Test Method and System for Dynamic Stability Current Sharing Test of High-Capacity Dry-Type Air Core Reactors

Abstract

A dynamic stability current sharing test method and system for a large-capacity dry-type air-core reactor. By constructing a multi-layer test package group of large-capacity dry-type air-core reactors for testing; determining dynamic and thermal stability test equipment; using voltage and current sensors to conduct N tests on the encapsulated test samples, and collecting a total of N groups of test data; minimizing the difference between the measured current value and the estimated current value in each group of test data; based on the difference, calculating the equivalent resistance and equivalent inductance of the corresponding encapsulated test sample in the test; calculating the active and reactive components according to the equivalent resistance and equivalent inductance; calculating the corresponding parallel equivalent resistance, parallel equivalent inductance, parallel active component and parallel reactive component, and calculating the relative deviation from the estimated value. If it is lower than the threshold, the uniformity meets the requirements. The present invention can realize the acquisition of uniform current among different encapsulated coils, providing data support for analyzing the heat generation situation inside the encapsulation.

Description

Technical Field

[0001] The present invention belongs to the technical field of current uniformity of air-core reactors, and particularly relates to a dynamic stability current sharing test method and system for large-capacity dry-type air-core reactors. Background Art

[0002] In the 500 kV receiving-end power grid in East China of our country, due to the dense grid structure and concentrated load, the short-circuit current in hub substations generally exceeds the breaking capacity of circuit breakers. Although traditional methods such as line breaking and bus splitting can reduce the short-circuit current, they will damage the integrity of the power grid and lead to a decline in power supply reliability. Series current-limiting reactors are connected in series to the 500 kV bus or outgoing line. By utilizing the inductive impedance characteristics, the short-circuit current can be limited to the range allowed by the circuit breaker during a fault, while maintaining the full connection operation of the main loop network and avoiding grid fragmentation. Therefore, connecting series current-limiting reactors has become the core means for short-circuit current control in the 500 kV power grid.

[0003] The 500 kV series current-limiting reactor adopts a multi-packet parallel structure with a high rated capacity and large current, which results in a large deviation in the inductance of each winding during rated operation, leading to uneven current distribution. Generally, it is necessary to optimize winding transposition and current sharing reactance compensation, and conduct dynamic and thermal stability tests under power frequency conditions to indirectly ensure that the current uniformity between packets meets the engineering requirements. In order to ensure the dynamic stability performance of the reactor under the short-circuit peak current, in the conventional scheme, it is necessary to conduct dozens of high-capacity power frequency voltage tests on the scaled-down model of the reactor. If there is no obvious abnormality in the packet after operation, it means the test passes.

[0004] However, the design complexity of the latest 500 kV series current-limiting reactor has increased significantly, the overall size and the number of packet layers have increased, the rated capacity has reached the GVar level, and the number of packet layers is as high as 30 layers. Although the conventional scheme can control the overall performance, it can only indirectly ensure the current uniformity between packets, lacking the actual measurement verification of the internal parameters and heat generation uniformity of each packet. At the same time, due to the large number of packets of the large series current-limiting reactor, the space at the star connection of its windings is relatively narrow, and only small-current measurements can be carried out. Under approximate rated conditions, the current in the 500 kV series current-limiting reactor can reach dozens of kiloamperes, and the size of the corresponding current sensor increases, so the measurement layout is difficult. At the same time, the leakage inductance of the 500 kV series current-limiting reactor is extremely strong, and the mutual inductance between packet coils is cumbersome. If the internal current is inconsistent with the simulation design result under the actual operating state, although the overall external inductance has little deviation, if there are obvious overcurrent nodes inside, serious heating will damage the coil insulation and cause serious power grid operation accidents. Summary of the Invention

[0005] To address the deficiencies in the existing technology, the present invention provides a dynamic stability current-sharing test method and system for a large-capacity dry-type air-core reactor, which can accurately collect the uniformity current between different encapsulated coils without damaging the encapsulation structure, provide data support for analyzing the heating conditions in each encapsulation, and thus effectively verify the design structure of the reactor. At the same time, by combining an optimization algorithm, the calculation of resistance and inductance parameters is accurately achieved, providing a reliable basis for predicting the current parameters in each encapsulation during actual operation and ensuring the safe and stable operation of the power grid.

