Converter valve water-cooling voltage-sharing electrode charged particle distribution simulation method and system

Abstract

The invention relates to a converter valve water-cooling voltage-sharing electrode charged particle distribution simulation method and system. The method comprises the following steps: constructing a three-dimensional geometric model of multiple types of voltage-sharing electrodes; constructing a charged particle multi-physics field coupling model based on the three-dimensional geometric model, wherein the coupling model comprises a flow field control equation, an electric field control equation and a particle dynamics model; simulation boundary conditions and initial conditions are set, the boundary conditions comprise flow field boundary conditions and electric field boundary conditions, and the initial conditions comprise particle release initial conditions; on the basis of the coupling model, the simulation boundary condition and the initial condition, particle tracking and distribution characteristic resolving are executed, a simulation result is obtained, and the simulation result comprises a particle motion trail, a particle capture rate and a capture area. Compared with the prior art, the method has the advantages of breaking through macroscopic monitoring limitation, realizing microcosmic dynamic quantitative analysis, analyzing a multi-field force competition mechanism, revealing a local scaling source, verifying the advantages of a multi-electrode structure, supporting optimal design and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of converter valve cooling control, and particularly relates to a method and system for simulating distribution of charged particles of a water-cooled grading electrode of a converter valve. BACKGROUND

[0002] High voltage direct current (HVDC) has become an important part of modern power systems due to its high economic benefits, small line loss, and fast regulation speed. As the core equipment of the HVDC system, the converter valve generates a large amount of heat during operation. In order to ensure that the key components such as thyristors work within the normal temperature range, an internal water cooling system using deionized water as the medium is usually used for heat dissipation. Therefore, the stable operation of the internal water cooling system is directly related to the safety of the entire HVDC system.

[0003] However, in actual engineering operation, the internal water cooling system of the converter valve often has faults such as scaling, corrosion, and water leakage on the surface of the grading electrode, which seriously threatens the reliability of the system. Research shows that the main component of the scale on the surface of the electrode is aluminum oxide (such as Al2O3 or Al(OH)3), which mainly comes from the electrochemical corrosion products of the aluminum heat sink in the cooling water circuit under the action of the corrosion current.

[0004] The scaling on the surface of the grading electrode usually has a high resistivity and is unevenly distributed on the surface of the electrode, which can cause the current to flow to the thin part of the scale or the structure connection, forming a current concentration point and generating a large current density. When the current density reaches a certain level, it can trigger an electrolytic reaction to produce ozone, which can erode the rubber sealing gasket at the root of the electrode, eventually leading to cooling water leakage; in addition, the falling of the scale can also block the fine pipeline, causing the equipment to overheat, and even causing the HVDC system to shut down in severe cases.

[0005] In order to solve the above problems, current improvement measures mainly focus on water quality control, macrostructure improvement, and chemical mechanism research. For example, by monitoring the cooling water quality in real time, using ion exchange resin to remove impurity ions, and inhibiting the entry of resin powder into the water circuit to slow down the corrosion of the aluminum heat sink from the source; or taking temporary measures such as improving the structure of the grading electrode, optimizing the material of the sealing gasket, and standardizing the installation process. Patent application CN117517431A proposes a DC transmission converter valve cooling system with grading electrode scaling early warning, which belongs to the field of converter valve cooling control, and includes a cooling pipeline for communicating with a converter valve water cooling plate. A cooling unit is provided on the cooling pipeline for cooling the cooling medium passing through the converter valve water cooling plate. The system further includes a metal ion monitoring unit, which includes a metal ion detection device connected to the cooling pipeline through a monitoring branch for monitoring the metal ion concentration information in the cooling medium in the cooling pipeline.

