Simplified modeling and simulation method for complex roof grid structure of bridge arm reactor room

Abstract

The application relates to the field of finite element simulation modeling in electrical equipment reliability verification, and discloses a simplified modeling simulation method of a complex roof net rack structure of a bridge arm reactor room, which comprises the following steps: establishing a pyramid net rack unit model in finite element software; performing array operation to obtain a local net rack model, which is placed above a single bridge arm reactor, excitation current is applied to the bridge arm reactor, local steel structure heating simulation law research is carried out in the finite element software, and the pyramid net rack unit model is simplified; and the pyramid net rack unit model capable of reflecting maximum temperature rise is selected to perform array or rotation operation, and a whole model is established. The simplified modeling simulation method of the complex roof net rack structure of the bridge arm reactor room researches the local heating law of the net rack structure and simplifies the whole model, reduces the number of whole net rack model grids to an acceptable range, and provides reference value for actual engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of finite element simulation modeling in electrical equipment reliability verification, and particularly relates to a simplified modeling simulation method for a complex roof grid structure of a bridge arm reactor room. BACKGROUND

[0002] As a new generation of DC transmission technology, flexible DC transmission is different from the current source converter high voltage DC transmission based on phase control commutation technology. The converter in the flexible DC transmission is a voltage source converter (VSC), and the biggest feature is that it uses a blocking device (usually IGBT) and high frequency modulation technology. By adjusting the amplitude of the converter outlet voltage and the power angle difference with the system voltage, the active power and reactive power output can be independently controlled. In this way, through the control of the two end converter stations, the active power between the two AC networks can be transmitted, and the two end converter stations can also independently adjust the reactive power absorbed or emitted, thereby providing reactive power support to the connected AC system. Flexible DC transmission is an important equipment for building smart grid, and compared with the traditional way, it has strong technical advantages in island power supply, capacity expansion and reconstruction of urban distribution network, AC system interconnection, large-scale wind farm grid connection, etc. It is a strategic choice to change the development pattern of large power grid.

[0003] The bridge arm reactor is located at the DC side or AC side of the flexible DC transmission converter valve, and the leakage reactance between it and the coupling transformer together constitutes the circulating current reactor of the converter station, mainly playing the role of controlling power transmission, filtering and suppressing AC side current fluctuations, and also suppressing the circulating current between the bridge arms and the rapidly rising bridge arm fault current during short circuit. The valve hall and bridge arm reactor room of the full indoor and fully enclosed arrangement have compact structure, and the metal structure meets the magnetic safety distance of the reactor at the beginning of design. However, the metal structure may still heat up during the operation of the bridge arm reactor, causing certain safety problems. In order to predict and analyze the parts of the indoor bridge arm reactor around the steel structure that are prone to heating and the temperature rise value, the complete structure needs to be modeled and simulated to determine the heating points with high current density in the metal structure under the influence of circulating current. However, the actual steel structure, such as the roof grid of the converter station, has complex structure and is difficult to model, and after modeling, the finite element grid division may be too dense and consume too much computing resources, making it impossible to calculate. SUMMARY

[0004] The purpose of the present application is to overcome the above technical deficiencies, and to provide a simplified modeling simulation method for a complex roof grid structure of a bridge arm reactor room. The local heating law of the grid structure is studied and the overall model is simplified, the number of grid points of the overall grid model is reduced to an acceptable range, and the feasibility of large-scale electromagnetic heat calculation in the simulation research of the heating problem of the steel structure around the bridge arm reactor is confirmed, providing reference value for actual engineering.

[0005] In order to achieve the above-mentioned purpose, the bridge arm reactor chamber complex roof grid structure simplification modeling simulation method relates to the following steps:

[0006] According to the roof grid structure drawing, a pyramid grid unit model is established in the finite element software, including parameterized grid bars and welding balls;

[0007] The pyramid grid unit model is subjected to array operation to obtain an X*X size local grid model, X is not less than 2, the local grid model is placed above a single bridge arm reactor, an exciting current is applied to the bridge arm reactor, local steel structure heating simulation law research is carried out in the finite element software, the influence of the thickness and hollow of the grid bars and the size of the welding balls on the maximum temperature rise of the local grid model surface is explored, and the pyramid grid unit model is simplified according to the obtained results.