[0006] The present invention adopts the following technical solutions.

[0007] The present invention proposes a dynamic stability current-sharing test method for a large-capacity dry-type air-core reactor, including:

[0008] According to the large-capacity dry-type air-core reactor to be tested, construct a multi-layer encapsulated scaled-down test sample group for the large-capacity dry-type air-core reactor test, with a total of N, respectively including 1-layer encapsulation, 2-layer encapsulation,..., N-layer encapsulation; connect the dynamic and thermal stability test equipment to the test sample; connect the AC synchronous generator to the input end of the isolation transformer through a switch, and connect the output end of the isolation transformer to both ends of the test sample encapsulated winding; successively connect the 1st to Nth layer encapsulated scaled-down test samples to the output end of the isolation transformer, apply the same voltage for the test, and collect the test data;

[0009] Set the initial vectors of the resistance and inductance of the encapsulation in the corresponding test, and use the particle swarm optimization algorithm to iteratively optimize the resistance and inductance of each group of encapsulations. Take the minimization of the difference between the discrete value of the test current and the theoretical current discrete value calculated based on the iteratively optimized values of the resistance and inductance as the constraint condition for iteration. After reaching the convergence standard, obtain the final iteratively optimized values of the resistance and inductance of each group of encapsulations; use the iteratively optimized values of the resistance and inductance of the encapsulation in each group of tests as the equivalent resistance and equivalent inductance of the corresponding encapsulation in each group of tests, and combine the discrete value of the test current to calculate the active and reactive components of the encapsulation under the test voltage in each group of tests; calculate the theoretical parallel equivalent resistance, parallel equivalent inductance, parallel active component, and parallel reactive component of the encapsulation in each group, and calculate the relative deviation with the corresponding measured value respectively. If all relative deviations are lower than the threshold, the uniformity meets the requirements.

[0010] Further, the encapsulated scaled-down test sample group refers to proportionally reducing the large-capacity dry-type air-core reactor to be tested, keeping the winding connection method and wire material unchanged, and proportionally reducing the wire diameter, encapsulation thickness, coil turns, coil length, etc., to obtain an encapsulated scaled-down test sample group with different numbers of encapsulation layers.

[0011] Further, during each test, the applied test voltage is the same, and the test voltage value is determined according to the wire diameter and encapsulation layer thickness of the scaled-down test sample group.

[0012] Furthermore, during each test, the test voltage value applied to the encapsulated reduced-ratio sample group is measured by a voltage divider, and the test current value of the encapsulated reduced-ratio sample group is measured by a current transformer.

[0013] Furthermore, according to the coil parameters of each encapsulated sample group, the initial vector of the corresponding encapsulated resistance is calculated by the following formula and the initial vector of the inductance :

[0014] ;

[0015] ;

[0016] where D is the coil diameter, H is the coil height, ρ is the resistivity of the coil, L is the coil length, and S is the cross-sectional area of the coil.

[0017] Furthermore, for each encapsulated reduced-ratio sample group, based on the initial optimization parameters , the particle swarm optimization method is adopted, and the optimization equation is:

[0018] ;

[0019] where the superscripts k and k + 1 are the discrete moments of the particle running process during the particle swarm optimization of the nth group of test data, k is an integer, k = 1, 2, 3...K, and are the velocities of the particle at the kth and (k + 1)th moments of the particle running process respectively, w is the inertia weight, is the individual optimal position of the particle at the kth moment of the particle running process, is the global optimal position of the particle at the kth moment of the particle running process, c1 and c2 are the individual learning factor and the global learning factor respectively, r1 and r2 are the individual random number and the global random number respectively, and are the positions of the particle at the kth and (k + 1)th moments of the particle running process respectively.

