as follows:

[0075]

[0076] Among them, ε k is the relative dielectric medium, L pk and L pi is the winding pitch, r ic and r io are the inner radius and outer radius of the i-th current-carrying layer respectively.

[0077] Taking the load current containing the 9th order harmonic component with THD=0.1 and phase 0 as an example, the AC loss of phase A of the three-phase turnkey superconducting cable is calculated. The expression of this load current is shown as follows:

[0078] I A (t)=2200sin(ωt)+220sin(9ωt)

[0079] The current distribution of the load current in the multilayer superconducting cable is:

[0080] I A1 =984.11sin(ωt)+98.411sin(9ωt)

[0081] I A2 =1215.9sin(ωt)+121.589sin(9ωt)

[0082] I S1 =-1078.2sin(ωt)-107.8202sin(9ωt)

[0083] I S2 =-1121.8sin(ωt)-112.1798sin(9ωt)

[0084] The AC loss of multi-order harmonic components obtained from this solution is:

[0085]

[0086] S2. Calculate the AC loss of the asymmetric current component.

[0087] In an ideal three-phase power system, in order to achieve optimal power transmission and equipment operation, the three-phase voltage or current should have the same amplitude and phase difference to form a balanced system. However, in actual operation, the power system is often affected by various reasons such as asymmetric loads, asymmetric faults, harmonics, etc., resulting in amplitude differences, phase differences or waveform shapes between the three phases. The resulting degradation in power quality is also an important aspect that needs to be evaluated in power grid operation. The analysis process of unbalanced current will use the symmetrical component method to convert the asymmetric three-phase alternating current into three sets of symmetrical current vectors: positive sequence current, negative sequence current and zero sequence current. The positive sequence component represents the balanced part of the voltage or current, represented by I1, I1 = 1 / 3 (I a +aI b +a 2 I c ); The negative sequence component represents the unbalanced part of the voltage or current, represented by I2, I2 = 1 / 3 (I a +a 2 I b +aI c ); Zero sequence component refers to the part of voltage or current with a phase difference of 0 degree in the three phases, represented by I0, I0 = 1 / 3 (I a +I b +I c ). Where a represents a complex unit, a=e j120° I a ,I b ,I c Respectively represent three-phase alternating current.

[0088] The existence of negative sequence current and zero sequence current affects the balance of three-phase AC. In order to quantify the imbalance of three-phase current, the three-phase imbalance degree Unbalance is introduced:

[0089]

[0090] To study asymmetry, changing one of the three phases or changing two of the three phases at the same time has the same effect, so a single variable method is used in this embodiment for research, and the cause of asymmetry can be the current amplitude or the current phase, and for the case of harmonic components, it can also be the imbalance of harmonic current components. For power systems with voltage levels of 10kV and above, the current imbalance generally does not exceed 7%, so in the asymmetric current design, the imbalance is taken as 3%, 5%, 6%, 7%, and 10%, respectively.

[0091] The three-phase coaxial superconducting cable has a copper shielding layer outside the three-phase superconducting tape. When the cable is operating normally, the three-phase current is balanced, and the shielding layer flows with a current that is equal to the sum of the three-phase currents and in the opposite direction, so the shielding layer current is 0 during normal operation. When the three-phase current is unbalanced, the shielding layer will flow with a current that is not equal to 0 and is equal to the sum of the three-phase currents and in the opposite direction. The copper material has a much greater resistance than the superconducting material, so most of the AC loss generated at this time comes from the copper loss of the shielding layer.

[0092] Taking the A-phase current as an example, we explore the changes in AC loss when the current amplitude is unbalanced under the three-phase coaxial structure. The changes in AC loss when the A-phase amplitude is changed are as follows: Figure 4 As shown by Figure 4 It can be seen that as the A phase amplitude increases, the higher the imbalance, the higher the AC loss will be. As can be seen from the figure, as the imbalance increases, the increase in copper shielding layer loss is much greater than the increase in superconducting cable body AC loss. When the imbalance reaches 7%, the AC loss increases by about 7.9 times, of which the copper shielding layer loss accounts for about 85%, and the superconducting cable body loss increases by about 17.6%, and as the imbalance increases, the copper shielding layer loss accounts for an increasing proportion.

