Resistance-type high-temperature superconducting current limiter simulation model building method and simulation system

Abstract

The invention discloses a resistance-type high-temperature superconducting current limiter simulation model building method, which is used for carrying out analogue simulation on a resistance-type superconducting current limiter made of YBCO (Yttrium Barium Copper Oxide) superconducting tape, and comprises the following steps: S1, building an electrical model module of the resistance-type superconducting current limiter; s2, building a thermodynamic model module of the resistance type superconducting current limiter; s3, carrying out iterative circulation on the electrical model module and the thermodynamic model module; and S4, packaging the electrical model module, the thermodynamic model module and the oscilloscope reading module to obtain a resistance-type superconducting current limiter simulation model so as to access a power grid model. According to the invention, analogue simulation of the resistance-type high-temperature superconducting current limiter can be realized, and the resistance-type high-temperature superconducting current limiter can be connected into a simulation power grid for testing.

Description

Technical Field

[0001] The present invention relates to the field of superconducting fault current limiters, and particularly to a method for building a simulation model and a simulation system of a resistive high-temperature superconducting fault current limiter. Background Art

[0002] A superconducting material refers to a material whose resistance is equal to zero and through which magnetic lines of force cannot pass when temperature, magnetic field and current density meet certain conditions. To maintain the superconducting state of a superconducting material, it is necessary to keep it operating within three interrelated critical conditions, including critical current, critical temperature and critical magnetic field. Once a superconducting material exceeds any one of these critical conditions, it will transition from the superconducting state to the normal state.

[0003] As a new type of current limiting device, the resistive superconducting fault current limiter (RSFCL) has become a widely used type of superconducting fault current limiter in the power system due to its simple structure and operating characteristics. It utilizes the high-resistance characteristic of high-temperature superconducting materials in the normal state to effectively limit fault current, thereby preventing problems such as overload and equipment damage in the power system, and providing an important guarantee for the safe and stable operation of the power grid.

[0004] To realize the engineering application of RSFCL in the power grid, it is necessary to simulate it during the power grid design stage to lay a foundation for actual installation and application. Chinese Patent CN 105160047 A discloses a digital modeling and simulation method of a resistive superconducting fault current limiter based on YBCO superconducting tapes. According to the circuit model of the resistive superconducting fault current limiter, it calculates the line current and the current of the superconducting tape to achieve the simulation calculation of the resistive superconducting fault current limiter. This method uses a simple piecewise function fitting form for the calculation of the superconducting layer resistance, only considering the superconducting state when the temperature is higher or lower than the critical temperature, without considering the coupling relationship between the heat / temperature change per unit time and the performance of the superconducting material at the thermodynamic and electrical levels, nor considering the changes in the critical temperature and critical current of the superconducting material, and thus cannot accurately simulate the operating state of RSFCL in the power grid, making it difficult to achieve accurate engineering simulation of RSFCL in the power grid. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for building a simulation model and a simulation system of a resistive high-temperature superconducting fault current limiter.

[0006] A technical solution for achieving the above purpose is: a method for building a simulation model of a resistive high-temperature superconducting fault current limiter, used for simulating a resistive superconducting fault current limiter made of YBCO superconducting tapes, characterized by including the following steps:

[0007] S1, building an electrical model module of the resistive superconducting fault current limiter;

[0008] S2. Build a thermodynamic model module for the resistive superconducting fault current limiter;

[0009] S3. Iteratively loop the electrical model module and the thermodynamic model module;

[0010] S4. Package the electrical model module, the thermodynamic model module, and the oscilloscope reading module to obtain a simulation model of the resistive superconducting fault current limiter for connection to the power grid model.

[0011] Preferably, in S1, the equivalent circuit of the electrical model module of the resistive superconducting fault current limiter made of YBCO superconducting tape consists of three parallel resistors, namely R s , R c , and R p , where R s is the resistance of the superconducting layer; R c is the resistance of the wrapping layer outside the superconducting layer, which is a linear resistor varying with temperature; R p is a parallel resistor, a shunt resistor incorporated to prevent excessive heating during overcurrent timeout.