[0020] Furthermore, the equivalent resistance and equivalent inductance at each optimization iteration of the corresponding test are obtained by using the particle swarm optimization algorithm, and the theoretical current discrete values corresponding to the resistance and inductance iteration optimization values obtained each time are calculated by using the test voltage;

[0021] The corresponding encapsulated test current collected during the test of the encapsulated reduced-ratio sample group is discretized to obtain the test current discrete value.

[0022] Furthermore, combining the theoretical current discrete value , the constraint condition formula at the discrete moment k of the particle running process is:

[0023] ;

[0024] Among them, and are the equivalent resistance and equivalent inductance of the k-th optimization iteration corresponding to the n-th group of tests respectively, and h = 1,..., H, where H is the number of current test data sampling points. is the measured current value at the h-th moment of the k-th optimization iteration corresponding to the n-th group of tests. is the measured current value at the h-th moment of the k-th optimization iteration corresponding to the n-th group of tests;

[0025] After several rounds of iteration, when the constraint condition formula meets the convergence condition, the final iterative optimization values of resistance and inductance for each group of tests can be obtained, and the final iterative optimization values of resistance and inductance are used as the equivalent resistance and equivalent inductance of the corresponding tests.

[0026] Furthermore, the theoretical calculation formulas for the parallel equivalent resistance, parallel equivalent inductance, parallel active component, and parallel reactive component between different layers of encapsulation are:

[0027] ;

[0028] ;

[0029] ;

[0030] ;

[0031] Among them, Rn, Ln, Pn, and Qn are the theoretical parallel equivalent resistance, parallel equivalent inductance, parallel active component, and parallel reactive component of different encapsulation samples respectively, and n, i, j ∈ [1, N], i, j < n, In represents the effective value of the current passing through the encapsulation sample in the n-th test, and ω is the system electrical angular frequency; combining the physical parameters of the dry-type air-core reactor, the resistance Ri, inductance Li, Lj, and mutual inductance Mij of each layer of encapsulation are obtained according to the finite element method.

[0032] Furthermore, using the equivalent resistance and equivalent inductance corresponding to different layers of encapsulation, the active and reactive components of each group of encapsulations under the test voltage are calculated by combining the discrete values of the test current;

[0033] The relative deviations are calculated between the corresponding theoretical values Rn, Ln, Pn, and Qn and the corresponding equivalent resistance, equivalent inductance, and active and reactive components respectively. If all are lower than the threshold, the uniformity meets the requirements; the calculation formula for the relative deviation is:

[0034] ;

[0035] Among them, Let $R_n$, $L_n$, $P_n$, and $Q_n$ be the theoretical values obtained in the $n$-th time, and the relative deviations between them and the corresponding equivalent resistance, equivalent inductance, and active and reactive components. When the indices , , and are less than the corresponding thresholds, it indicates that the uniformity of the reactor meets the requirements.

[0036] The present invention also provides a dynamic stability current-sharing test system for a large-capacity dry-type air-core reactor, including a test sample group construction module, a test equipment connection module, a data acquisition module, an equivalent parameter calculation module, and a uniformity verification module:

[0037] The test sample group construction module constructs a scaled-down test sample group for the multi-layer large-capacity dry-type air-core reactor test;

[0038] The test equipment connection module, when the switch is closed, connects the encapsulated test sample to the AC synchronous generator through an isolation transformer, connects the current transformer in series with the encapsulated test sample, and installs the voltage divider at both ends of the encapsulated test sample;

[0039] The data acquisition module conducts $N$ tests on the encapsulated test sample and collects a total of $N$ groups of test data, including the test current value;

[0040] The equivalent parameter calculation module, based on the discrete values of the test current, obtains the equivalent resistance and equivalent inductance of the encapsulated sample in the corresponding test; optimizes the equivalent resistance and equivalent inductance in each group of tests to minimize the difference between the corresponding discrete values of the test current and the theoretical current; calculates the active and reactive components based on the equivalent resistance and equivalent inductance of each group of tests after the optimization, combined with the discrete values of the test current;

