A method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling.

Abstract

This invention discloses a method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling. The steps are as follows: simplification of the three-dimensional model; analysis of the heat transfer mode and path inside the frequency converter, and determination of the heat source power; extraction of the fluid domain of the water-cooling system and calculation of the inlet water flow rate of the water-air heat exchanger; calculation and extraction of the resistance and characteristic coefficients of the heat transfer characteristics of the water-air heat exchanger; importing the simulation model into ANSYS software and assigning characteristic parameters to the water-air heat exchanger; setting parameters such as the heating power and material properties of each component, and giving relevant boundary conditions; meshing and completing relevant simulation settings; and performing frequency converter temperature field simulation calculations. This method can accurately describe the heat transfer characteristics of the water-air heat exchanger, and the calculation results are closer to reality, making the temperature field simulation calculation more accurate. This method has high versatility and a wider range of applications.

Description

Technical Field

[0001] This invention relates to the field of finite element temperature field analysis, specifically to a method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling. Background Technology

[0002] Heat loss has always been a major cause of damage and failure in power devices and equipment. Overheating of electrical components reduces the reliability and lifespan of equipment. In order to improve the operating stability of frequency converters, it is very important to study the heat transfer inside the frequency converter. We need to conduct temperature field simulation analysis on the frequency converter to evaluate its thermal performance.

[0003] Inverter cooling methods are generally air cooling and water cooling. Water-air heat exchangers are commonly used cooling devices in electrical cabinets. For inverter cabinets cooled by water-air heat exchangers, the water-air heat exchanger is the most important heat exchange device inside and can directly affect the overall temperature distribution inside the inverter. Therefore, when performing temperature field simulation calculations on inverters, the description of the heat exchange performance of the water-air heat exchanger is the main factor affecting the accuracy of the simulation calculations.

[0004] The heat exchange performance parameters of a water-air heat exchanger mainly include the air resistance coefficient and heat transfer rate. Currently, when technicians perform thermal simulations of water-air heat exchangers, they generally set the air resistance and heat transfer rate as empirical constants. However, in actual operation, the air resistance and heat transfer rate of a water-air heat exchanger vary with the inlet air velocity. When the frequency converter is in a variable operating condition, the airflow of the internal fan will change over time, and the airflow and waterflow through the water-air heat exchanger will also change. If the air resistance and heat transfer rate are simply regarded as constant values, the simulation results will deviate significantly from reality, affecting the final analysis results. Summary of the Invention

[0005] This invention provides a method for analyzing the temperature of a frequency converter based on water-air heat exchanger cooling. This method can accurately extract and describe the heat transfer characteristics of the water-air heat exchanger, improve the accuracy of frequency converter temperature field simulation analysis, and is suitable for situations such as frequency converters operating under varying conditions.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling, comprising the following steps:

[0007] Step 1, 3D model simplification: Using UG 3D modeling software, construct a solid 3D model of the entire inverter cabinet, and preprocess the actual 3D model according to the simulation requirements, eliminating or simplifying components and structural features that do not affect the simulation results, and retaining the main simulation components including IGBT modules, capacitor and inductor modules, and inverter water-air heat exchanger.

[0008] Step 2: Perform internal heat generation and heat transfer analysis on the frequency converter: Identify the main heat transfer methods of the IGBTs, capacitors, inductors, and other heat-generating modules inside the cabinet. Since the temperature rise caused by thermal radiation accounts for a small proportion, the effect of thermal radiation can be ignored. Perform heat generation and heat transfer analysis on the frequency converter to determine the power of the heat source. The main heat-generating components of the frequency converter are the IGBT modules and the capacitor and inductor modules; determine their respective power loss and heat generation. A finned heat sink is installed inside the frequency converter cabinet, and the IGBT modules are mounted on the surface of the finned heat sink. Under the action of a centrifugal fan, cold air flows through the built-in air duct, is heated by the heat sink fins, enters the frequency converter's water-air heat exchanger for cooling, and is then drawn back in by the fan to complete the working cycle.