[0006] However, existing technologies have significant limitations, primarily in that research focuses on macroscopic water quality monitoring or static chemical corrosion product analysis, lacking in-depth study of the microscopic motion trajectory and deposition mechanism of charged particles—the direct precursors to scaling—under the coupling of complex flow fields and strong electric fields. Currently, there is no mature simulation method to quantitatively calculate the impact of different water flow velocities, electrode currents, and electrode geometries (e.g., single-electrode, multi-electrode) on the charged particle capture rate. This lack of simulation means that electrode size selection in engineering design often relies on experience, making it difficult to accurately predict particle deposition behavior under different operating conditions and avoid scaling risks from the design stage. It also fails to accurately assess the comprehensive impact of multi-physical field coupling, such as fluid drag and electric force, on the particle aggregation process towards the electrode. Therefore, there is an urgent need for a simulation analysis method that can comprehensively consider the multi-field coupling of fluid, electricity, and particles to reveal the scaling patterns of equalizing electrodes and guide the optimal design of electrode structures. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art by providing a method and system for simulating the distribution of charged particles on a water-cooled equalizing electrode of a converter valve.

[0008] The objective of this invention can be achieved through the following technical solutions: A simulation method for charged particle distribution on a water-cooled equalizing electrode of a converter valve includes the following steps: Construct three-dimensional geometric models of various types of equalizing electrodes; Based on the aforementioned three-dimensional geometric model, a multiphysics coupling model for charged particles is constructed. The coupling model includes flow field control equations, electric field control equations, and a particle dynamics model. Set simulation boundary conditions and initial conditions. The boundary conditions include flow field boundary conditions and electric field boundary conditions. The initial conditions include particle release initial conditions. Based on the aforementioned coupling model, simulation boundary conditions, and initial conditions, particle tracking and distribution characteristic calculations are performed to obtain simulation results, including particle trajectory, particle capture rate, and capture area.

[0009] Furthermore, the multi-type equalizing electrodes include at least one of single electrode, two electrode, and three electrode.

[0010] Furthermore, the flow field control equations adopt the Navier-Stokes equations to calculate the velocity vector field and pressure scalar field within the water channel; The electric field control equations employ either the Laplace equation or the Poisson equation to calculate the vector distribution of the electric field intensity around the electrodes.

[0011] Furthermore, the particle dynamics model adopts the discrete phase model in the Euler-Lagrange method to establish a force balance differential equation for a single particle, wherein the forces include fluid drag and electric field force.

[0012] Furthermore, the flow field boundary conditions include: setting the water inlet section as a velocity inlet and specifying the average flow velocity, setting the water outlet section as a pressure outlet, and setting the water pipe wall and electrode surface as non-slip static walls.

[0013] Furthermore, the electric field boundary conditions include: setting the surface of the equalizing electrode as a high-potential boundary and applying a total current, and setting the inner wall of the water pipe as an insulating boundary.

[0014] Furthermore, the initial conditions for particle release are: uniformly releasing discrete phase tracer particles at the cross-section of the waterway inlet, and assigning particle density, radius, and electrostatic charge properties.

[0015] Furthermore, the particle capture rate is the ratio of the number of particles captured by the electrode to the total number of particles released at the inlet.

[0016] Furthermore, the method also includes: By comparing simulation results under different electrode current conditions, the current value corresponding to the inflection point of the particle capture rate curve as a function of electrode current is obtained, and the current threshold of the corresponding electrode is determined based on this current value.

[0017] On the other hand, the present invention also provides a simulation system for charged particle distribution on a water-cooled equalizing electrode of a converter valve, comprising: The model building module is used to construct three-dimensional geometric models of various types of equalizing electrodes, and to construct a multi-physics coupling model of charged particles based on the three-dimensional geometric models. The coupling model includes flow field control equations, electric field control equations and particle dynamics model. The condition setting module is used to set simulation boundary conditions and initial conditions. The boundary conditions include flow field boundary conditions and electric field boundary conditions, and the initial conditions include particle release initial conditions. The simulation solution and analysis module is used to perform particle tracking and distribution characteristic calculation based on the coupled model, simulation boundary conditions and initial conditions, and obtain simulation results, including particle motion trajectory, particle capture rate and capture area; The results output module is used to output simulation results.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention represents a leap from macroscopic monitoring to quantitative analysis of microscopic dynamics: Existing technologies mostly focus on monitoring macroscopic indicators such as the conductivity of cooling water, or performing static chemical composition analysis on existing scale, failing to reveal the dynamic mechanism of the scaling process. This invention, by establishing a discrete phase particle dynamics model, is the first to quantitatively simulate the trajectory and deposition behavior of charged particles (scale precursors) in complex environments at the microscopic level. It can directly calculate the "particle capture rate" under different operating conditions, thereby elevating scale risk assessment from qualitative, empirical judgment to quantitative, scientific prediction.

