Icing growth boundary fitting method and system

Abstract

The invention discloses an icing growth boundary fitting method and system. The method comprises the following steps: acquiring a water drop collision position; according to a result of last iteration, determining a last ice shape boundary and a control point; according to the current water drop collision position, a control point of ice shape boundary fitting is obtained; and fitting the control points and the boundary coordinates to obtain a boundary curve. In order to overcome the defects in the prior art, the invention provides an icing growth boundary fitting method which can calculate the increase thickness of lead icing in a direct current electric field, obtain position coordinates of icing growth, determine a control point of ice shape fitting according to a water drop collision position, select a proper fitting strategy to obtain an ice shape boundary and predict a rule of lead icing growth. Scientific basis and technical support are further provided for power transmission line icing prevention, line ice melting and stable and safe operation of a power grid.

Description

Technical Field

[0001] The present invention relates to the technical field of ice analysis, and in particular to an ice growth boundary fitting method and system. Background Art

[0002] The icing problem increases the mechanical load of the line and affects the electrical performance of the line, which can easily lead to the collapse and breakage of the line tower, the swaying of the line, the degradation of the insulation performance of the line, and other problems, seriously affecting the safe and stable operation of the power grid. In order to deal with the problem of icing on transmission lines, scholars from various countries have conducted extensive research and continuously improved the anti-icing capabilities by improving line design, material selection, monitoring and ice melting methods. However, despite many measures, the icing problem is still one of the main hidden dangers threatening the safety of the power grid, especially under severe climatic conditions. The degree to which the mechanical strength, electrical insulation and stability of the transmission line are affected by icing is difficult to accurately predict and control. Therefore, it is particularly important to conduct in-depth research on the boundary conditions and development laws of icing formation. Summary of the invention

[0003] In view of the above-mentioned problems, the present invention is proposed.

[0004] Therefore, the technical problem solved by the present invention is that most of the relevant research on the growth boundary of conductor ice coating is focused on the physical process of ice coating. There is no unified method for the growth of ice coating thickness and the fitting of ice coating boundary, and there is no definite research process, which is insufficient.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for fitting an ice growth boundary, comprising:

[0006] Get the water drop collision position;

[0007] According to the result of the last iteration, the last ice shape boundary and control points are determined;

[0008] According to the current water drop collision position, the control point of this ice shape boundary fitting is obtained;

[0009] The boundary curve is fitted using the control points and boundary coordinates.

[0010] As a preferred solution of the ice growth boundary fitting method described in the present invention, wherein:

[0011] A computer device comprises: a memory and a processor; the memory stores a computer program, wherein: the processor implements the steps of any one of the methods of the present invention when executing the computer program.

[0012] A computer-readable storage medium stores a computer program, wherein: when the computer program is executed by a processor, the steps of any one of the methods of the present invention are implemented.

[0013] Beneficial effects of the present invention: The ice growth boundary fitting method provided by the present invention overcomes the shortcomings of the prior art and proposes a method for ice growth boundary fitting, which can calculate the increased thickness of ice on the conductor under a DC electric field, obtain the position coordinates of the ice growth, determine the control points of the ice shape fitting according to the water droplet collision position, select an appropriate fitting strategy to obtain the ice shape boundary, predict the law of ice growth on the conductor, and further provide a scientific basis and technical support for anti-icing of transmission lines, line ice melting, and stable and safe operation of power grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0015] Figure 1 An overall flow chart of an ice growth boundary fitting method provided for the first embodiment of the present invention;

[0016] Figure 2 A flow chart of ice shape boundary calculation of an ice growth boundary fitting method provided in the first embodiment of the present invention;

[0017] Figure 3 A schematic diagram of ice shape boundary fitting in an ice growth boundary fitting method provided in a second embodiment of the present invention;

[0018] Figure 4 A schematic diagram of ice growth of surface elements of an ice growth boundary fitting method provided in a second embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0020] Example 1, reference Figure 1 , 2 , as an embodiment of the present invention, provides an ice growth boundary fitting method, comprising:

[0021] S1. Determine the last ice shape boundary and control points.