[0041] The uniformity verification module calculates the parallel equivalent resistance, parallel equivalent inductance, parallel active component, and parallel reactive component of the encapsulated samples in each group, calculates the relative deviation with the corresponding measured values, and if it is lower than the threshold, the uniformity meets the requirements. Description of the Drawings

[0042] Figure 1 is the method flow chart of a dynamic stability current-sharing test method for a large-capacity dry-type air-core reactor of the present invention;

[0043] Figure 2 is the scaled-down test sample schematic diagram of a dynamic stability current-sharing test method for a large-capacity dry-type air-core reactor of the present invention;

[0044] Figure 3 is the equipment connection diagram of a dynamic stability current-sharing test method for a large-capacity dry-type air-core reactor of the present invention.

[0045] Figure 4It is the power supply waveform diagram of a dynamic stability current sharing test method for a large-capacity dry-type air-core reactor of the present invention. Specific embodiments

[0046] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only a part of the embodiments of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0047] Embodiment 1

[0048] The present invention provides a dynamic stability current sharing test method and system for a large-capacity dry-type air-core reactor. The method flow chart is as Figure 1 shown. The specific method steps are as follows:

[0049] Construct a multi-layer encapsulated reduced-scale specimen group for the test of a large-capacity dry-type air-core reactor, as Figure 2 shown, with a total of N specimens, including 1-layer encapsulation, 2-layer encapsulation,..., N-layer encapsulation respectively. Except for the number of encapsulation layers, the rest of the structures are the same. The encapsulated reduced-scale specimen group refers to the equal-proportion reduction of the 500 kV large-capacity dry-type air-core reactor to be tested, keeping the winding connection method and wire material unchanged, and reducing the wire diameter, encapsulation thickness, number of coil turns, coil length, etc. in equal proportion to obtain an encapsulated reduced-scale specimen group with different numbers of encapsulation layers.

[0050] Further, connect the dynamic and thermal stability test equipment to the specimen; connect the AC synchronous generator to the input end of the isolation transformer through a switch, and connect the output end of the isolation transformer to both ends of the specimen encapsulated winding. As Figure 3 shown, it is the equipment connection diagram of the present invention. Among them, when the switch S is closed, the encapsulated specimen L is connected to the AC synchronous generator G through the isolation transformer T. After short-circuit current (about 500 ms) is passed, the switch is disconnected. Among them, the current transformer is connected in series with the encapsulated specimen, and the voltage divider is installed at both ends of the encapsulated specimen. The connection structure of the current transformer, voltage divider and encapsulated specimen is called the test end in this embodiment. The voltage waveform applied to the encapsulated specimen is a power frequency sine component, as Figure 4 shown. Further, connect the 1st to Nth layer encapsulated reduced-scale specimens to the output end of the isolation transformer in turn, apply the same voltage for the test, and the wiring method of the specimen is the same each time, that is, connect both ends of the specimen to the test end. During each test, read the test data of the voltage uL and current iL through the voltage divider and current sensor. A total of N groups of test data are collected, as shown in Table 1, t ∈ [0, T], where T is the total duration of collecting the test data.

[0051] Table 1 Test data

[0052]

[0053] Discretize the data of each test. The total number of discretization points is H. Then, the h-th discrete voltage and current data of the n-th test are respectively and .

[0054] Furthermore, set the initial vectors of the resistance and inductance of the encapsulation in the corresponding test, and use the particle swarm optimization algorithm to iteratively optimize the resistance and inductance of each group of encapsulations. Take the minimization of the difference between the discrete test current value and the theoretical current discrete value calculated based on the iteratively optimized values of resistance and inductance as the constraint condition for iteration. After reaching the convergence criterion, obtain the finally iteratively optimized values of resistance and inductance for each group of encapsulations.