[0012] Preferably, for R s , the critical current of the superconducting layer is:

[0013]

[0014] where, I C0 is the critical current of the superconducting layer at the initial moment, I CT is the critical current of the superconducting tape at the current moment, T is the current temperature of the superconducting tape, and T C is the critical temperature of the superconducting tape;

[0015] The unit voltage across the superconducting layer in the superconducting state is:

[0016]

[0017] where: for the resistive superconducting fault current limiter made of YBCO superconducting tape, the exp value is 15 - 30; U c is the critical voltage; I is the real-time current on the superconducting tape;

[0018] During the quench process of the conductor, it continuously exchanges heat with the outside world. When the temperature rises above the critical temperature, the superconductor turns into the normal state, and the voltage across its two ends varies with temperature. The unit voltage across the superconducting layer is a curve related to temperature, specifically:

[0019]

[0020] where: ρ TC is the resistivity of the superconducting layer; J is the current density of the superconducting tape;

[0021] If it is detected that the current at a certain moment has become less than the critical current while the temperature on the superconducting tape is still higher than the critical temperature, it indicates that the superconductor is still in the normal state, and the voltage is still calculated according to the above formula;

[0022] Thus, R s The voltage across the two ends at any moment, and the resistance value of Rs at any moment is:

[0023]

[0024] where: L is the length of the superconducting tape;

[0025] For R c , the sheath resistance is a linear resistance that varies with temperature, and the specific calculation is:

[0026] ρ = ρ0(1 + αT) (5)

[0027] In the formula, ρ is the resistivity of the sheath material at temperature T, α is the temperature coefficient of the material resistance, and T is the current ambient temperature;

[0028] The expression of the linear resistance R c is:

[0029]

[0030] In the formula, l, w, and h represent the length, width, and thickness of the sheath respectively;

[0031] For R p , the parallel resistance R p is a fixed-value resistance that plays a shunting role. This resistance is not encapsulated with the superconducting tape in the current limiter, and its temperature remains almost unchanged. The resistance value of R p is a fixed value during operation;

[0032] Furthermore, the superconducting layer resistance R S and the copper layer resistance R C These two resistances are connected in parallel and equivalent to a resistance R SC . The external characteristics of the entire superconducting current limiter are composed of the equivalent superconducting tape resistance R SC and the parallel resistance R P connected in parallel and calculated.

[0033] Preferably, in S2, in the thermodynamic model module of the resistive superconducting current limiter made of YBCO superconducting tape, the temperature is calculated as follows:

[0034] Q1 = UIΔt (7)

[0035] Q2 = λ(T - T0)·S·Δt (8)

[0036]

[0037] Wherein: Q1 is the heat generated by the superconducting tape during the period from t1 to t2, U and I are the voltage and current on the superconducting tape respectively, and Δt is the time interval; Q2 is the heat dissipated by the superconducting tape during this period, T is the real-time temperature of the superconducting tape, T0 is the initial temperature of the superconducting tape, λ is the heat transfer coefficient, and S is the surface area of the superconducting tape; m is the mass of the superconducting tape, and C is the specific heat capacity, is the temperature at time t1, is the temperature at time t2; when the value of Q1 - Q2 is positive, the temperature of the superconducting tape rises; otherwise, the temperature of the superconducting tape drops.

[0038] Preferably, in S3, the logic of iteratively cycling the electrical model module and the thermodynamic model module is specifically as follows:

[0039] S310, input the critical temperature T of the superconducting tape into the electrical model module C and the superconducting tape and the initial critical current I CT0 ;

[0040] S320, input the initial ambient temperature T0 into the thermodynamic model module, calculate the heat absorption and heat dissipation of the superconducting tape in the current state, and calculate the real-time temperature T of the superconducting tape accordingly;

[0041] S330, input the temperature into the electrical model module, and calculate the real-time critical current I CT ;

[0042] S340, the electrical model module determines the state of the superconducting fault current limiter based on the magnitude relationship between the real-time current and the real-time critical current, and the magnitude relationship between the real-time temperature and the critical temperature, and calculates the voltage across the superconducting fault current limiter accordingly;

[0043] S350, the electrical model module calculates the resistance of the superconducting layer based on the voltage across the superconducting fault current limiter, and calculates the resistance of the superconducting fault current limiter accordingly;

[0044] S360, the electrical model module feeds back the voltage, current, and resistance of the superconducting fault current limiter to the thermodynamic model module for the next heat absorption and heat dissipation calculation to achieve iteration.

[0045] Preferably, S340 specifically includes:

[0046] S341, determine whether the real-time current is greater than the real-time critical current. If it does not exceed, enter step S342; if it exceeds, enter step 343;

[0047] S342. Determine whether the real-time temperature is greater than the critical temperature. If it is greater, it is determined as the recovery process, and the voltage across the superconducting fault current limiter is calculated by Equation (2); if it is less, it is determined as being in the superconducting state, and the voltage across the superconducting fault current limiter is 0.

[0048] S343. Determine whether the real-time temperature is greater than the critical temperature. If it is less, it is determined as the quench process, and the voltage across the superconducting fault current limiter is calculated by Equation (2); if it is greater, it is determined that the superconducting fault current limiter is in the normal state, and the voltage across the superconducting fault current limiter is calculated by Equation (3).