[0008] Since the pyramid grid unit models involved in the actual grid structure have different sizes, the pyramid grid unit model reflecting the maximum temperature rise is selected according to the structure drawing to carry out array or rotation operation, and the overall model of the roof grid structure above the bridge arm reactor chamber is established.

[0009] Preferably, the grid bars include transverse bars and longitudinal bars, the control parameters of the pyramid grid unit model include the inner diameter and outer diameter of the grid bars, the inner diameter and outer diameter of the welding balls, and the length of the transverse bars and longitudinal bars.

[0010] Preferably, the pyramid grid unit model is a parameterized three-dimensional model.

[0011] Preferably, the local grid model is a region that can reflect the temperature rise of the roof grid caused by the circulating current and has a size greater than the diameter of the bridge arm reactor.

[0012] Preferably, the overall model is all corresponding roof grid regions above the bridge arm reactor chamber.

[0013] Preferably, the overall model is subjected to mesh division in the finite element software, the number of meshes is adjusted, and the tetrahedral vertex number of the mesh is not more than 300,000, so as to ensure the calculation speed.

[0014] Compared with the prior art, the present application has the following advantages: the local heating law of the grid structure is researched and the overall model is simplified, the number of overall grid models is reduced to an acceptable range, the feasibility of large-scale electromagnetic heat calculation in the simulation research of the heating problem of the steel structure around the bridge arm reactor is verified, and reference value is provided for actual engineering. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1The structural diagram of the pyramid net rack unit model in step A) of the simplified modeling simulation method of the complex roof net rack structure of the bridge arm reactor room of the application;

[0016] Figure 2 The schematic diagram of the establishment of the local net rack model in step B) of the simplified modeling simulation method of the complex roof net rack structure of the bridge arm reactor room of the application;

[0017] Figure 3 The schematic diagram of the size of the finally selected pyramid net rack unit model after simplification in step B) of the simplified modeling simulation method of the complex roof net rack structure of the bridge arm reactor room of the application;

[0018] Figure 4 The structural diagram of the overall model in step C) of the simplified modeling simulation method of the complex roof net rack structure of the bridge arm reactor room of the application;

[0019] Figure 5 The simulation structure of one embodiment of the simplified modeling simulation method of the complex roof net rack structure of the bridge arm reactor room of the application.

[0020] The labels of the components in the figure are as follows:

[0021] The net rack rod 1, the welded ball 2, the local net rack model 3, and the bridge arm reactor 4. DETAILED DESCRIPTION

[0022] The application will be further described in detail below in combination with specific embodiments and the accompanying drawings.

[0023] A simplified modeling simulation method of a complex roof net rack structure of a bridge arm reactor room, comprising the following steps:

[0024] A) According to the structural drawing of the roof net rack, a pyramid net rack unit model is established in the finite element software, the pyramid net rack unit model is a parameterized three-dimensional model, including parameterized net rack rods 1 and welded balls 2, the net rack rods 1 include transverse rods and longitudinal rods, since the net rack rods 1 of different positions in the drawing are of different types and the sizes of the welded balls 2 are not uniform, the control parameters of the pyramid net rack unit model include the inner diameter and the outer diameter of the net rack rods 1, the inner diameter and the outer diameter of the welded balls 2, and the length of the transverse rods and the longitudinal rods, as shown in the drawing, a three-dimensional model is established using Comsol Multiphysics, each unit includes 8 net rack rods 1 and 2 welded balls 2; Figure 1

