Rapid calculation method for transient thermal field of direct-current wall bushing and related device

Abstract

The invention belongs to the technical field of power equipment insulation structure design, and discloses a transient thermal field rapid calculation method of a direct current wall bushing and a related device. An energy conservation equation is discretized in time and space, and a finite element equation based on a pre-established finite element simulation model is established; simplifying the finite element equation to obtain a rapid calculation equation; during simplification, the earliest moment influencing transient thermal field distribution of the direct current wall bushing at any moment is determined, and influence items of thermal field distribution at the moment before the earliest moment in the finite element equation on the transient thermal field of the direct current wall bushing at any moment are deleted; determining a heating coefficient in the rapid calculation equation at any moment to obtain a rapid calculation model corresponding to the rapid calculation equation; and calculating the transient thermal field distribution of the direct-current wall bushing at any moment according to the rapid calculation model. According to the method, rapid calculation of transient thermal field distribution of the direct-current wall bushing can be met.

Description

Technical Field

[0001] The present invention belongs to the technical field of insulation structure design of power equipment, and particularly relates to a method for rapidly calculating the transient thermal field of a DC wall bushing and related devices. Background Art

[0002] A converter station is the central link for energy conversion in an AC-DC power transmission system and is also a key node in the backbone grid. With the increase in the voltage level and transmission capacity of DC transmission projects, the technical requirements for converter station equipment have been significantly improved, and the operation and maintenance difficulty of the equipment has increased substantially. As a key device in the converter station, the safe and stable operation of the DC wall bushing is of great significance to the DC project and the power grid system. During operation, the equipment is under the combined action of complex electric, thermal, and mechanical multi-physical fields for a long time, with a complex and changeable internal state and a high failure risk rate. If the defect faults of the DC wall bushing in the converter station are not discovered and disposed of in time, it will cause significant power and economic losses and even endanger the safety of the power grid. Therefore, it is urgent to improve the state analysis and fault diagnosis capabilities of the DC wall bushing in the converter station, enhance the equipment health management and operation and maintenance decision-making levels, and ensure the reliable and stable operation of the equipment.

[0003] Physical field simulation analysis technology is a numerical calculation method that uses the finite element method to solve field problems described by differential equations. With the progress of simulation theory and computer technology, it has now become a very mature technology, and many commercial software has the function of finite element simulation calculation of the thermal field.

[0004] However, for the multi-physical field simulation technology based on traditional finite elements, when the target equipment reaches a certain size, the number of grid calculation nodes increases on a large scale. Especially for models that span multiple scales geometrically, it will cause a large amount of calculation and severely restrict the calculation efficiency. The slow iterative convergence speed of the multi-physical field simulation has become a bottleneck restricting the internal characteristic visualization and real-time evaluation analysis of the panoramic perception information fusion of power equipment. Therefore, in order to achieve real-time simulation and visualization state evaluation of power equipment such as DC wall bushings, it is urgent to develop model reduction methods, master the rapid calculation technology of the bushing thermal field, greatly reduce the time required for simulation calculation, and improve the efficiency of simulation calculation. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a method for rapidly calculating the transient thermal field of a DC wall bushing and related devices. The present invention can meet the rapid calculation of the transient thermal field distribution of the DC wall bushing, improve the operation efficiency, and ensure the accuracy of the calculation results.

[0006] To achieve the above object, the present invention is realized by adopting the following technical solutions: A method for rapidly calculating the transient thermal field of a DC wall bushing, comprising: Discretize the energy conservation equation in time and space, and establish a finite element equation based on the pre-established finite element simulation model of the transient thermal field of a DC wall bushing; Simplify the finite element equation to obtain a fast calculation equation for the finite element simulation model of the transient thermal field of the DC wall bushing; when simplifying the finite element equation, determine the earliest time that affects the transient thermal field distribution of the DC wall bushing at any time, and delete the influence term of the thermal field distribution at the previous time of the earliest time on the transient thermal field of the DC wall bushing at any time in the finite element equation; Determine the heat generation coefficient in the fast calculation equation at the arbitrary time to obtain the fast calculation model corresponding to the fast calculation equation at the arbitrary time; According to the fast calculation model, calculate the transient thermal field distribution of the DC wall bushing at the arbitrary time.