[0049] Preferably, the oscilloscope reading module quantitatively describes the current-limiting performance of the superconducting fault current limiter. The current-limiting ratio D% of the superconducting fault current limiter is:

[0050]

[0051] where: I1 is the peak short-circuit current without the superconducting fault current limiter; I2 is the peak short-circuit current limited after installing the superconducting fault current limiter; D% is a parameter for measuring the current-limiting effect of the current limiter, and the variation range is 0 < D < 1. The larger D is, the better the current-limiting effect of the superconducting fault current limiter is.

[0052] The resistive high-temperature superconducting fault current limiter simulation system built by using the above resistive high-temperature superconducting fault current limiter simulation model building method includes an electrical model module, a thermodynamic model module, and an oscilloscope reading module; the electrical model module is connected to the thermodynamic model module and performs iterative cycles, and the two are jointly encapsulated with the oscilloscope reading module to obtain a resistive superconducting fault current limiter simulation model. The resistive high-temperature superconducting fault current limiter is connected to the actual power grid model as needed through the two ports of "+" and "-".

[0053] Preferably, the electrical model module inputs the current temperature T, the current I, the initial critical temperature T C0 and the initial critical current I CT0 , outputs the heat generation QRs of the superconducting layer, the heat generation QRc of the cladding layer, and the heat dissipation Qc of the superconducting tape to the thermodynamic model module, and outputs the equivalent resistance of the resistive superconducting fault current limiter outward.

[0054] Preferably, the thermodynamic model module inputs the heat generation QRs of the superconducting layer, the heat generation QRc of the cladding layer, and the heat dissipation Qc of the superconducting tape, and outputs the temperature T to the electrical model module.

[0055] The advantageous effects of the present invention are as follows:

[0056] 1. By establishing an electrically coupled electrical model module and thermodynamic model module, the present invention realizes the establishment of a simulation model for a resistive high-temperature superconducting fault current limiter, and can accurately describe the characteristic changes of the superconducting fault current limiter during the quench instant and the recovery process, and realizes the transient simulation of the operating state of the resistive high-temperature superconducting fault current limiter.

[0057] 2. The present invention encapsulates the electrical model module, the thermodynamic model module, and the oscilloscope reading module on the simulation platform, realizing the deviceization and standardization of the resistive high-temperature superconducting fault current limiter. It can connect different models of resistive high-temperature superconducting fault current limiters to the simulated power grid, revealing their operating mechanisms in the power system. The simulation of their dynamic performance provides a theoretical basis and simulation tool support for the subsequent application of resistive high-temperature superconducting fault current limiters in complex distribution networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 Schematic diagram of the interlayer structure of the resistive superconducting fault current limiter;

[0059] Figure 2 Schematic diagram of the equivalent circuit of the resistive superconducting fault current limiter;

[0060] Figure 3 Iterative logic flow chart of the electrical model module and the thermodynamic model module;

[0061] Figure 4 Schematic diagram of the electrical model module written using the function module;

[0062] Figure 5 Schematic diagram of the thermodynamic model module written using the function module;

[0063] Figure 6 Schematic diagram of the encapsulation of the electrical model module, the thermodynamic model module, and the oscilloscope;

[0064] Figure 7 Schematic diagram of the 10 kV line model;

[0065] Figure 8 Comparison chart of the short-circuit current magnitude before and after installing the RSFCL;

[0066] Figure 9 Temperature change diagram of the resistive high-temperature superconducting fault current limiter;

[0067] Figure 10 Resistance change diagram of the superconducting tape;

[0068] Figure 11 Current change diagram of the superconducting layer and the parallel resistor;

[0069] Figure 12 Short-circuit current magnitude change diagram under different tape lengths. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0070] In order to better understand the technical solution of the present invention, the following provides a detailed description through specific embodiments:

[0071] The physical layer of the currently mainstream resistive superconducting fault current limiter (RSFCL) made of YBCO superconducting tape is as follows Figure 1 shown, including the YBCO layer (superconducting layer) 1, the cladding layer 2 and the base tape layer 3, which can be equivalent to a circuit composed of three parallel resistors, as Figure 2 shown.

[0072] In this embodiment, a method for building a simulation model of a resistive high-temperature superconducting fault current limiter of the present invention is based on Matlab / Simulink. It is mainly divided into two parts: the electrical part and the thermodynamic part. However, these two parts are not completely independent but are coupled with each other. The specific steps are as follows:

[0073] S1. Build the electrical model module of the resistive superconducting fault current limiter.

[0074] In S1, the equivalent circuit of the electrical model module of the resistive superconducting fault current limiter made of YBCO superconducting tape is composed of three parallel resistors, namely R s , R c and R p , where R s is the resistance of the superconducting layer, that is, the pure superconducting material part, whose resistance is zero in the superconducting state, and shows a high resistance state when the current is too large and the superconductor quenches. R c is the resistance of the cladding layer outside the superconducting layer, which is a linear resistance varying with temperature. The reason for its generation is that the superconducting tape is surrounded by multiple layers of materials represented by a copper layer. The superconducting layer and the cladding layer are collectively called the superconducting tape. R p is a parallel resistor, a shunt resistor incorporated to prevent excessive heat generation during overcurrent quench. The resistance value of this resistor can be adjusted according to the actual situation.