[0025] ​B) Array operation is performed on the pyramid grid unit model to obtain a 3*3 size local grid model 3, the local grid model 3 is a region capable of reflecting the temperature rise of the roof grid caused by the circulation and larger than the diameter of the bridge arm reactor 4, the local grid model 3 is placed above the single bridge arm reactor 4, the excitation current is applied to the bridge arm reactor 4, the heating simulation law of the local steel structure is studied in the finite element software, the influence of the thickness and hollow of the grid bar and the size of the welding ball on the maximum temperature rise of the surface of the local grid model 3 is explored, the pyramid grid unit model is simplified according to the obtained results, and the local grid model 3 shown in Figure 1 is obtained by performing 3*3 array operation on the pyramid grid unit model in Figure 2 , which is used to study the influence law of various parameters on the heating of the grid in step 1, and the heating conditions of the above-mentioned different size hollow bars are studied, the maximum temperature rise under each size is shown in Table 1:

[0026] Table 1 Simulation results of local models of different types of steel pipes

[0027]

[0028] From the results, it can be seen that the heating caused by different sizes of grid bars 1 has certain differences, so it is not appropriate to replace all grids with the same size grid bars 1, but as the radius of the grid bar 1 increases, the surface area of the grid bar 1 gradually increases, that is, its heat dissipation capacity increases, and as the wall thickness of the grid bar 1 increases, its resistance decreases, and the heating decreases, so the thicker the steel pipe, the less likely it is to heat, according to the results of multiple attempts, the modeling of the overall grid is limited by rendering capacity, mesh division and computing resources, it is difficult to simulate hollow steel pipes, if it is changed to solid steel pipes, it can greatly save computing resources, the heating results of the hollow model and the solid model of the 88*4 type grid bar 1 are compared as shown in Table 2:

[0029] Table 2 Comparison of temperature rise of solid and hollow steel pipe models

[0030]

[0031] Since the sizes of the welding balls 2 actually taken are different, and modeling according to different sizes is too complex, it is hoped that the size of the welding ball 2 in the simulation model can be unified, the influence of different sizes of welding balls 2 on the maximum temperature rise, for the solid welding ball model established when the size of the grid bar 1 is 88*4, the radius is changed, the surface maximum temperature rise of the local grid model 3 under different sizes of welding balls 2 is obtained, as shown in Table 3:

[0032] Table 3 Comparison of temperature rise of different radius hollow welding ball models

[0033]

[0034] The simulation analysis shows that the temperature rise difference between the hollow and solid steel pipes of the truss member 1 is not large, about 10%, in order to reduce the demand of modeling on computer rendering capability, mesh division and computing resources, the truss member 1 can be modeled as solid, and the final simulation result is enlarged by 10% as the actual simulation result of the hollow pipe, the selection of the radius of the welding ball 2 has little effect on the simulation result, so in the actual modeling process, the radius of the welding ball 2 can be uniformly considered as 246.4 mm, the truss member 1 of different positions in the drawing adopts different types, and the truss member 1 of each basic pyramid truss unit model is replaced by the smallest truss member 1 at the same position;

[0035] C) Since the pyramid truss unit models involved in the actual truss structure have different sizes, the pyramid truss unit model reflecting the maximum temperature rise is selected according to the structural drawing for array or rotation operation to establish the overall model of the roof truss structure above the bridge reactor room, and the overall model is all the corresponding roof truss regions above the bridge reactor room, in this embodiment, according to the structural drawing, the minimum member size of the lower chord in the north-south direction is Φ140×4, the minimum member size of the lower chord in the east-west direction is Φ88.4×4, the minimum member size of the upper chord in the north-south direction is Φ88.4×4, the minimum member size of the upper chord in the east-west direction is Φ114×4, and the minimum size of the web member is Φ114×4, according to the previous conclusion, the finer the size of the truss member 1, the more likely the heating phenomenon occurs, therefore, the longitudinal, transverse and diagonal bracing steel pipes are respectively replaced by the smallest solid steel pipes to simulate more severe conditions, since the truss members 1 far from the bridge reactor 4 will not have a heating phenomenon, therefore, the part of the truss of the entire building roof truss 11 shaft~14 shaft is selected for modeling (the longitudinal direction covers all the trusses of the A shaft~G shaft), the truss inclination angle is consistent with the actual one, the truss lower end elevation is 21.7 m, the truss transverse direction includes 4.5 quadrilateral conical grids, and the truss longitudinal direction includes 21 quadrilateral conical grids, and the overall view of the truss is shown in Figure 4 .