[0022] The ice shape boundary is calculated based on the result of the last iteration, and the water drop collision position used to fit the last ice shape boundary is defined as the control point of the last iteration; water drop collision refers to the water drop moving toward the wire under the influence of the external environment (wind speed, electric field force, etc.) and colliding with the wire. The water drop collision position includes the contact position between the water drop and the wire, and the contact position between the water drop and the ice shape boundary obtained after the last iteration. The control point is a point on the ice shape boundary, and the ice shape boundary is formed by the control point.

[0023] S2. Select the control point for this iteration.

[0024] Specific steps are as follows Figure 2 As shown, depending on whether the water drop collision position is within the last ice shape boundary, choose whether to keep the control points of the last iteration; if the water drop collision is within the last ice shape boundary, the control points of the last iteration will not be kept; if the water drop collision partially exceeds the last ice shape boundary, the control points of the last iteration will be kept. (If this is the initial water drop, then there is no need to judge, and the control points of this iteration can be kept directly)

[0025] According to the current water drop collision position, the control points for this ice shape boundary fitting are obtained, including: S21. Decomposition of local surface micro-elements; establishment of a micro-element analysis model for ice cover growth. When the water droplets are dense enough, the ice-covered surface will be divided into a series of micro-elements by the water droplets for subsequent calculation of ice cover thickness.

[0026] S22. Calculate the local ice coverage m i .

[0027] S23. Calculate local ice density ρ i The ice density is determined by an empirical formula, using the Bain-Gayet density formula, which fits well with the ice density measurements of fixed and rotating conductors in an icing wind tunnel.

[0028] S24. Calculate the local ice growth thickness h i ; Divide the local ice volume on each microelement by the local ice density to get the local ice volume. Divide the result by the microelement length to get the local ice growth thickness on each microelement per unit length of the conductor.

[0029] S25. Calculate the ice shape boundary coordinates; Based on the local ice thickness h calculated above i , calculate the new ice shape boundary coordinates for the next step of fitting the new ice shape boundary.

[0030] Furthermore, the selection of control points in the S2 is carried out according to the following principles: when the collision position of the water droplet in this iteration is within the boundary of the previous ice shape, the new ice covering does not completely cover the previous ice covering, and the fitting of the new ice shape still requires some control points in the previous iteration; when the collision position of the water droplet in this iteration exceeds the boundary of the previous ice shape and collides with the cylindrical wire, the ice covering of the new iteration process completely covers the previous ice shape, and the control points of the previous iteration can be discarded.

[0031] Furthermore, m in S22 i Use the following formula to calculate:

[0032] m i =β i V ∞ ωl i Δt

[0033] Among them, m i is the ice coverage on the i-th microelement, β i is the local collision coefficient on the i-th microelement, V ∞ is the inlet wind speed, ω is the liquid water content in the air, l i is the arc length of the i-th microelement, Δt is the time step of the iteration. Considering the calculation speed and cost, the time step is 1min or 2min.

[0034] Further, the ρ in S23 i Calculated using the following Bain-Gayet formula:

[0035]

[0036] Among them, v d is the velocity of the water droplet colliding with the wire, r d is the radius of the water droplet, T s is the ice surface temperature, ρ i is the local ice density on the i-th microelement, in kg / m 3 This formula is not much different from the ice density measurements of fixed and rotating conductors in an icing wind tunnel.

[0037] Further, h in S24 i Use the following formula to calculate:

[0038]

[0039] Among them, l i is the length of the local ice-covered microelement. By dividing the amount of local ice on each microelement by the local ice density, the local ice volume can be obtained. By dividing the result by the microelement length, the local ice growth thickness per unit length of the conductor can be obtained.