[0075] For R s , among the three important parameters (critical current, critical temperature and critical magnetic field strength) that affect the quench of the superconductor, since the critical magnetic field strength is generally much greater than the external magnetic field strength under the working conditions, its influence is generally not considered in the modeling, and only the influence of temperature and current on the superconducting resistance state is considered.

[0076] The critical current of the superconducting layer is:

[0077]

[0078] where, I C0 is the critical current of the superconducting layer at the initial moment, I CT is the critical current of the superconducting tape at the current moment, T is the current temperature of the superconducting tape, and T C is the critical temperature of the superconducting tape.

[0079] According to the quench principle of superconductors, when a short-circuit fault occurs in the circuit and the current flowing through the superconducting tape is greater than its critical current, that is, when the current density is greater than the critical current density at this time, the superconductor enters the quench process.

[0080] The unit voltage across the superconducting layer in the superconducting state is:

[0081]

[0082] Among them: for the YBCO superconducting tape resistive superconducting fault current limiter, the exp value is 15 - 30. In this embodiment, exp = 21 is taken. U c is the critical voltage; I is the real-time current on the superconducting tape, and the units are both A.

[0083] During the quench process, the superconductor continuously exchanges heat with the outside world. When the temperature rises above the critical temperature, the superconductor turns into the normal state, and the voltage across its two ends changes with temperature. The unit voltage across the superconducting layer is a curve related to temperature, specifically:

[0084]

[0085] Among them: ρ TC is the resistivity of the superconducting layer; J is the current density of the superconducting tape;

[0086] If it is detected that the current at a certain moment is already less than the critical current, while the temperature on the superconducting tape is still higher than the critical temperature, it means that the superconductor is still in the normal state, and the voltage is still calculated according to the above formula;

[0087] From this, the R s voltage across both ends at any moment is obtained, and the resistance value of Rs at any moment is:

[0088]

[0089] Among them: L is the length of the superconducting tape, and the unit is m.

[0090] For R c , it is the resistance of the wrapping layer. This resistance is a linear resistance whose value changes with temperature and has important parameters such as resistivity at room temperature and temperature coefficient of resistance. Strictly speaking, this resistance is not only the resistance generated by the copper layer, but since its main part is copper and the experimental data shows that its temperature coefficient of resistance and resistivity are very close to those of copper resistance, the copper layer resistance is approximated in this embodiment.

[0091] The specific calculation is:

[0092] ρ = ρ0(1 + αT) (5)

[0093] Where ρ is the resistivity of the wrapping layer material at temperature T, approximated as the resistivity of copper in this embodiment, α is the temperature coefficient of material resistance, and T is the current ambient temperature.

[0094] The following parameters can be obtained by referring to relevant materials:

[0095] ρ0 = 0.0156 (Ω·mm 2 / m)

[0096] α = 0.00394 (1 / K)

[0097] ρ0 represents the resistivity of copper at 0°C, with the unit of ohm per millimeter 2 。

[0098] α represents the temperature coefficient of resistance of copper resistance, with the unit of 1 / degree Celsius or 1 / Kelvin.

[0099] The linear resistance R c has the following expression:

[0100]

[0101] Where l, w, and h represent the length, width, and thickness of the wrapping layer respectively.

[0102] For R p , the parallel resistance R p is a fixed-value resistor that serves as a shunt resistor. This resistor is not encapsulated with the superconducting tape in the current limiter, and its temperature remains almost constant. The resistance value of R p also remains basically unchanged during operation and is a fixed value.

[0103] Furthermore, the superconducting layer resistance R S and the copper layer resistance R C are paralleled and equivalent to a single resistor R SC . The external characteristics of the entire superconducting current limiter are composed of the equivalent superconducting tape resistance R SC and the parallel resistance R P in parallel and are calculated accordingly.

[0104] S2. Build a thermodynamic model module for the resistive superconducting current limiter.

[0105] To keep the temperature of the superconducting tape below the critical temperature under normal conditions, the superconducting tape operates in a liquid nitrogen environment with a temperature of 77 K, which is the initial temperature of the superconducting material. When the superconducting tape is in the superconducting state, since its own resistance is close to zero, almost no heat is generated, keeping the temperature of the superconducting tape near the initial temperature. When the current passing through the superconducting fault current limiter increases and exceeds the critical current of the superconducting tape, the superconducting tape quenches and exhibits resistance characteristics, quickly becoming a high-resistance state and generating a large amount of heat, causing the current limiter to exceed the critical temperature. At this time, there is also a heat conduction process between the superconducting tape and the surrounding liquid nitrogen, which affects the temperature rise value of the superconducting tape.