[0036] In addition, in order to facilitate calculation, the overall model is meshed in the finite element software, the number of meshes is adjusted, the calculation resources are optimized, the temperature rise calculation of the roof net rack structure under the influence of the indoor bridge reactor 4 magnetic field is carried out, and reliable reference is provided for preventing and treating the heating phenomenon of the steel structure around the DC room bridge reactor 4. In the embodiment, the complete simulation calculation model should include the six bridge reactors 4 in the indoor bridge reactor room, the complete net rack structure above the reactor and the simulation domain including the above two entities. The bottom height of the bridge reactor 4 is 2.97m, the self height is 9.276m, the inner diameter is 2.08m, the outer diameter is 3.05m, the number of turns is 213 turns, the phase sequence of the six bridge reactors 4 is AABBCC, the effective value of the fundamental frequency current flowing through 854A is set under the working condition, the DC component and the two times frequency component are ignored, the net rack material is Q235b steel, the metal surface convective heat transfer coefficient is selected as 8.7 according to the lower standard of natural convection in indoor heating design, the environmental temperature is set as 293.15K, the simulation model is meshed, the "refinement" mesh density division option is used for the net rack, and the "normal" mesh density division option is used for other areas. The final calculated tetrahedral vertex number is not more than 300,000, so as to ensure the calculation speed. The simulation result is shown in Figure 5 The highest temperature rise of the net rack is 5.3K, which appears in the boxed part directly above the A-phase bridge reactor 4, and the heating does not exceed the temperature rise limit value of 50K, so no heating suppression measures are needed.

[0037] The simplified modeling simulation method of the complex roof net rack structure of the bridge reactor room of the application studies the local heating law of the net rack structure and simplifies the overall model. The number of meshes of the overall net rack model is reduced to an acceptable range, which proves the feasibility of large-scale electromagnetic heat calculation in the simulation research of the heating problem of the steel structure around the bridge reactor 4, and provides reference value for actual engineering.

Claims

1. A method for simplifying modeling simulation of a bridge-arm reactor room complex roof grid structure, characterized in that: It comprises the following steps: According to the structural drawing of the roof grid, a pyramid grid unit model is established in the finite element software, including parameterized grid bars (1) and welded balls (2); The pyramid grid unit model is subjected to array operation to obtain an X*X size local grid model (3), X is not less than 2, the local grid model (3) is placed above a single bridge arm reactor (4), the bridge arm reactor (4) is applied with exciting current, and local steel structure heating simulation law research is carried out in the finite element software, the influence of the thickness and hollow of the grid bars (1) and the size of the welded balls (2) on the maximum temperature rise of the local grid model (3) is explored, and the pyramid grid unit model is simplified according to the obtained results; The pyramid grid unit model reflecting the maximum temperature rise is selected according to the structural drawing and subjected to array or rotation operation to establish a whole model of the roof grid structure above the bridge arm reactor room.

2. The method of claim 1, wherein the method is characterized by: The grid bars (1) include transverse bars and longitudinal bars, the control parameters of the pyramid grid unit model include the inner diameter and outer diameter of the grid bars (1), the inner diameter and outer diameter of the welded balls (2), and the length of the transverse bars and longitudinal bars.

3. The method of claim 1, wherein the method is characterized by: The pyramid grid unit model is a parameterized three-dimensional model.

4. The method of claim 1, wherein the method is characterized by: The local grid model (3) is a region that can reflect the temperature rise of the roof grid caused by circulating current and has a size larger than the diameter of the bridge arm reactor (4).

5. The method of claim 1, wherein the method further comprises: The whole model is all corresponding roof grid regions above the bridge arm reactor room.

6. The method of claim 1, wherein the method further comprises: The whole model is subjected to mesh division in the finite element software, and the number of meshes is adjusted, and the tetrahedral vertex number of the mesh is not more than 300,000.

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