[0040] Furthermore, the ice shape boundary coordinate calculation method in S25 selects the midpoint of each microelement as the starting point of the microelement growth of this segment, and the ice shape grows along the normal direction. The coordinate calculation formula is as follows:

[0041]

[0042] The coordinates of the new ice shape boundary control point can be calculated by combining the position coordinates of the water droplet colliding with the ice surface with the thickness of the ice growth on the surface microelement. i_k+1 and i_k+1 are the horizontal and vertical coordinates of the new ice shape boundary, x i_k 、x i+1_k and i_k ,y i+1_k are the horizontal and vertical coordinates of the starting point of the microelement, n ix and n iy They are the infinitesimal unit normal vector n i The x and y components of h i is the local ice thickness obtained in the previous step.

[0043] S3. Fitting a boundary curve according to the control points and the boundary coordinates.

[0044] Furthermore, the fitting of the ice-shaped boundary is carried out according to the following principles: the control point is determined according to whether the water droplet collision position in this iteration is within the range of the ice-shaped boundary obtained in the previous iteration. The control points in this fitting include the coordinates of the new ice-shaped boundary obtained according to the above calculation and the control points retained from the ice-shaped boundary obtained in the previous iteration. Fitting is performed to obtain a fitting curve for the new ice-shaped boundary.

[0045] Since the simulation of the present invention uses a large number of control points, ranging from dozens to hundreds, there are several methods for fitting a large number of control points:

[0046] The curve generated by Lagrange polynomials can theoretically pass through all control points, but it is necessary to select an appropriate polynomial order: using a smaller order may result in larger errors, and using a larger order may result in oscillation problems at the boundaries.

[0047] The Bezier curve is a polynomial function of parameter t. The generated curve does not pass through the control point. As the order increases, the curve will get closer and closer to the control point.

[0048] Splines also produce smooth curves through control points, but small changes in the smoothing factor can make a big difference in the results.

[0049] Therefore, the present invention adopts a high-order polynomial fitting strategy. Using COMSOL Multiphysics finite element simulation software for fitting, it is found that when the order is above five, the fitting curve passes through the ice shape control point well and the error is very small.

[0050] On the other hand, this embodiment also provides an ice growth boundary fitting system, which includes:

[0051] The acquisition unit obtains the water drop collision position.

[0052] The fitting unit determines the last ice shape boundary and control points according to the result of the last iteration; and obtains the control points of the current ice shape boundary fitting according to the current water drop collision position.

[0053] The curve generation unit obtains the boundary curve by fitting using the control points and boundary coordinates.

[0054] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0055] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0056] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0057] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0058] Example 2, reference Figure 3 , 4 , which is an embodiment of the present invention, provides an ice growth boundary fitting method. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0059] Depending on the different collision positions of the water droplets during this iteration, the selection strategy of the ice shape boundary is also different, such as Figure 3 As shown. The black dots represent the ice boundary control points stored in the last iteration, and the black line is the corresponding fitted original ice shape. The green dots represent the collision positions of water droplets in this iteration. There may be two situations: one is that the collision positions of water droplets in this iteration are all on the ice boundary of the last iteration, Figure 2 The water droplets that collided in the middle and lower part correspond to this situation; secondly, a water droplet in this iteration exceeded the ice-covered boundary of the previous iteration and collided with the cylindrical wire. Figure 3The water droplets that collided in the upper middle correspond to this situation. The purple dots represent the boundary control points of the ice cover of this iteration calculated according to the ice cover growth thickness formula. It can be seen that the first case shows that the new ice cover does not cover the previous ice cover, and the fitting of the new ice shape still requires some control points in the previous iteration, which are represented by blue dots in the figure; the second case shows that the new ice cover has completely covered the previous ice cover, and the control points in the previous iteration can be discarded. The purple line is the new ice cover shape fitted according to this control point selection strategy.

[0060] Figure 4 The figure is a schematic diagram of ice growth of the surface microelement involved in the present invention. For the convenience of calculation, the ice-covered surface is divided into a series of microelements, and the local ice amount is calculated using the local collision rate in S21. Through microelement analysis, the analysis process can be simplified, the amount of calculation can be greatly reduced, and the fitting time can be shortened.