[0106] The temperature of the superconducting tape has a great influence on the electrical characteristics of the current limiter. On the one hand, the temperature affects the resistivity of the copper resistance, that is, it affects the linear resistance part; on the other hand, the change in temperature has a significant impact on the magnitude of the critical current of the superconducting tape, thus affecting the equivalent resistance of the superconducting resistance layer. Therefore, it is necessary to gradually calculate the temperature characteristics of the current limiter at each moment.

[0107] The calculation process of the temperature is as follows: Equation (7) is used to calculate the heat generated by the superconducting tape, Equation (8) is used to calculate the heat dissipated by the superconducting tape, and Equation (9) calculates the change in the temperature of the superconducting tape based on the heat generation and heat dissipation of the superconducting tape.

[0108] Q1 = UIΔt (7)

[0109] Q2 = λ(T - T0)·S·Δt (8)

[0110]

[0111] Where:

[0112] Q1 is the heat generated by the superconducting tape during the time period from t1 to t2, with the unit of joule.

[0113] Q2 is the heat dissipated by the superconducting tape during this time period, with the unit of joule.

[0114] U and I are the voltage and current on the superconducting tape respectively.

[0115] Δt is the time interval.

[0116] T is the real-time temperature of the superconducting tape, with the unit of Kelvin; T0 is the initial temperature of the superconducting tape, with the unit of Kelvin; λ is the heat transfer coefficient, S is the surface area of the superconducting tape, with the unit of square millimeter; m is the mass of the superconducting tape, with the unit of kilogram; C is the specific heat capacity, with the unit of joule per kilogram degree.

[0117] is the temperature at time t1, is the temperature at time t2, and the unit is Kelvin. When the value of Q1 - Q2 is positive, the temperature of the superconducting tape increases; conversely, the temperature of the superconducting tape decreases.

[0118] S3. Iteratively loop the electrical model module and the thermodynamic model module. Obtain the operation logic of the electrical simulation model of the resistive high-temperature superconducting fault current limiter, specifically:

[0119] S310. Input the critical temperature T of the superconducting tape into the electrical model module C and the initial critical current I of the superconducting tape CT0 ;

[0120] S320. Input the initial ambient temperature T0 into the thermodynamic model module, calculate the heat absorption and heat dissipation of the superconducting tape in the current state, and calculate the real-time temperature T of the superconducting tape accordingly;

[0121] S330. Input the temperature into the electrical model module and calculate the real-time critical current I CT ;

[0122] S340. The electrical model module judges the state of the superconducting fault current limiter according to the magnitude relationship between the real-time current and the real-time critical current, and the magnitude relationship between the real-time temperature and the critical temperature, and calculates the voltage across the superconducting fault current limiter accordingly;

[0123] S350. The electrical model module calculates the resistance of the superconducting layer according to the voltage across the superconducting fault current limiter, and calculates the resistance of the superconducting fault current limiter accordingly;

[0124] S360. The electrical model module feeds back the voltage, current, and resistance of the superconducting fault current limiter to the thermodynamic model module for the next heat absorption and heat dissipation calculation to achieve iteration.

[0125] S340 specifically includes:

[0126] S341. Judge whether the real-time current is greater than the real-time critical current. If it does not exceed, enter step S342; if it exceeds, enter step 343;

[0127] S342. Judge whether the real-time temperature is greater than the critical temperature. If it is greater, it is determined to be the recovery process, and the voltage across the superconducting fault current limiter is calculated by Equation (2); if it is less, it is determined to be in the superconducting state, and the voltage across the superconducting fault current limiter is 0;

[0128] S343. Judge whether the real-time temperature is greater than the critical temperature. If it is less, it is determined to be the quench process, and the voltage across the superconducting fault current limiter is calculated by Equation (2); if it is greater, it is determined that the superconducting fault current limiter is in the normal state, and the voltage across the superconducting fault current limiter is calculated by Equation (3).

[0129] The logic flow is as Figure 3 shown.

[0130] S4. Package the electrical model module, the thermodynamic model module, and the oscilloscope reading module to obtain a simulation model of the resistive superconducting fault current limiter for connection to the power grid model.

[0131] To quantitatively describe the current-limiting performance of the superconducting fault current limiter, the current-limiting ratio is generally used as an index to quantitatively characterize its current-limiting performance. The current-limiting ratio D% of the superconducting fault current limiter is defined as:

[0132]

[0133] Where:

[0134] I1 is the peak short-circuit current (A) without the superconducting fault current limiter;

[0135] I2 is the peak short-circuit current (A) limited after installing the superconducting fault current limiter.