[0019] 2. This invention analyzes the competition mechanism between the flow field and the electric field in a pipeline for particle motion: In actual operation, charged particles are subjected to the combined effects of fluid drag (causing them to drift with the flow) and electric field force (driving them towards the electrodes), with these two forces competing with each other. Existing design methods often struggle to accurately assess the dominance of these two forces in different regions. This invention constructs a multi-physics coupling model of charged particles in the flow field and electric field, precisely and quantitatively calculating these two key forces. It successfully reveals why particles near the pipe wall in the low-flow-velocity region are most easily captured by the electric field force, providing a precise physical model to support understanding the causes of fouling in specific areas.

[0020] 3. This invention quantitatively identifies the threshold effect of key operating parameters, guiding operation and maintenance: Existing technologies struggle to determine the level of leakage current that significantly exacerbates scaling. This invention, through simulation analysis, quantitatively identifies the "current threshold" for electric field-driven particle motion (e.g., approximately 20µA for a single-electrode structure and approximately 100µA for a three-electrode structure at an average flow velocity of 0.1 m / s). This quantitative indicator provides a clear reference line for evaluating the operating status of converter valves, contributing to the development of more scientific operation and maintenance strategies.

[0021] 4. This invention quantitatively verifies the significant advantages of multi-electrode structures in improving anti-fouling performance: In existing engineering practices, there is often a lack of quantitative evaluation criteria for whether to choose a single-electrode or multi-electrode structure. The simulation method provided by this invention can perform parallel comparative analysis of electrodes with different topologies under the same operating conditions (such as the same total leakage current and water flow velocity). The simulation results qualitatively and quantitatively confirm that multi-electrode structures (such as a three-electrode layout) effectively reduce local high-field-strength regions because the current shared by each electrode is smaller and the spatial electric field distribution generated is more uniform compared to single electrodes. This significantly increases the current threshold for triggering large-scale particle deposition in multi-electrode structures (stronger anti-fouling ability), and the growth rate of particle capture rate after exceeding the threshold is also significantly lower than that of single-electrode structures. This conclusion provides a strong theoretical basis and data support for prioritizing the selection of multi-electrode topologies in engineering design. Attached Figure Description

[0022] Figure 1 This is a flowchart of the present invention; Figure 2 This is a diagram of a single-electrode structure. Figure 3 This is a diagram showing the electric field distribution on the surface of a single electrode. Figure 4 This is a diagram of a two-electrode structure; Figure 5 This is a diagram showing the electric field distribution on the surfaces of the two electrodes. Figure 6 This is a diagram of a three-electrode structure; Figure 7 The electric field distribution on the surface of the three electrodes is shown in the diagram. Figure 8 The distribution of charged particles on a single electrode under different electrode currents; Figure 9 Diagrams showing the single-electrode particle trapping region under different electrode currents; Figure 10 The graph shows the single-electrode particle capture rate as a function of electrode current at different flow rates. Figure 11 The distribution of charged particles at the two electrodes under different electrode currents; Figure 12 Diagrams showing the particle capture regions of the two electrodes under different electrode currents; Figure 13 The graph shows the change in particle capture rate of the two electrodes with electrode current at different flow rates. Figure 14 The distribution of charged particles at the three electrodes under different electrode currents; Figure 15 Diagrams showing the three-electrode particle trapping region under different electrode currents; Figure 16 The graph shows the variation of particle capture rate with electrode current at different flow rates for the three electrodes. Detailed Implementation

[0023] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0024] like Figure 1 As shown, the simulation method for charged particle distribution on a water-cooled single electrode of a converter valve according to the present invention includes the following steps: S1. Construct a three-dimensional geometric model of multiple types of equalizing electrodes, including at least one of single electrode, two electrode, and three electrode.