[0055] Specifically, according to the coil parameters of each encapsulation test sample group, calculate the initial vector of the corresponding encapsulation resistance and the initial vector of the inductance by the following formula:

[0056] ;

[0057] ;

[0058] where D is the coil diameter, H is the coil height, ρ is the resistivity of the coil, L is the coil length, and S is the cross-sectional area of the coil;

[0059] For each encapsulation test sample group, based on the initial optimization parameters , use the particle swarm optimization method. The optimization equation is:

[0060] ;

[0061] where the superscripts k and k + 1 are the discrete moments of the particle running process during the particle swarm optimization of the n-th group of test data. k is an integer, k = 1, 2, 3... K, and are the velocities of the particle at the k-th and k + 1-th moments of the particle running process respectively. w is the inertia weight, is the individual optimal position of the particle at the k-th moment of the particle running process, is the global optimal position of the particle at the k-th moment of the particle running process. c1 and c2 are the individual learning factor and the global learning factor respectively. r1 and r2 are the individual random number and the global random number respectively, and are the positions of the particle at the k-th and k + 1-th moments of the particle running process respectively;

[0062] The optimized parameters can be obtained after the k-th round of optimization , by using the optimized parameters, combining with the equivalent RLC circuit of the test platform and the actual voltage excitation waveform, and through discretization processing, the corresponding discrete theoretical current values can be obtained. .

[0063] Furthermore, the particle swarm optimization algorithm is used to obtain the equivalent resistance and equivalent inductance for each corresponding test under each optimization iteration. The theoretical current discrete values corresponding to the iterative optimization values of the resistance and inductance obtained each time are calculated using the test voltage.

[0064] The corresponding encapsulation test currents collected during the test process of the encapsulation shrinkage ratio sample group are discretized to obtain the discrete test current values.

[0065] Furthermore, combining the discrete theoretical current values , the constraint condition formula at the discrete time k during the particle running process is:

[0066] ;

[0067] Among them, and are the equivalent resistance and equivalent inductance of the k-th optimization iteration corresponding to the n-th group of tests respectively, and h = 1,..., H, where H is the number of current test data sampling points. is the measured current value at the h-th moment of the k-th iteration of the n-th group of tests, is the measured current value at the h-th moment of the k-th iteration of the n-th group of tests.

[0068] After several rounds of iteration, when the constraint condition formula meets the convergence condition, the final iterative optimization values of the resistance and inductance for each group of tests can be obtained, and the final iterative optimization values of the resistance and inductance are used as the equivalent resistance and equivalent inductance of the corresponding tests.

[0069] This constraint condition can closely optimize the parameters around the test data. When calculating the equivalent resistance and inductance, it makes the optimization result more in line with the actual measurement situation, ensuring the reliability of the deduced equivalent resistance and inductance parameters. The parameters obtained in this way can more truly reflect the electrical characteristics of the reactor encapsulation, help to accurately evaluate the uniformity between encapsulations, and provide key technical support for ensuring the safe and stable operation of the reactor.

[0070] Furthermore, taking the iterative optimization values of the resistance and inductance of the encapsulation in each group of tests as the equivalent resistance and equivalent inductance of the corresponding encapsulation in each group of tests, the active and reactive components of the encapsulation under the test voltage are calculated in combination with the discrete test current values, as shown in Table 2.

[0071] Table 2 Parameter Examples

[0072]

[0073] Calculate the theoretical parallel equivalent resistance, parallel equivalent inductance, parallel active component and parallel reactive component of the encapsulations in each group, calculate the relative deviation from the corresponding measured values respectively. If all relative deviations are lower than the threshold, the uniformity meets the requirements.

[0074] Specifically, the theoretical calculation formulas for the parallel equivalent resistance, parallel equivalent inductance, parallel active component and parallel reactive component between encapsulations with different numbers of layers are as follows:

[0075] ;

[0076] ;

[0077] ;

[0078] ;

[0079] Among them, Rn, Ln, Pn and Qn are the theoretical parallel equivalent resistance, parallel equivalent inductance, parallel active component and parallel reactive component after parallel connection of each encapsulation respectively, and n, i, j ∈ [1, N], i, j < n, In represents the effective value of the current passing through the encapsulation sample in the nth test, ω is the system electrical angular frequency; combined with the physical parameters of the dry-type air-core reactor, the resistance Ri, inductance Li, Lj and Mij of each layer of encapsulation are obtained according to the finite element method.