[0136] D% is a parameter to measure the current-limiting effect of the current limiter, and its range of variation is 0 < D < 1. The larger D is, the better the current-limiting effect of the superconducting fault current limiter. In addition, the oscilloscope is used to read other performance parameters on the RSFCL.

[0137] According to the above logic, in the Simulink environment, the electrical model and the thermodynamic model of the RSFCL are packaged together, and the working characteristics of the superconducting fault current limiter are simulated by directly controlling the resistance value of the variable resistor through an S-function module. The construction of the resistive high-temperature superconducting fault current limiter simulation system is as follows.

[0138] As Figure 4 shown, it is the electrical simulation diagram corresponding to the electrical model module of the RSFCL. The function module is used to write code to calculate the resistance values of R Figure 2 respectively to implement the electrical calculation of the RSFCL. R S R C . R P is optimized and determined according to the actual situation of the distribution network.

[0139] As Figure 5 shown, it is the thermodynamic model module of the RSFCL. Some input quantities of this module, QRs (superconducting tape heating), QRc (copper layer heating), and Qc (superconducting tape heat dissipation), are the results of electrical calculations. The input port l can set the tape length of a single current limiter in meters. By adjusting the tape length of the current limiter, the resistance of the RSFCL can be changed, thereby realizing the control of the current magnitude.

[0140] The output quantity T calculated by the thermodynamic model module is temperature, and the next cycle is carried out through the Memory module. The entire RSFCL electrical simulation model is to iterate and loop the above two modules to calculate its external port characteristics.

[0141] The electrical model, thermodynamic model, and oscilloscope reading module are encapsulated as a whole to obtain the model as shown in Figure 6 the figure. Among them, the two ports of “+” and “-” can be connected to the actual simulation model as needed, so as to connect the RSFCL to the actual power grid.

[0142] To verify the correctness of the electrical simulation model of the resistive superconducting fault current limiter established in this study, in the following embodiment, the simplest 10kV system is taken as an example, and the RSFCL is used for simulation calculation analysis and comparison.

[0143] As shown in Figure 7 the figure, a simple 10kV line model is built on the Matlab / Simulink simulation platform to simulate typical faults and monitor and analyze the electrical characteristics of the fault current limiter. The entire simulation duration is set to 1s, the fault is set to occur at 0.02s, the fault disappearance time is 0.1s, and the fault type is a three-phase short circuit at point k. The length of the RSFCL tape used is set to 150m, the critical current is 400A (the critical current of a single superconducting tape is 200A, and two superconducting tapes are used in parallel in the example), and the parallel resistance is 5 ohms. The RSFCL model is connected to phase A, and an oscilloscope is used to measure the current flowing through the phase A line before and after installing the RSFCL at the same time. To facilitate the comparison of the results of the RSFCL limiting current, the current waveforms in the simulation time of 0 - 0.08s are selected for display, as shown in Figure 8 the figure.

[0144] Since the evaluation of the current limiting effect of the RSFCL generally focuses on the peak value of the current in the first cycle after the short circuit, it can be seen from Figure 8 the figure that when the RSFCL is not installed, the peak value of the current in the first cycle after the short circuit is 2361A; after the RSFCL is installed, the peak value of the current in the first cycle after the short circuit is reduced to 1668A, and the current limiting ratio is 29.4%. It takes about 2ms for the RSFCL to lose its superconductivity and enter the normal impedance state from the superconducting state, which conforms to the general characteristics of the RSFCL.

[0145] To further observe the process of the superconducting tape recovering to the superconducting state after the fault is removed, as shown in Figure 9, the simulation time of 0 to -1.5 s is selected, showing the whole process of the RSFCL from the occurrence of the fault leading to quench to the recovery of the superconducting state after the fault is cleared. After the fault occurs in the RSFCL at 0.02 s, the temperature rises rapidly and enters the quench state; after the fault is cleared at 0.05 s, the temperature drops slowly, and it takes about 1.2 s for the temperature to return to the initial temperature of 77 K, and the RSFCL returns to the superconducting state again. The simulation waveform is consistent with the theoretical analysis, verifying the effectiveness of the established simulation model.

[0146] As Figure 10 shows the change in the resistance R of the superconducting tape in the simulation SC . It can be seen that the resistance of the superconducting layer suddenly increases at 0.02 s, but the overall resistance of the RSFCL is limited by the parallel resistance R P . After the fault disappears, the resistance of the superconducting layer drops rapidly and becomes 0 after a certain time, which is in line with the theoretical analysis.

[0147] As Figure 11 shows the change in the current of the superconducting tape layer and the parallel resistance layer in the simulation. It can be seen that when the superconducting tape layer is in the superconducting state, since the resistance of the superconducting tape layer is 0, almost all the current flows through the superconducting tape layer; when the superconducting tape layer is in the quench state, the parallel resistance layer shunts most of the current to ensure that the superconducting tape layer is not burned due to excessive current.