[0025] S2. Based on the aforementioned three-dimensional geometric model, a multiphysics coupling model for charged particles is constructed. This coupling model includes flow field control equations, electric field control equations, and a particle dynamics model, wherein: The Navier-Stokes equations are used to calculate the velocity vector field and pressure scalar field within the waterway. The electric field control equations use either the Laplace equation or the Poisson equation to calculate the vector distribution of the electric field intensity around the electrode. The particle dynamics model adopts the discrete phase model in the Euler-Lagrange method to establish the force equilibrium differential equation for a single particle.

[0026] S3. Set simulation boundary conditions and initial conditions. The boundary conditions include flow field boundary conditions and electric field boundary conditions. The initial conditions include particle release initial conditions. The flow field boundary conditions include: setting the water inlet section as a velocity inlet and specifying the average flow velocity, setting the water outlet section as a pressure outlet, and setting the water pipe wall and electrode surface as non-slip stationary walls. The electric field boundary conditions include: setting the surface of the equalizing electrode as a high-potential boundary and applying a total current, and setting the inner wall of the water pipe as an insulating boundary; The initial conditions for particle release are: discrete phase tracer particles are uniformly released at the cross-section of the waterway inlet, and the particles are assigned density, radius and electrostatic charge properties.

[0027] S4. Based on the coupling model, simulation boundary conditions and initial conditions, perform particle tracking and distribution characteristic calculation to obtain simulation results, including particle trajectory, particle capture rate and capture area.

[0028] In a preferred embodiment, the method further includes: By comparing simulation results under different electrode current conditions, the current value corresponding to the inflection point of the particle capture rate curve as a function of electrode current is obtained, and the current threshold of the corresponding electrode is determined based on this current value.

[0029] Example 1 This embodiment provides a simulation method for charged particle distribution on a single electrode of a water-cooled converter valve, applied to a scenario of scaling risk assessment on a single electrode in a water-cooled system of a converter valve. The specific process revolves around four steps: three-dimensional geometric modeling, multiphysics coupling modeling, boundary condition setting, and particle tracking and analysis. First, a three-dimensional geometric model of a single electrode is constructed. Its purpose is to restore the physical structure of a typical single electrode in the water-cooling system of the converter valve, providing a geometric basis for subsequent simulations.

[0030] like Figure 2As shown, the single-electrode structure corresponds to a large number of pressure-equalizing single electrodes in the water-cooling system inside the converter valve. The model parameters are: water pipe inner diameter 57mm, electrode needle radius 1mm, needle tip hemispherical, and electrode needle depth into the water channel 28.5mm.

[0031] Subsequently, a multi-physics coupling model of charged particles in the flow field and electric field is constructed. This step integrates fluid dynamics, electrostatic field, and discrete phase particle dynamics models to achieve a comprehensive analysis of the effects of multiple fields on particle motion. Flow field model: Assuming the cooling medium is an incompressible Newtonian fluid, the Navier-Stokes equations are used as the governing equations for the flow field to solve for the velocity vector field and pressure scalar field within the water channel; Electric field model: The electrode surface is assumed to be at a high potential, and the inner wall of the water pipe is considered an insulating boundary. The electric field distribution is obtained by solving the Laplace equation. The mesh at the electrode ends is refined to capture the "edge effect," such as... Figure 3 As shown, when the electrode current is 2mA, the maximum electric field strength at the needle tip is approximately 834V·mm. -1 ; Particle dynamics model: The Discrete Phase Model (DPM) is adopted to establish the force balance equation of the particle in the Lagrange coordinate system, considering the coupling effect of fluid drag and electric field force.