[0080] Furthermore, using the equivalent resistance and equivalent inductance corresponding to different numbers of layers of encapsulations, the active and reactive components of each group of encapsulations under the test voltage are calculated in combination with the discrete values of the test current;

[0081] Calculate the relative deviation of the corresponding theoretical values Rn, Ln, Pn and Qn from the corresponding equivalent resistance, equivalent inductance, and active and reactive components respectively. If all are lower than the threshold, the uniformity meets the requirements; the calculation formula for the relative deviation is:

[0082] ;

[0083] Among them, is the relative deviation between the theoretical values Rn, Ln, Pn and Qn obtained in the nth time and the corresponding equivalent resistance, equivalent inductance, and active and reactive components. When the indicators , , and are less than the corresponding thresholds, it indicates that the uniformity of the reactor meets the requirements.

[0084] By calculating the parallel equivalent parameters, the electrical performance differences between different packages can be intuitively compared. If the difference between the theoretical parallel equivalent parameters of the packages and the measured values is small, it indicates good package uniformity; otherwise, there are problems. This helps to promptly detect possible defects in the design or manufacturing process of the reactor, so as to optimize and improve the reactor and enhance its overall performance and operation reliability.

[0085] The present invention also proposes a dynamic stability current-sharing test system for a large-capacity dry-type air-core reactor, including a test sample group construction module, a test equipment connection module, a data acquisition module, an equivalent parameter calculation module, and a uniformity verification module:

[0086] The test sample group construction module constructs a reduced-scale test sample group of packages for testing a multi-layer large-capacity dry-type air-core reactor;

[0087] The test equipment connection module, when the switch is closed, connects the package test sample to the AC synchronous generator through an isolation transformer, the current transformer is connected in series with the package test sample, and the voltage divider is installed at both ends of the package test sample;

[0088] The data acquisition module conducts N tests on the package test sample and collects a total of N groups of test data, including the test current value;

[0089] The equivalent parameter calculation module, based on the discrete values of the test current, obtains the equivalent resistance and equivalent inductance of the package in the corresponding test; optimizes the equivalent resistance and equivalent inductance in each group of tests to minimize the difference between the corresponding discrete value of the test current and the theoretical discrete value of the current; calculates the active and reactive components according to the equivalent resistance and equivalent inductance of each group of tests after the optimization is completed, in combination with the discrete value of the test current;

[0090] The uniformity verification module calculates the parallel equivalent resistance, parallel equivalent inductance, parallel active component, and parallel reactive component of the packages in each group, calculates the relative deviation from the corresponding measured value, and if it is lower than the threshold, the uniformity meets the requirements.

[0091] Embodiment 2

[0092] This embodiment makes a further improvement on the basis of Embodiment 1.

[0093] In this embodiment, when constructing a reduced-scale test sample group of packages for testing a multi-layer large-capacity dry-type air-core reactor, considering cost issues, the number of layers of the reduced-scale test sample group of packages can also be gradually increased to 2, 3, or other integers not greater than N / 2. The more the number of the reduced-scale test sample group of packages, the more obvious the uniformity verification effect. The number of layers of the packages can be but is not limited to this way: such as 1, 3, 5, 9, 12, etc., that is, the number of layers can be not in an arithmetic progression.

[0094] In this embodiment, the specific steps for simulating the equivalent resistance and equivalent inductance of the package in the corresponding test are:

[0095] Taking the equivalent resistance and equivalent inductance corresponding to each group of tests as the optimization objects, an optimization equation is constructed;

[0096] The constraint condition for the optimization equation is to minimize the difference between the measured current value and the estimated current value in the test data.