[0093] The change of AC loss when changing the phase of phase A is as follows Figure 5 As shown by Figure 5 It can be seen that as the phase of phase A increases, the higher the imbalance, the higher the AC loss will be. As can be seen from the figure, as the imbalance increases, the increase in copper shielding layer loss is much greater than the increase in superconducting cable body AC loss. When the imbalance reaches 7%, the AC loss increases by about 7.4 times, of which the copper shielding layer loss accounts for about 87%, and as the imbalance increases, the proportion of copper shielding layer loss increases. Unlike changing the amplitude, when changing the phase, the superconducting cable body loss hardly changes as the imbalance increases.

[0094] S3. Calculate the AC loss of the terminal part.

[0095] The AC loss in the terminal part includes Joule heat loss W and leakage heat loss W ter , the calculation formulas are as follows:

[0096] W=n p I 2 R p

[0097]

[0098] Among them, n p is the number of phases of superconducting cable, R p is the single-phase terminal resistance of the superconducting cable. In this embodiment, R p=70μΩ, is the leakage heat loss, I is the single-phase current, K is the thermal conductivity, ρ is the resistivity, and T is the temperature.

[0099] The values ​​of the thermal conductivity K of copper conductors at different temperatures and the fitting function curves at different temperatures are as follows: Figure 6 As shown, the fitting function is as follows:

[0100]

[0101] The values ​​and fitting function curves of the thermal conductivity K and resistivity ρ of copper conductor at different temperatures are as follows: Figure 7 As shown, the resistivity fitting function is as follows:

[0102] ρ=-7.215×10 -16 T 3 +3.586×10 -13 T 2 +1.282×10 -11 T+2.64×10 -10

[0103] S4. Add the AC loss of the main body, the calculated AC loss of the asymmetric current component and the AC loss of the terminal part to obtain the AC loss of the three-phase all-in-one superconducting cable.

[0104] Currents of different amplitudes are introduced into the three-phase turnkey superconducting cable, with a step size of 100A. The calculation results of each component of AC loss are as follows: Figure 8 As shown in (8a), the superposition result is Figure 8 As shown in (8b). Figure 8 It can be seen that when the current is less than 1150A, the current of a single superconducting tape is very small, resulting in extremely small cable body losses. As the current increases, the terminal Joule heat loss always occupies the dominant position. When the transmission current reaches the rated current of 2300A, the terminal Joule heat loss accounts for about 60% of the total system loss.

[0105] Example 2

[0106] This embodiment provides an electronic device, including a memory and a processor, wherein the processor is used to execute a program stored in the memory, wherein the program includes a number of instructions and can execute all or part of the steps of the method described in Example 1. The memory includes a computer-readable storage medium, which can be a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and other media that can store program codes.

[0107] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for calculating AC loss of a three-phase coaxial superconducting cable, characterized in that: The following steps are involved: Calculating the AC loss of the main body, wherein the AC loss of the main body includes AC losses of multiple harmonic components solved by an analytical method; Calculate the AC losses of asymmetrical current components; Calculating the AC loss of the terminal part, wherein the AC loss of the terminal part includes Joule heat loss and leakage heat loss; adding the AC loss of the main body part, the AC loss of the asymmetric current component and the AC loss of the terminal part to obtain the AC loss of the three-phase coaxial superconducting cable; Among them, the multi-order harmonic component AC loss includes hysteresis loss caused by main current fluctuations and hysteresis loss caused by multiple small current fluctuations. The main current fluctuation is a sine wave with the fundamental wave of the load current as the amplitude. The small current fluctuation is current fluctuation caused by harmonic current distortion. The harmonic current is obtained by the interlayer current distribution solution method.