[0032] Next, we set the simulation boundary conditions and initial conditions to ensure that the simulation is consistent with the actual working conditions: Flow field boundary: The inlet is a velocity inlet (flow velocity range 0.1m / s~5.0m / s), the outlet is a pressure outlet (relative zero pressure), and the pipe wall and electrode surface are non-slip walls; A total current excitation source is applied to the electrode surface, the inner wall of the water pipe is an insulating boundary, and 10,000 charged particles (charge number Z = 1 × 10⁻⁶) are uniformly released at the inlet section. 5 The average inlet velocity is 0.1 m / s. -1 .

[0033] Finally, particle tracking and distribution characteristic calculations are performed to quantify the single-electrode capture behavior of charged particles: Based on the steady-state flow field and electric field distribution, the particle dynamics equations are integrated over time to obtain the particle trajectory, such as... Figure 8 As shown, the particle distribution under different electrode currents is consistent with the direction of the electric field lines. Particles near the electrode region will be captured on the electrode surface, while the trajectories of particles farther from the electrode will deviate towards the electrode, and the degree of deviation increases with the increase of the electrode current. Assuming that the charged particles are uniformly distributed on the cross-section of the waterway at a sufficiently far distance from the electrode, the area on this cross-section where charged particles will be captured on the electrode surface is defined as the "capture region". Monitor the contact between the particles and the electrode surface, and calculate the ratio of the number of captured particles to the total number of particles (i.e., the capture rate). The initial coordinates of the entrance to locate the captured particles are mapped to a "capture region" cloud map on the entrance plane, such as... Figure 9 As shown, charged particles near the wall of the water pipe are more easily captured by the electrode due to their low velocity. The larger the electrode current, the stronger the electric field force, and the easier it is for the particles to gather on the electrode surface and break through the fluid boundary layer to reach the electrode surface under the action of the electric field force. Combined particles Figure 8 and Figure 9 It can be seen that charged particles at the edge of the waterway tend to accumulate along the pipe wall towards the electrode root region under the influence of the electric field, and slowly drift towards the electrode tip (where the electric field is concentrated), eventually being captured in the middle region of the electrode. The particle capture rate is defined as the ratio of the number of particles captured on the electrode surface to the total number of particles.

[0034] In a preferred embodiment, it further includes: By comparing simulation results under different electrode current conditions, the inflection point of the particle capture rate curve with current was analyzed. The critical current value at which the electric field force begins to significantly overcome the fluid drag, causing particle motion to play a dominant role and triggering a sharp increase in the capture rate was identified and defined as the "current threshold".

[0035] Specifically, by analyzing the capture rate versus current curve, the critical current in which the electric field dominates particle motion is determined, such as... Figure 10 As shown, when the electrode current is very small, the electric field force is very small compared to the flow field force, even negligible, resulting in a low capture rate of charged particles. However, the distribution of charged particles within the cross-section changes; under the influence of the electric field force, charged particles tend to aggregate around the electrode. When the electrode current exceeds the threshold, the electric field force becomes comparable to the flow field force. The larger the electrode current, the greater the electric field force, and compared to the flow field force, the greater the influence of the electric field force on particle motion. This makes it easier for charged particles to be captured by the electrode. Simultaneously, the distribution of uncaptured charged particles within the cross-section tends to aggregate near the electrode; that is, the closer to the electrode, the higher the particle concentration. When the average flow velocity is 0.1 m / s, the single-electrode current threshold is 20 μA.

[0036] Based on the results of the above simulation method, the design of equalizing voltage can be realized, thereby improving the reliability of the converter valve water cooling system.