[0148] To further illustrate the influence of the superconducting tape length on the current-limiting effect, the tape length is changed multiple times in the simulation to observe the current-limiting effect. Figure 12 shows the change in the short-circuit current when the superconducting tape length ranges from 100 m to 200 m (simulation tests are taken at every 10 m). From Figure 12 it can be seen that the current-limiting effect of the RSFCL is closely related to the superconducting tape length. Within a certain length range, there is a positive correlation between the tape length and the current-limiting effect.

[0149] In summary, the established RSFCL simulation model presents the relevant performance that the RSFCL can quickly enter the current-limiting mode in the fault state, can significantly suppress the fault current, and the current-limiting effect is related to parameters such as the tape length; the established RSFCL simulation model can reflect the whole process of the RSFCL from quench after the fault to the recovery of the superconducting state after the fault is cleared. It can be seen in the simulation that the response speed of the RSFCL is in the millisecond level, providing a basis for using the RSFCL for current limiting. In addition, it can be seen in the simulation that the change of the RSFCL state can be achieved without any external equipment, proving that the RSFCL is simple to operate and has certain advantages in using the RSFCL for current limiting in the distribution network.

[0150] Those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. As long as they are within the scope of the spirit of the present invention, changes and modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for building a simulation model of a resistive high-temperature superconducting fault current limiter, which is used to simulate a resistive superconducting fault current limiter made of YBCO superconducting tapes, is characterized in that, It includes the following steps: S1. Build the electrical model module of the resistive superconducting fault current limiter; S2. Build the thermodynamic model module of the resistive superconducting fault current limiter; S3. Iteratively loop the electrical model module and the thermodynamic model module; S4. Package the electrical model module, the thermodynamic model module and the oscilloscope reading module to obtain the simulation model of the resistive superconducting fault current limiter for connecting to the power grid model.

2. A method for building a simulation model of a resistive high-temperature superconducting fault current limiter according to claim 1, characterized in that In S1, the equivalent circuit of the electrical model module of the resistive superconducting fault current limiter made of YBCO superconducting tape consists of three parallel resistors, namely R s , R c and R p . Among them, R s is the resistance of the superconducting layer; R c is the resistance of the wrapping layer outside the superconducting layer, which is a linear resistor varying with temperature; R p is a parallel resistor, a shunt resistor incorporated to prevent excessive heating during overcurrent timeout.

3. The method for building a simulation model of a resistive high-temperature superconducting fault current limiter according to claim 2, wherein For R s , the critical current of the superconducting layer is: Among them, I C0 is the critical current of the superconducting layer at the initial moment, and I CT is the critical current of the superconducting tape at the current moment, T is the current temperature of the superconducting tape, and T C is the critical temperature of the superconducting tape; The unit voltage across the superconducting layer in the superconducting state is: Among them: for the YBCO superconducting tape resistive superconducting fault current limiter, the exp value is 15 - 30; U c is the critical voltage; is the real-time current on the superconducting tape; During the quench process of the conductor, it continuously exchanges heat with the outside world. When the temperature rises above the critical temperature, the superconductor turns into the normal state, and the voltage across it changes with temperature. The unit voltage across the superconducting layer is a curve related to temperature, specifically: Where: ρ TC is the resistivity of the superconducting layer; J is the current density of the superconducting tape; If it is detected that the current at a certain moment is less than the critical current, and the temperature on the superconducting tape is still higher than the critical temperature, it means that the superconductor is still in the normal state, and the voltage is still calculated according to the above formula; Thus, R is obtained. s For the voltage across both ends at any moment, the resistance value of Rs at any moment is: where: L is the length of the superconducting tape; For R c , the resistance of the wrapping layer is a linear resistance that varies with temperature, and the specific calculation is as follows: ρ = ρ0(1 + αT) (5) In the formula, ρ is the resistivity of the cladding material at temperature T, α is the temperature coefficient of material resistance, and T is the current ambient temperature; Linear resistor R c The expression is as follows: In the formula, l, w, and h represent the length, width, and thickness of the cladding respectively; For R p , the parallel resistor R p is a fixed-value resistor for current shunting. This resistor is not packaged with the superconducting tape in the current limiter, and its temperature remains almost constant. The resistance value of R p is a fixed value during operation; Further, the resistance R of the superconducting layer S and the resistance R of the copper layer C are connected in parallel and equivalent to a resistance R SC . The external characteristics of the entire superconducting current limiter are composed of the equivalent resistance R of the superconducting strip SC and the parallel resistance R P connected in parallel and calculated.