[0007] Preferably: The material in the finite element simulation model of the transient thermal field of the DC wall bushing is set as an isotropic material, and the material parameters include the thermal conductivity parameters of the material, and the thermal conductivity parameters include the thermal conductivity, constant pressure heat capacity and density of the material; In the finite element simulation model of the transient thermal field of the DC wall bushing, the boundary condition of the DC wall bushing is the convective heat transfer coefficient between the surface of the DC wall bushing structure exposed to the fluid and the fluid.

[0008] Preferably: The finite element equation is as follows:

[0009] Wherein, is the thermal field distribution vector at time n , is the thermal field distribution vector at time k , time k is a certain time before time n , and are both stiffness matrices, M is the set of all heat sources, is the heat generation coefficient of the heat source i in the set M at time m , is the heat source m ,

[0010] Preferably, the heat source is the heating rod of the DC wall bushing, or the fluid that conducts convective heat transfer with the DC wall bushing.

[0011] Preferably: When the heat source is the heating rod of the DC wall bushing, the heat generation coefficient is the heating power of the heating rod of the DC wall bushing; When the heat source is a fluid that conducts convective heat transfer with the DC wall bushing, the heating coefficient is the temperature of the fluid.

[0012] Preferably, the fast calculation equation is as follows:

[0013]

[0014] Wherein, k and n represent different moments. The moment k is a certain moment before the moment n . is the thermal field distribution vector at the moment n . M is the set of all heat sources. is the heating coefficient of the heat source i in the set M at the moment m . and are both stiffness matrices. is the heat source field generated by the unit heat of the heat source m .

[0015] Preferably, for a certain moment after the arbitrary moment, calculating the transient thermal field distribution of the DC wall bushing at the certain moment includes: Determining the heating coefficient in the fast calculation equation at the certain moment to obtain the fast calculation equation at the certain moment; Calculating the transient thermal field distribution of the DC wall bushing at the certain moment according to the fast calculation equation at the certain moment; Wherein, the time interval between the certain moment and the arbitrary moment is equal to the time interval between the arbitrary moment and the earliest moment.

[0016] The present invention also provides a fast calculation system for the transient thermal field of a DC wall bushing, which is used to implement the fast calculation method for the transient thermal field of the DC wall bushing of the present invention, including: Finite element equation establishment module: used to discretize the energy conservation equation in time and space and establish a finite element equation based on the pre-established transient thermal field finite element simulation model of the DC wall bushing; Finite element equation simplification module: used to simplify the finite element equation to obtain the fast calculation equation of the transient thermal field finite element simulation model of the DC wall bushing; when simplifying the finite element equation, determining the earliest moment that affects the transient thermal field distribution of the DC wall bushing at any moment, and deleting the influence term of the thermal field distribution at the moment before the earliest moment on the transient thermal field of the DC wall bushing at any moment; The first calculation module: used to determine the heat generation coefficient in the fast calculation equation at any given moment, and obtain the fast calculation model corresponding to the fast calculation equation at any given moment; The second calculation module: used to calculate the transient thermal field distribution of the DC wall bushing at any given moment according to the fast calculation equation at any given moment.

[0017] The present invention also provides an electronic device, including: One or more processors; A storage device, on which one or more programs are stored; When the one or more programs are executed by the one or more processors, the one or more processors are caused to implement the method for rapidly calculating the transient thermal field of the DC wall bushing as described above in the present invention.

[0018] The present invention also provides a storage medium, on which a computer program is stored, wherein when the computer program is executed by a processor, the method for rapidly calculating the transient thermal field of the DC wall bushing as described above in the present invention is implemented.