[0097] Among them, the optimization algorithm can be but not limited to the least squares method, the simulated annealing algorithm, and the genetic algorithm.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific implementation manners of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A dynamic stability current sharing test method for a large-capacity dry-type air-core reactor, characterized in that Including: Construct a set of reduced-scale test specimens for the multi-layer large-capacity dry-type air-core reactor to be tested, with a total of N specimens, including 1-layer, 2-layer,..., N-layer envelopes respectively; connect the dynamic and thermal stability test equipment to the test specimens; Connect the AC synchronous generator to the input end of the isolation transformer through a switch, and connect the output end of the isolation transformer to both ends of the test specimen envelope winding; sequentially connect the reduced-scale test specimens of 1 to N layers to the output end of the isolation transformer, apply the same voltage for testing, and collect test data; Set the initial vectors of the resistance and inductance of the envelopes in the corresponding tests, and use the particle swarm optimization algorithm to iteratively optimize the resistance and inductance of each group of envelopes. Take the minimization of the difference between the discrete value of the test current and the theoretical current discrete value calculated based on the iteratively optimized values of the resistance and inductance as the constraint condition for iteration. After reaching the convergence criterion, obtain the finally iteratively optimized values of the resistance and inductance of each group of envelopes; Use the iteratively optimized values of the resistance and inductance of the envelopes in each group of tests as the equivalent resistance and equivalent inductance of the corresponding envelopes in each group of tests, and calculate the active and reactive components of the envelopes in each group of tests under the test voltage in combination with the discrete value of the test current; calculate the theoretical parallel equivalent resistance, parallel equivalent inductance, parallel active component and parallel reactive component of the envelopes in each group, and calculate the relative deviation with the corresponding measured values respectively. If all relative deviations are lower than the threshold, the uniformity meets the requirements.

2. A dynamic stability current sharing test method for a large-capacity dry-type air-core reactor according to claim 1, characterized in that: The set of reduced-scale test specimens of envelopes refers to the equal-proportion reduction of the large-capacity dry-type air-core reactor to be tested, keeping the winding connection method and wire material unchanged, and reducing the wire diameter, envelope thickness, coil turns, coil length, etc. in equal proportion to obtain a set of reduced-scale test specimens of envelopes with different envelope layers.

3. A dynamic stability current sharing test method for a large-capacity dry-type air-core reactor according to claim 1, characterized in that: During each test, the applied test voltage is the same, and the test voltage value is determined according to the wire diameter and envelope layer thickness of the reduced-scale test specimen group.

4. A dynamic stability current sharing test method for a large-capacity dry-type air-core reactor according to claim 3, characterized in that: During each test, measure the test voltage value applied to the set of reduced-scale test specimens of envelopes through a voltage divider, and measure the test current value of the set of reduced-scale test specimens of envelopes through a current transformer.

5. A dynamic stability current sharing test method for a large-capacity dry-type air-core reactor according to claim 1, characterized in that: According to the coil parameters of each package of test samples, calculate the corresponding initialization vector of the package resistance and the initialization vector of the inductance as follows: ； ； Wherein, D is the coil diameter, H is the coil height, ρ is the resistivity of the coil, L is the coil length, and S is the coil cross-sectional area.

6. A dynamic stability current-sharing test method for a large-capacity dry-type air-core reactor according to claim 5, characterized in that: For each packet of encapsulation ratio test samples, based on the initial optimization parameters , the particle swarm optimization method is used, and the optimization equation is: ； Among them, the superscripts k and k + 1 are the discrete moments of the particle running process during the particle swarm optimization process for the nth group of test data. k is an integer, and k = 1, 2, 3... K. and are the velocities of the particle at the kth and (k + 1)th moments of the particle running process respectively. w is the inertia weight. is the individual optimal position of the particle at the kth moment of the particle running process. is the global optimal position of the particle at the kth moment of the particle running process. c1 and c2 are the individual learning factor and the global learning factor respectively. r1 and r2 are the individual random number and the global random number respectively. and are the positions of the particle at the kth and (k + 1)th moments of the particle running process respectively.

7. A dynamic stability current sharing test method for a large-capacity dry-type air-core reactor according to claim 6, characterized in that: Use the particle swarm optimization algorithm to obtain the equivalent resistance and equivalent inductance in each optimization iteration of the corresponding test, and use the test voltage to calculate the theoretical current discrete value corresponding to the iteratively optimized values of the resistance and inductance obtained each time; The corresponding envelope test current collected during the test of the envelope shrinkage ratio sample group is discretized to obtain the discrete value of the test current.