4. A method for building a simulation model of a resistive high-temperature superconducting fault current limiter according to claim 1, characterized in that, In S2, in the thermodynamic model module of the resistive superconducting fault current limiter made of YBCO superconducting tape, the temperature is calculated as follows: Q1 = UIΔt (7) Q2 = λ(T - T0)·S·Δt (8) Where: Q1 is the heat generated by the superconducting tape during the time period from t1 to t2, U and I are the voltage and current on the superconducting tape respectively, and Δt is the time interval; Q2 is the heat dissipated by the superconducting tape during this time period, T is the real-time temperature of the superconducting tape, T0 is the initial temperature of the superconducting tape, λ is the heat transfer coefficient, and S is the surface area of the superconducting tape; m is the mass of the superconducting tape, and C is the specific heat capacity. is the temperature at time t1, is the temperature at time t2; when the value of Q1 - Q2 is positive, the temperature of the superconducting tape increases; conversely, the temperature of the superconducting tape decreases.

5. A method for building a simulation model of a resistive high-temperature superconducting fault current limiter according to claim 1, characterized in that, In S3, the logic of iteratively looping the electrical model module and the thermodynamic model module is specifically: S310, input the critical temperature T of the superconducting tape in the electrical model module C and the initial critical current I of the superconducting tape CT0 ; S320. Input the initial ambient temperature T0 into the thermodynamic model module, calculate the heat absorption and heat dissipation of the superconducting tape in the current state, and calculate the real-time temperature T of the superconducting tape accordingly; S330, Input the temperature into the electrical model module and calculate the real-time critical current I CT ; S340. The electrical model module judges the state of the superconducting fault current limiter according to the magnitude relationship between the real-time current and the real-time critical current, and the magnitude relationship between the real-time temperature and the critical temperature, and calculates the voltage across the superconducting fault current limiter accordingly; S350. The electrical model module calculates the resistance of the superconducting layer according to the voltage across the superconducting fault current limiter, and calculates the resistance of the superconducting fault current limiter accordingly; S360. The electrical model module feeds back the voltage, current and resistance of the superconducting fault current limiter to the thermodynamic model module for the next heat absorption and heat dissipation calculation to achieve iteration.

6. A method for building a simulation model of a resistive high-temperature superconducting fault current limiter according to claim 5, characterized in that, S340 specifically includes: S341. Judge whether the real-time current is greater than the real-time critical current. If it does not exceed, go to step S342; if it exceeds, go to step 343; S342. Judge whether the real-time temperature is greater than the critical temperature. If it is greater, it is judged as the recovery process, and the voltage across the superconducting fault current limiter is calculated by formula (2); if it is less, it is judged as being in the superconducting state, and the voltage across the superconducting fault current limiter is 0; S343. Judge whether the real-time temperature is greater than the critical temperature. If it is less, it is judged as the quench process, and the voltage across the superconducting fault current limiter is calculated by formula (2); if it is greater, it is judged that the superconducting fault current limiter is in the normal state, and the voltage across the superconducting fault current limiter is calculated by formula (3).

7. A method for building a simulation model of a resistive high-temperature superconducting fault current limiter according to claim 1, characterized in that, The oscilloscope reading module quantitatively describes the current-limiting performance of the superconducting fault current limiter through the current-limiting ratio. The current-limiting ratio D% of the superconducting fault current limiter is: Where: I1 is the peak short-circuit current without a superconducting fault current limiter; I2 is the peak short-circuit current limited after installing the superconducting fault current limiter; D% is a parameter to measure the current-limiting effect of the fault current limiter, and the variation range is 0 < D < 1.

8. The resistive high-temperature superconducting fault current limiter simulation system built by using any one of claims 1 to 7, characterized in that, It includes an electrical model module, a thermodynamic model module, and an oscilloscope reading module; the electrical model module and the thermodynamic model module are connected to each other and perform iterative cycles. The two are jointly encapsulated with the oscilloscope reading module to obtain a resistive superconducting fault current limiter simulation model. The resistive high-temperature superconducting fault current limiter is connected to the actual power grid model as needed through two ports of "+" and "-".

9. A resistive high-temperature superconducting fault current limiter simulation system according to claim 8, characterized in that, The electrical model module inputs the current temperature T, the current I, the initial critical temperature T C0 and the initial critical current I CT0 , outputs the heat generation QRs of the superconducting layer, the heat generation QRc of the cladding layer, and the heat dissipation Qc of the superconducting tape to the thermodynamic model module, and outputs the equivalent resistance of the resistive superconducting fault current limiter externally.

10. A simulation system for a resistive high-temperature superconducting fault current limiter according to claim 9, characterized in that, The thermodynamic model module inputs the heat generation QRs of the superconducting layer, the heat generation QRc of the cladding layer, and the heat dissipation Qc of the superconducting tape, and outputs the temperature T to the electrical model module.

Images