[0019] The present invention has the following beneficial effects: The method for rapidly calculating the transient thermal field of the DC wall bushing in the present invention comprehensively considers the calculation rate and accuracy when calculating the transient thermal field. By storing the contribution of the heat source to the transient thermal field distribution within a certain time length, and ignoring the contribution of the heat source and the initial temperature distribution outside this time length to the transient thermal field distribution (that is, determining the earliest moment that affects the transient thermal field distribution of the DC wall bushing at any given moment, and deleting the influence term of the thermal field distribution at the moment before the earliest moment in the finite element equation on the transient thermal field of the DC wall bushing at any given moment), the operation time for calculating the transient thermal field distribution is greatly reduced, and at the same time, the influence on the calculation accuracy is ensured to be within a certain control range. Therefore, the present invention can meet the rapid calculation of the transient thermal field distribution of the DC wall bushing, improve the operation efficiency, and ensure the accuracy of the calculation results. Description of the Drawings

[0020] Figure 1 It is a flowchart of the method for rapidly calculating the transient thermal field of the DC wall bushing in the present invention; Figure 2(a) is a thermal field temperature nephogram of the 400kV DC wall bushing in the fast calculation of Embodiment 1 of the present invention; Figure 2(b) is a thermal field temperature nephogram of the 400kV DC wall bushing in the iterative calculation of Embodiment 1 of the present invention; Figure 3 It is a graph of the highest temperature at different moments in the fast calculation and iterative calculation of the 400kV DC wall bushing in Embodiment 1 of the present invention. Detailed Embodiments

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0022] See Figure 1 , the fast calculation method for the transient thermal field of the DC wall bushing of the present invention includes the following steps: Step 1) Establish a finite element simulation model for the transient thermal field of the DC wall bushing: The establishment process of the finite element simulation model for the transient thermal field of the DC wall bushing includes: according to the geometric parameters of the wall bushing, establish a geometric model of the DC wall bushing, perform mesh division on the geometric model of the DC wall bushing, set the materials, material parameters used for each structure of the DC wall bushing, and the boundary conditions of the DC wall bushing to obtain the finite element simulation model for the transient thermal field of the DC wall bushing; when performing mesh division on the geometric model of the DC wall bushing, it should be based on the geometric model of the DC wall bushing and the materials used for each structure of the DC wall bushing; the material parameters used for each structure of the DC wall bushing include the thermal conductivity parameters of the materials; the thermal conductivity parameters include the thermal conductivity, constant pressure heat capacity, and density of the materials; the materials are set as isotropic materials; the boundary conditions of the DC wall bushing are the convective heat transfer coefficient between the surface of the DC wall bushing structure exposed to the fluid and the fluid. Step 2) Discretize the energy conservation equation in time and space to establish a finite element equation based on the finite element simulation model for the transient thermal field of the DC wall bushing; The energy conservation equation is as follows:

[0023] Among them, is the density, c is the constant pressure heat capacity, T is the temperature, t is the time, k is the thermal conductivity, q is the heat source; The finite element equation based on the finite element simulation model for the transient thermal field of the DC wall bushing is as follows:

[0024] In the formula, is the stiffness matrix, are the thermal field distribution vectors at times n , n -1 respectively, time n is any moment, and time n -1 is the momentn At the previous moment, is the moment n of the heat source term; The stiffness matrix described is the relationship between different nodes in the discrete space at discrete times. The heat field distribution vector reflects the temperature at all grid nodes of the transient heat field finite element simulation model of the DC wall bushing. The heat source term is the linear combination of the effects of all heat sources on the heat field distribution of the DC wall bushing. All the heat sources include the heating rod of the DC wall bushing and the fluid that conducts convective heat transfer with the DC wall bushing; The linear combination can be written as:

[0025] In the formula, M is the set of all heat sources, is the moment n The heat source in the set M m of the heat generation coefficient. The heat source is the heating rod of the DC wall bushing or the fluid that conducts convective heat transfer with the DC wall bushing. When the heat source is the heating rod of the DC wall bushing, the heat generation coefficient is the heating power of the heating rod of the DC wall bushing. When the heat source is the fluid that conducts convective heat transfer with the DC wall bushing, the heat generation coefficient is the temperature of the fluid, is the heat source m of the heat source field generated by unit heat; The finite element equation based on the transient heat field finite element simulation model of the DC wall bushing can be rewritten as the following formula:

[0026] In the formula, is the heat field distribution vector at the moment k , and the moment k is a certain moment before the moment n ; Step 3) Determine the earliest moment n that affects the transient heat field distribution of the DC wall bushing at the moment k +1, ignore the power emitted by the heat source before the moment k +1, and the influence of the heat field distribution of the DC wall bushing at the moment k on the transient heat field of the DC wall bushing at the moment n , and simplify the finite element equation based on the transient heat field finite element simulation model of the DC wall bushing into a fast calculation equation for the transient heat field of the DC wall bushing. The fast calculation equation for the transient heat field of the DC wall bushing is as follows:

[0027]

[0028] Among them, is a linear combination of, calculate and store . For any moment n , is a constant value. If n -( k +1) remains unchanged, then there is no need to calculate the new unknowns on the right side of the transient heat field fast calculation equation, which simplifies the calculation process. It can be seen from the expression of the fast calculation model that when simplifying the finite element equation in this embodiment, the influence term k of the heat field distribution at the previous moment of k +1 at the earliest moment in the finite element equation on the transient heat field of the DC wall bushing at any moment is deleted. In the influence term , n - k is larger, ( g 2 -1 g 1 ) n-k is smaller. When n - k is large enough, the influence term is small enough to be ignored.

[0029] Step 4) Measure the current of the energized conductor bar (i.e., the heat-generating conductor bar) passing through the DC wall bushing and the temperature of the fluid that convectively exchanges heat with the DC wall bushing at different moments through sensors, and calculate the heat generation power of the corresponding energized conductor bar in the fast calculation equation according to the current passing through the energized conductor bar. After determining the heat generation power in the fast calculation equation, the fast calculation equation at this time is the fast calculation model (also called the fast calculation model corresponding to the fast calculation equation); Step 5) According to the fast calculation model of the transient heat field of the DC wall bushing obtained in Step 4), calculate the transient heat field distribution of the DC wall bushing at the moment n .

[0030] For a certain moment after the arbitrary moment n , repeat Step 4) to Step 5), keep n -( k +1) unchanged, and obtain the transient heat field distributions of the DC wall bushing at different moments; the calculation of the fast calculation equation of the transient heat field of the DC wall bushing depends on the heat generation power of the heat-generating conductor bar at each moment from the moment k +1 to the moment n and the temperature of the fluid that convectively exchanges heat with the DC wall bushing.

[0031] Example 1 In this embodiment, the transient thermal field of the 400 kV DC wall bushing is rapidly calculated by the above method, which specifically includes the following steps: Step 1): Use CAD software to establish a two-dimensional finite element analysis model of the DC wall bushing, partition the grid of the transient thermal field finite element simulation model of the DC wall bushing, and set the thermal conductivity parameters of the materials required for the transient thermal field calculation, including the thermal conductivity, constant pressure heat capacity, and density of each component required for calculating the temperature distribution. Set the constraint conditions required for the calculation, including the convective heat transfer coefficient between the surface of the DC wall bushing structure exposed to the fluid and the fluid.

[0032] Step 2): Set the iterative solution step size of the thermal field to 14400 s. Discretize the energy conservation equation in time and space, establish a finite element equation based on the transient thermal field finite element simulation model of the DC wall bushing, and rewrite the finite element equation.

[0033] Step 3): Determine that the moment to be solved for the transient thermal field of the DC wall bushing is the 100th step, and the number of moments affecting the transient thermal field distribution of the DC wall bushing is taken as 100 steps. Establish a rapid calculation equation for the transient thermal field of the DC wall bushing, calculate and store .