[0037] If the above methods are implemented as 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 this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0038] Example 2 This embodiment provides a simulation method for charged particle distribution on the two electrodes of a water-cooled converter valve, which is applied to the scaling risk assessment of the main water circuit of the shielding cover in a small component water-cooling system. The process is as follows: like Figure 4 As shown, a three-dimensional geometric model of two electrodes is constructed: the two electrode structure corresponding to the main water channel at the shielding cover has the following parameters: water pipe inner diameter 57mm, electrode needle radius 1mm, two needles penetrating the water channel at 120°, needle tips embedded in the pipe wall, and the closest distance between the two needles is 1mm.

[0039] like Figure 5 As shown, in the multiphysics coupling model, the electric field distribution characteristics are: the field strength is minimum at the intersection of the two electrodes, the field strength is concentrated at both ends of the electrodes, and the maximum field strength is approximately 151 V·mm² when the current is 2 mA. -1 The remaining model settings are the same as in Example 1.

[0040] like Figure 11 As shown, the average inlet velocity is 0.1 m / s. -1 Under the influence of the electric field, the distribution trend of charged particles closely resembles the direction of electric field lines. Particles near the electrode region will be captured on the electrode surface, while particles farther from the electrode will have their trajectories shifted towards the electrode. The greater the electrode current, the stronger the electric field, and the greater the electric force experienced by the charged particles. Under the influence of the electric field, the shift of charged particles within the cross-section is also more pronounced.

[0041] like Figure 12As shown, particles on the water pipe wall are more easily captured by the electrodes due to their low velocity. The larger the electrode current, the easier it is for charged particles to accumulate towards the electrode surface under the influence of the electric field and break through the fluid boundary layer to reach the electrode surface. Charged particles at the edge of the waterway tend to accumulate along the water pipe wall towards the electrode root region under the influence of the electric field, and slowly drift towards the intersection of the two electrode needles, eventually being captured in the middle region of the electrode. The capture areas of the two electrodes are similar in size, reflecting the uniform distribution of current on the two electrodes. like Figure 13 As shown, when the average flow velocity is 0.1 m / s, the current threshold of the two electrodes is approximately 40 μA. When the electrode current is very small, the electric force is very small compared to the flow force, even negligible, resulting in a very low capture rate of charged particles. However, the distribution of charged particles within the cross-section changes; under the influence of the electric field, charged particles tend to accumulate around the electrodes. When the electrode current exceeds the threshold, the electric force becomes comparable to the flow force. The larger the electrode current, the greater the electric force, and compared to the flow force, the greater its influence on particle motion. This makes it easier for charged particles to be captured by the electrodes. Simultaneously, the uncaptured charged particles tend to accumulate near the electrodes within the cross-section; that is, the closer to the electrodes, the higher the particle concentration. Under the same electrode current, although the electric field distribution of the two-electrode structure is more uniform than that of the single-electrode structure, and the maximum field strength is smaller than that of the single-electrode structure, the contact area between the two-electrode structure and the water flow is also larger. This means that more charged particles only need to shift a smaller displacement within the cross section to be captured by the electrode. In other words, the difficulty of charged particles being captured by the electrode is reduced. Therefore, under certain conditions, the two-electrode structure has a higher adsorption rate for charged particles.

[0042] Example 3 This embodiment provides a simulation method for charged particle distribution on a three-electrode water-cooled converter valve, applied to the scaling risk assessment of the main water circuit of a water-cooling system shielding cover in a small component. The process is as follows: like Figure 6 As shown, a three-dimensional geometric model of the three electrodes is constructed: the three-electrode structure corresponding to the main water channel at the shield is constructed with the following parameters: water pipe inner diameter 57mm, electrode needle radius 1mm, the three needles are distributed at 120°, penetrate the water channel and the needle tips are embedded in the pipe wall, and the closest distance between adjacent electrodes is 1mm.

[0043] like Figure 7 As shown, in the multiphysics coupling model, the electric field distribution characteristics are: the field strength is the smallest at the intersection of the three electrodes, the field strength is concentrated at both ends of the electrodes, and the maximum field strength is about 114 V·mm when the current is 2 mA. -1 The remaining model settings are the same as in Example 1.