[0061] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for fitting ice growth boundaries, characterized in that: include: Get the water drop collision position; According to the result of the last iteration, the last ice shape boundary and control points are determined; According to the current water drop collision position, the control point of this ice shape boundary fitting is obtained; The boundary curve of the current ice cover is fitted using the control points and boundary coordinates.

2. The ice growth boundary fitting method according to claim 1, characterized in that: The water drop collision position includes the water drop moving toward the wire under the influence of the external environment and colliding with the wire when contacting the wire; The contact position of the water droplet and the wire at the ice-shaped boundary after the last iteration.

3. The ice growth boundary fitting method according to claim 2, characterized in that: According to the result of the last iteration, the ice shape boundary formed last time is obtained, and the water drop collision position used to fit the ice shape boundary last time is defined as the control point of the last iteration; The control points are points on the ice shape boundary, and the ice shape boundary is formed by the control points.

4. The ice growth boundary fitting method according to claim 3, characterized in that: The specific steps of obtaining the control point of the ice shape boundary fitting according to the current water drop collision position include: A microelement analysis model of ice growth is established, assuming that the ice surface is divided into a series of microelements by water droplets; Calculate the local ice coverage m based on the local collision coefficient i ; Calculate the ice density ρ of the local ice cover i ; Calculate the local ice growth thickness h on each microelement of the unit length wire i ; According to the calculated local ice thickness h i , calculate the coordinates of the ice shape boundary this time.

5. The ice growth boundary fitting method according to claim 4, characterized in that: The local ice coverage is expressed as: m i =b i V ∞ ωl i Δt Among them, m i is the ice coverage on the i-th microelement, β i is the local collision coefficient on the i-th microelement, V ∞ is the inlet wind speed, ω is the liquid water content in the air, l i is the arc length of the ith infinitesimal element, and Δt is the time step of the iteration; The ice density of the local ice cover is expressed as: Among them, v d is the velocity of the water droplet colliding with the wire, r d is the radius of the water droplet, T s is the ice surface temperature, ρ i is the local ice density on the i-th microelement; The local ice growth thickness is expressed as: Among them, l i is the length of the local ice-covered microelement; The ice shape boundary coordinate calculation includes selecting the midpoint of each microelement as the starting point of the microelement growth of this segment, and the ice shape grows along the normal direction. The coordinate calculation formula is as follows: Among them, x i_k+1 and i_k+1 are the horizontal and vertical coordinates of the new ice shape boundary, x i_k 、x i+1_k and i_k ,y i+1_k are the horizontal and vertical coordinates of the starting point of the microelement, n ix and n iy They are the infinitesimal unit normal vector n i The x and y components of h i is the local ice thickness obtained in the previous step.

6. The ice growth boundary fitting method according to claim 5, characterized in that: The control points of the current ice shape boundary fitting also include selecting whether to retain the control points of the previous iteration according to whether the collision position of the water droplet is within the ice shape boundary of the previous iteration; If the water drop collision this time is within the boundary of the last ice shape, the control points in the last iteration will not be retained; if the water drop collision this time partially exceeds the boundary of the last ice shape, the control points in the last iteration will be retained.

7. The ice growth boundary fitting method according to claim 6, characterized in that: The boundary curve includes fitting the coordinates of the new ice shape boundary and the control points retained from the ice shape boundary obtained in the last iteration to obtain a fitting curve of the new ice shape boundary.

8. An ice growth boundary fitting system using the method according to any one of claims 1 to 7, characterized in that: A collection unit, obtaining the collision position of water droplets; The fitting unit determines the last ice shape boundary and control points according to the result of the last iteration; and obtains the control points of the current ice shape boundary fitting according to the current water drop collision position; The curve generation unit obtains the boundary curve by fitting using the control points and boundary coordinates.

9. A computer device comprising: A memory and a processor; the memory stores a computer program, wherein the processor implements the steps of any method as claimed in claim 1 when executing the computer program.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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