[0034] Step 4): Starting from the 0th moment, continuously measure the current passing through the conductor and the temperature of the fluid for 100 steps and calculate the heating power of the guide rod to obtain a rapid calculation model.

[0035] Step 5): According to the rapid calculation model of the transient thermal field of the DC wall bushing, calculate the transient thermal field distribution at the 100th step. Determine the next moment to be solved, continuously measure the current passing through the conductor and the temperature of the fluid for 100 steps before this moment, and calculate the transient thermal field distribution at the next moment to be solved in the same way.

[0036] The distributions of the transient thermal field of the above 400 kV DC wall bushing obtained by the above rapid calculation method and iterative calculation are shown in Figures 2(a) and 2(b) respectively. It can be seen that it takes 1.6 s to directly calculate the transient thermal field distribution of 100 steps by the rapid calculation method, and it takes 10.5 s to calculate the transient thermal field distribution of 100 steps by iterative calculation, and the calculation time is reduced by 85.8%. Figure 3 The rapid calculation results and iterative calculation results of the highest temperature of the DC wall bushing at different times are given. The maximum error between the rapid calculation and iterative calculation results is 2.32 °C, which still remains within a reasonable range and can meet the needs for monitoring the temperature of the DC wall bushing in engineering, verifying the rationality and accuracy of the method of the present invention.

[0037] In addition, the embodiment of the present invention also provides a system for implementing the above rapid calculation method of the transient thermal field of the DC wall bushing of the present invention. The system includes: Finite element equation establishment module: used to discretize the energy conservation equation in time and space, and establish a finite element equation based on the pre-established transient thermal field finite element simulation model of the DC wall-through bushing; Finite element equation simplification module: used to simplify the finite element equation to obtain a fast calculation equation for the transient thermal field finite element simulation model of the DC wall-through bushing; when simplifying the finite element equation, determine the earliest moment that affects the transient thermal field distribution of the DC wall-through bushing at any moment, and delete the influence term of the thermal field distribution at the moment before the earliest moment on the transient thermal field of the DC wall-through bushing at any moment; First calculation module: used to determine the heating coefficient in the fast calculation equation at the arbitrary moment, and obtain the fast calculation model corresponding to the fast calculation equation at the arbitrary moment; Second calculation module: used to calculate the transient thermal field distribution of the DC wall-through bushing at the arbitrary moment according to the fast calculation equation at the arbitrary moment.

[0038] The embodiment of the present invention also provides a corresponding electronic device and a computer-readable storage medium for implementing the solution provided by the embodiment of the present invention.

[0039] Among them, the device includes a memory and a processor. The memory is used to store instructions or codes, and the processor is used to execute the instructions or codes so that the device executes the transient thermal field fast calculation method of the DC wall-through bushing described in any embodiment of the present application.

[0040] The computer program is stored on the storage medium. Among them, when the computer program is executed by the processor, it implements the transient thermal field fast calculation method of the DC wall-through bushing described in any embodiment of the present application.

[0041] Obviously, the described embodiments are only partial embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not 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: the specific implementation manners of the present invention can still be modified or equivalently replaced, and any modification or equivalent replacement without departing 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 method for rapid calculation of transient thermal field of DC wall bushing, characterized in that: include: Discretize the energy conservation equation in time and space, and establish the finite element equation based on the pre-established transient thermal field finite element simulation model of the DC wall bushing; The finite element equation is simplified to obtain a fast calculation equation of a transient thermal field finite element simulation model of a DC wall bushing; when simplifying the finite element equation, the earliest time that affects the transient thermal field distribution of the DC wall bushing at any time is determined, and the influence term of the thermal field distribution at a time before the earliest time described in the finite element equation on the transient thermal field of the DC wall bushing at any time is deleted; Determine the heating coefficient in the rapid calculation equation at any time to obtain a rapid calculation model corresponding to the rapid calculation equation at any time; The transient thermal field distribution of the DC wall bushing at any time is calculated according to the fast calculation model.