[0044] like Figure 14 As shown, the average inlet velocity is 0.1 m / s. -1The distribution of charged particles across the cross section under different electrode currents is shown. Under the influence of the electric field, the particle distribution trend closely resembles the direction of the electric field lines. Particles closer to the electrode region are captured on the electrode surface, while particles farther from the electrode have their trajectories shifted towards the electrode. The larger the electrode current, the stronger the electric field, and the greater the electric force experienced by the charged particles. Under the influence of the electric field, the shift of charged particles within the cross section is also more pronounced. like Figure 15 As shown, the red area represents the "capture region" for different charge numbers. Charged particles near the pipe wall are more easily captured by the electrodes due to their low velocity. The larger the electrode current, the stronger the electric field force, and the easier it is for particles to accumulate towards the electrode surface and break through the fluid boundary layer to reach the electrode surface under the influence of the electric field force. Obviously, compared to a single electrode, the three electrodes have a larger contact area with the water, so the "capture region" is also much larger than that of a single electrode. Similarly, since the water flow velocity near the pipe boundary is close to 0, boundary particles are more easily affected by the electric field and thus captured by the electrodes. This is reflected in the morphology of the "capture region," which is larger at the pipe boundary and tends to rapidly expand along the pipe wall as the electrode current increases. The size of the capture region is not significantly different among the three electrodes, indicating that the distribution of the electrode current on the three electrodes is similar. like Figure 16 As shown, when the flow velocity is 0.1 m / s, the three-electrode current threshold is approximately 100 μA. When the electrode current is very small, the electric field is much smaller than the flow field, even negligible, resulting in a low capture rate of charged particles. However, the distribution of charged particles within the cross-section changes; under the influence of the electric field, charged particles tend to aggregate around the electrodes. When the electrode current exceeds the threshold, the electric field force is comparable to the flow field force. The larger the electrode current, the greater the electric field force, and compared to the flow field force, the greater its influence on particle motion. This makes it easier for charged particles to be captured by the electrodes. Simultaneously, uncaptured charged particles tend to aggregate near the electrodes, meaning the closer to the electrodes, the higher the particle concentration. For the particle properties and specific three-electrode structure calculated by this model, when the average flow velocity is 0.1 m / s, the electrode current threshold is approximately 100 μA. The more electrodes there are, the smaller the current allocated to each electrode, and the more uniform the electric field distribution near the electrodes, the higher the electrode current threshold. Similarly, the more uniform the electric field, the greater the current after the electrode current exceeds the threshold, and the faster the capture rate of charged particles increases.

[0045] Example 4 This embodiment provides a simulation system for charged particle distribution on a water-cooled equalizing electrode of a converter valve integrated into a power equipment simulation platform, including the following modules: The model building module is used to build three-dimensional geometric models of various types of equalizing electrodes and multi-physics coupling models of charged particles. The coupling models include flow field control equations, electric field control equations and particle dynamics models, and support custom water pipe inner diameter, electrode size and layout. The condition setting module is used to set simulation boundary conditions and initial conditions. The boundary conditions include flow field boundary conditions and electric field boundary conditions, and the initial conditions include particle release initial conditions. This module supports parameter input of flow field velocity, electrode current, and particle properties, and preset boundary condition templates for typical working conditions. The solution analysis module is used to perform particle tracking and distribution characteristic calculations, including calculating particle trajectories, calculating particle capture rates, drawing capture regions, and determining current thresholds. The results output module is used to output particle capture rate, capture area and current threshold data, generate capture area cloud map and capture rate-current curve, identify current threshold, and support the comparison of simulation results of different electrode structures.

[0046] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0047] Example 5 This embodiment provides a method for assessing the scaling risk of the main water circuit of the shielding cover of a converter valve water cooling system. The scaling risk assessment method is based on the simulation results obtained by any of the simulation methods in Embodiments 1-4.