2. A method for calculating AC loss of a three-phase turnkey superconducting cable according to claim 1, characterized in that: The calculation formula of the AC loss of the multi-order harmonic components is as follows: Among them, Q is the AC loss of multi-order harmonic components, Q major Hysteresis losses caused by main current fluctuations, To represent the hysteresis loss caused by the i-th small current fluctuation, The self-field transmission hysteresis loss caused by the main current fluctuation, is the self-field transmission hysteresis loss caused by small current fluctuations, Q mag The external field transmission hysteresis loss generated by the current, including the external field transmission hysteresis loss caused by the main current fluctuation and external field transmission hysteresis loss caused by small current fluctuations 3. A method for calculating AC loss of a three-phase turnkey superconducting cable according to claim 2, characterized in that: Self-field transmission hysteresis loss caused by main current fluctuation The calculation formula is as follows: i i =I major / I c Where f is the operating frequency, N j is the number of superconducting tapes in the jth layer, μ0 is the vacuum permeability, i i Is the main current relative indicator, I major is the main current fluctuation amplitude, I c is the critical current density of the superconducting cable, and n is the total number of superconducting layers.

4. A method for calculating AC loss of a three-phase turnkey superconducting cable according to claim 2, characterized in that: Self-field transmission hysteresis loss caused by small current fluctuations The calculation formula is as follows: i i =I minor / I c in, is the number of the ith small current fluctuation, is the self-field transmission hysteresis loss caused by the i-th small current fluctuation, i max is the number of small current types, f is the operating frequency, N j is the number of superconducting tapes in the jth layer, μ0 is the vacuum magnetic permeability, n is the total number of superconducting layers, I c is the critical current density of the superconducting cable, i i It is a relative indicator of small current, I minor It is the small current fluctuation amplitude.

5. The method for calculating AC loss of a three-phase turnkey superconducting cable according to claim 2, characterized in that: The calculation formula of the external field transmission hysteresis loss Qmag generated by the current is as follows: Among them, Q magi is the external field magnetization loss of the i-th layer of superconducting tape, f is the operating frequency, B i is the magnetic induction intensity at the i-th layer of superconducting cable, β i is the relative index of magnetic induction, S i is the cross-sectional area of ​​the i-th layer of superconducting tape, B zi and B θi are the axial magnetic field generated by the i-th layer of toroidal current inside the i-th layer and the toroidal magnetic field generated by the i-th layer of axial current outside the i-th layer, respectively. C is the critical current of the superconducting tape under the action of the magnetic field, μ0 is the magnetic permeability of the vacuum, and b is half the thickness of the superconducting cable tape.

6. A method for calculating AC loss of a three-phase turnkey superconducting cable according to claim 5, characterized in that: In solving the axial magnetic field B generated by the i-th layer of circular current inside the i-th layer zi and the toroidal magnetic field B generated by the axial current of the i-th layer outside the i-th layer θi When the main current fluctuation amplitude I major Instead of solving the current value of each layer, the calculation formula is as follows: Where n is the total number of superconducting layers, ε k is the relative dielectric medium, L pk and L pi is the winding pitch, r ic and r io are the inner radius and outer radius of the i-th current-carrying layer respectively.

7. The method for calculating AC loss of a three-phase turnkey superconducting cable according to claim 1, characterized in that: The asymmetric current component AC loss includes shielding layer copper loss.

8. The method for calculating AC loss of a three-phase turnkey superconducting cable according to claim 1, characterized in that: The calculation formula of the Joule heat loss is as follows: W=n p I 2 R p Where W is the Joule heat loss, n p is the number of phases of the superconducting cable, I is the single-phase current, R p It is the single-phase terminal resistance of the superconducting cable; The calculation formula of the heat leakage loss is as follows: Among them, W ter is the heat leakage loss, K is the thermal conductivity, ρ is the resistivity, and T is the temperature.

9. The method for calculating AC loss of a three-phase turnkey superconducting cable according to claim 1, characterized in that: The specific steps of the interlayer current distribution solution method are as follows: Construct the equivalent circuit diagram of multi-layer superconducting cable, write the Kirchhoff voltage equation of each phase and each layer for each order current containing harmonic components, and combine them to obtain the Kirchhoff voltage equation matrix; According to the Kirchhoff voltage equation matrix, the voltage of each phase is solved by using the current relationship between each phase current and the conductive layer and the shielding layer, and the current distribution of each layer is solved by using the same voltage of each layer in each phase.

10. An electronic device comprising a memory, a processor, and a program stored in the memory, characterized in that: When the processor executes the program, the method according to any one of claims 1 to 9 is implemented.

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