2. The method for rapid calculation of transient thermal field of a DC wall bushing according to claim 1 is characterized in that: The material in the transient thermal field finite element simulation model of the DC wall bushing is set as an isotropic material, and the material parameters include the thermal conductivity parameters of the material, and the thermal conductivity parameters include the thermal conductivity, constant pressure heat capacity and density of the material; In the transient thermal field finite element simulation model of the DC wall bushing, the boundary condition of the DC wall bushing is the convection heat transfer coefficient between the surface of the DC wall bushing structure exposed in the fluid and the fluid.

3. The method for rapid calculation of transient thermal field of a DC wall bushing according to claim 1 is characterized in that: The finite element equation is as follows: in, For the moment n The thermal field distribution vector at time , For the moment k The thermal field distribution vector at time k For the moment n At some point before, and are stiffness matrices, M is the set of all heat sources, For the moment i The heat source in the set M m The heating coefficient, For heat source m The heat source field generated by unit heat.

4. The method for rapid calculation of transient thermal field of a DC wall bushing according to claim 3 is characterized in that: The heat source is a heating rod of the DC wall bushing, or a fluid that performs convection heat exchange with the DC wall bushing.

5. The method for rapid calculation of transient thermal field of a DC wall bushing according to claim 4 is characterized in that: When the heat source is the heating rod of the DC wall bushing, the heating coefficient is the heating power of the heating rod of the DC wall bushing; When the heat source is a fluid that performs convective heat exchange with the DC wall bushing, the heat generation coefficient is the temperature of the fluid.

6. The method for rapid calculation of transient thermal field of a DC wall bushing according to claim 1 is characterized in that: The quick calculation equation is as follows: in, k , n Indicates different moments, time k For the moment n At some point before, For the moment n The thermal field distribution vector at time , M is the set of all heat sources, For the moment i The heat source in the set M m The heating coefficient, and are stiffness matrices, For heat source m The heat source field generated by unit heat.

7. The method for rapid calculation of transient thermal field of a DC wall bushing according to claim 1 is characterized in that: For a certain moment after the arbitrary moment, calculating the transient thermal field distribution of the DC wall bushing at the certain moment, including: Determine the heating coefficient in the quick calculation equation at the certain moment to obtain the quick calculation equation at the certain moment; Calculating the transient thermal field distribution of the DC wall bushing at the certain moment according to the fast calculation equation at the certain moment; The time interval between the certain moment and the arbitrary moment is equal to the time interval between the arbitrary moment and the earliest moment.

8. A transient thermal field rapid calculation system for a DC wall bushing, characterized in that: include: Finite element equation building module: used to discretize the energy conservation equation in time and space, and to build the finite element equation of the transient thermal field finite element simulation model of the pre-established DC wall bushing; Finite element equation simplification module: used to simplify the finite element equation to obtain the fast calculation equation of the transient thermal field finite element simulation model of the DC wall bushing; when simplifying the finite element equation, determine the earliest time that affects the transient thermal field distribution of the DC wall bushing at any time, and delete the influence of the thermal field distribution at the moment before the earliest time mentioned in the finite element equation on the transient thermal field of the DC wall bushing at any time; A first calculation module: used to determine the heating coefficient in the fast calculation equation at any time, so as to obtain a fast calculation model corresponding to the fast calculation equation at any time; The second calculation module is used to calculate the transient thermal field distribution of the DC wall bushing at any time according to the fast calculation equation at any time.

9. An electronic device, characterized in that: include: one or more processors; a storage device having one or more programs stored thereon; When the one or more programs are executed by the one or more processors, the one or more processors implement the method for rapid calculation of transient thermal field of a DC wall bushing according to any one of claims 1 to 7.

10. A storage medium, characterized in that: A computer program is stored thereon, wherein when the computer program is executed by a processor, the method for rapidly calculating the transient thermal field of a DC wall bushing according to any one of claims 1 to 7 is implemented.

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