[0048] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

[0049] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for simulating charged particle distribution on a water-cooled equalizing electrode of a converter valve, characterized in that, Includes the following steps: Construct three-dimensional geometric models of various types of equalizing electrodes; Based on the aforementioned three-dimensional geometric model, a multiphysics coupling model for charged particles is constructed. The coupling model includes flow field control equations, electric field control equations, and a particle dynamics model. Set simulation boundary conditions and initial conditions. The boundary conditions include flow field boundary conditions and electric field boundary conditions. The initial conditions include particle release initial conditions. Based on the aforementioned coupling model, simulation boundary conditions, and initial conditions, particle tracking and distribution characteristic calculations are performed to obtain simulation results, including particle trajectory, particle capture rate, and capture area.

2. The method for simulating charged particle distribution on a water-cooled equalizing electrode of a converter valve according to claim 1, characterized in that, The multi-type equalizing electrodes include at least one of single electrode, two electrode, and three electrode.

3. The method for simulating charged particle distribution on a water-cooled equalizing electrode of a converter valve according to claim 1, characterized in that, The flow field control equations adopt the Navier-Stokes equations to calculate the velocity vector field and pressure scalar field within the waterway; The electric field control equations employ either the Laplace equation or the Poisson equation to calculate the vector distribution of the electric field intensity around the electrodes.

4. The method for simulating charged particle distribution on a water-cooled equalizing electrode of a converter valve according to claim 1, characterized in that, The particle dynamics model adopts the discrete phase model in the Euler-Lagrange method, and establishes a force balance differential equation for a single particle. The forces include fluid drag and electric field force.

5. The method for simulating charged particle distribution on a water-cooled equalizing electrode of a converter valve according to claim 1, characterized in that, The flow field boundary conditions include: setting the water inlet section as a velocity inlet and specifying the average flow velocity, setting the water outlet section as a pressure outlet, and setting the water pipe wall and electrode surface as non-slip static walls.

6. The method for simulating charged particle distribution on a water-cooled equalizing electrode of a converter valve according to claim 1, characterized in that, The electric field boundary conditions include: setting the surface of the equalizing electrode as a high-potential boundary and applying a total current, and setting the inner wall of the water pipe as an insulating boundary.

7. The method for simulating charged particle distribution on a water-cooled equalizing electrode of a converter valve according to claim 1, characterized in that, The initial conditions for particle release are: uniformly releasing discrete phase tracer particles at the water inlet section and assigning particle density, radius and electrostatic charge properties.

8. The method for simulating charged particle distribution on a water-cooled equalizing electrode of a converter valve according to claim 1, characterized in that, The particle capture rate is the ratio of the number of particles captured by the electrode to the total number of particles released at the inlet.

9. The method for simulating charged particle distribution on a water-cooled equalizing electrode of a converter valve according to claim 1, characterized in that, The method also includes: By comparing simulation results under different electrode current conditions, the current value corresponding to the inflection point of the particle capture rate curve as a function of electrode current is obtained, and the current threshold of the corresponding electrode is determined based on this current value.

10. A simulation system for charged particle distribution on a water-cooled equalizing electrode of a converter valve, characterized in that, include: The model building module is used to construct three-dimensional geometric models of multiple types of equalizing electrodes, and to construct a multi-physics coupling model of charged particles based on the three-dimensional geometric models. The coupling model includes flow field control equations, electric field control equations and particle dynamics model. The condition setting module is used to set simulation boundary conditions and initial conditions. The boundary conditions include flow field boundary conditions and electric field boundary conditions, and the initial conditions include particle release initial conditions. The simulation solution and analysis module is used to perform particle tracking and distribution characteristic calculation based on the coupled model, simulation boundary conditions and initial conditions, and obtain simulation results, including particle motion trajectory, particle capture rate and capture area; The results output module is used to output simulation results.

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