8. A dynamic stability current sharing test method for a large-capacity dry-type air-core reactor according to claim 7, characterized in that: Combined with the discrete values of the theoretical current , the constraint condition formula at the discrete time k during the particle operation process is as follows: ； Among them, and are the equivalent resistance and equivalent inductance after the k-th optimization iteration corresponding to the n-th group of tests, respectively, and h = 1,..., H, where H is the number of current test data sampling points. is the measured current value at the h-th moment after the k-th optimization iteration corresponding to the n-th group of tests. is the measured current value at the h-th moment after the k-th optimization iteration corresponding to the n-th group of tests. After several rounds of iteration, when the constraint condition formula meets the convergence condition, the final iterative optimization values of the resistance and inductance of each group of tests can be obtained, and the final iterative optimization values of the resistance and inductance are used as the equivalent resistance and equivalent inductance of the corresponding test.

9. A dynamic stability current sharing test method for a large-capacity dry-type air-core reactor according to claim 1, characterized in that: The theoretical calculation formulas for the parallel equivalent resistance, parallel equivalent inductance, parallel active component and parallel reactive component between different layers of envelopes are: ； ； ； ； Among them, Rn, Ln, Pn and Qn are the theoretical parallel equivalent resistance, parallel equivalent inductance, parallel active component and parallel reactive component of different envelope samples respectively, and n, i, j ∈ [1, N], i, j < n, In represents the effective value of the current passing through the envelope sample in the nth test, and ω is the system electrical angular frequency; combined with the physical parameters of the dry-type air-core reactor, the resistance Ri, inductance Li, Lj and Mij of each layer of envelope are obtained according to the finite element method.

10. A dynamic stability current sharing test method for a large-capacity dry-type air-core reactor according to claim 9, characterized in that: Using the equivalent resistance and equivalent inductance corresponding to different layers of envelopes, the active and reactive components of each group of envelopes under the test voltage are calculated in combination with the discrete value of the test current; The relative deviations of the corresponding theoretical values Rn, Ln, Pn and Qn from the corresponding equivalent resistance, equivalent inductance, and active and reactive components are calculated respectively. If they are all lower than the threshold value, the uniformity meets the requirements; the calculation formula for the relative deviation is: ； wherein, is the relative deviation between the theoretical values Rn, Ln, Pn, and Qn obtained in the nth time and the corresponding equivalent resistance, equivalent inductance, and active and reactive components. When the indexes , , and are less than the corresponding thresholds, it indicates that the uniformity of the reactor meets the requirements.

11. A dynamic stability current sharing test system for a large-capacity dry-type air-core reactor based on the method according to any one of claims 1-10, including a sample group construction module, a test equipment connection module, a data acquisition module, an equivalent parameter calculation module and a uniformity verification module, characterized in that: The sample group construction module constructs a multi-layer envelope shrinkage ratio sample group for the test of a large-capacity dry-type air-core reactor; The test equipment connection module, when the switch is closed, the envelope sample is connected to the AC synchronous generator through an isolation transformer, the current transformer is connected in series with the envelope sample, and the voltage divider is installed at both ends of the envelope sample; The data acquisition module conducts N tests on the envelope sample and collects a total of N groups of test data, including the test current value; The equivalent parameter calculation module, based on the discrete value of the test current, obtains the equivalent resistance and equivalent inductance of the envelope in the corresponding test; optimizes the equivalent resistance and equivalent inductance in each group of tests to minimize the difference between the corresponding discrete value of the test current and the theoretical discrete value of the current; according to the equivalent resistance and equivalent inductance of each group of tests after the optimization is completed, the active and reactive components are calculated in combination with the discrete value of the test current; The uniformity verification module calculates the parallel equivalent resistance, parallel equivalent inductance, parallel active component, and parallel reactive component of the encapsulation in each group, calculates the relative deviation from the corresponding measured value, and if it is lower than the threshold, the uniformity meets the requirements.

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