[0009] Step 3: Use SpaceClaim software to extract the fluid domain model of the water cooling system and import it into the relevant fluid calculation software of ANSYS. Then, import it into Fluent software through the interface for flow distribution simulation calculation to calculate the inlet flow rate of the inverter water-air heat exchanger: set the velocity inlet and pressure outlet according to the actual structure, set the flow monitoring at the fluid inlet of the water-air heat exchanger, and calculate the inlet flow rate of the water-air heat exchanger under different total inlet flow rates by changing the total inlet flow rate. Determine that the percentage of the water flow rate of the water-air heat exchanger to the total inlet flow rate of the water cooling system is a certain value.

[0010] Step 4: Calculate and extract the characteristic coefficients of the resistance characteristics and the characteristic coefficients of the heat transfer characteristics of the water-air heat exchanger, respectively.

[0011] Step 5: Import the 3D model of the inverter into ANSYS software and assign the parameters calculated in Step 4 to the water-air heat exchanger model.

[0012] Step 6: Adjust the size of each component model of the frequency converter, set the parameters such as the heating power and material properties of the main components in the simulation, and give the relevant boundary conditions;

[0013] Step 7, Mesh Generation: Divide the 3D model into a finite number of elements, perform mesh generation on the elements, select a suitable turbulence calculation model, ignore the influence of solar thermal radiation, altitude, gravity and other factors, set temperature monitoring points, and perform relevant initial simulation settings, including the initial temperature of the simulation model, simulation time step, etc., select a reasonable number of iteration steps and residual values, and complete the relevant simulation settings, including the selection of the solution model and the definition of convergence criteria.

[0014] Step 8: Use ANSYS software to simulate and calculate the temperature field of the frequency converter under varying operating conditions, and view the temperature field distribution of the frequency converter in the ANSYS post-processing module.

[0015] The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling includes the following steps: Step 1: Remove detailed models of components including plates, beams, and supports, such as holes and seals, and simplify them into flat plate and column models; simplify the aircraft plug mounting plate into a flat plate model; delete the aircraft plug model; simplify the busbar into a surface model that retains its external dimensions; and convert plate structures, including the main control board, secondary power distribution board, switch board, and power board, into equivalent surface models and fine-tune their dimensions to make them more reasonable.

[0016] The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling describes the following formula for calculating the temperature on both sides of the heat transfer medium during the heat conduction process in the frequency converter: Φ = kA(t1-t2), where Φ represents heat, A represents the cross-sectional area of ​​the heat transfer medium, and k represents the thermal conductivity. This can be expressed as the thermal resistance R of the heat-conducting medium. T The IGBT module's manufacturer's manual will provide specific values ​​for the relevant thermal resistance parameters.

[0017] The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling, as described above, allows for the calculation of the thermal convection process within the frequency converter using the following formula:

[0018] Φ=hA(t1-t2)

[0019] In the formula, h is the surface heat transfer coefficient, and 1 / (hA) can be expressed as the corresponding thermal resistance R. T The manufacturer of the finned heat sink inside the frequency converter can provide the specific values ​​of its thermal resistance parameters.

[0020] The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling, wherein the formula for calculating the conduction loss of the IGBT module in step 2 is as follows:

[0021]

[0022] Where T is the period, u CE For the on-state voltage drop of the IGBT module, i C δ is the collector current, and δ is the duty cycle;

[0023] The formula for calculating the switching loss of an IGBT module is:

[0024]

[0025] Where f sw U is the switching frequency. C t is the collector voltage. r Ascending time;

[0026] The formula for calculating the IGBT module turn-off loss is:

[0027]

[0028] Where t f For descent time;

[0029] The formula for calculating the core loss of the filter module in the frequency converter is:

[0030]

[0031] Where k, m, and n are the core loss coefficients, which can be found in the material handbook; the copper loss calculation formula is... Where R L For winding resistance, I av Let P be the effective value of the output current; then the total loss of the filter module is P. ∑ =P Fe +P Cu ;

[0032] The formula for calculating capacitor module losses is: in R is the effective value of the capacitor ripple current. ESR The high-frequency equivalent resistance can be found by consulting the capacitor's manufacturer's manual.

[0033] The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling involves the following steps for calculating the characteristic coefficients of the water-air heat exchanger's resistance characteristics: The physical model of the water-air heat exchanger is imported into the relevant fluid calculation software ANSYS, and the inlet air flow rate q of the water-air heat exchanger is changed... i Calculate the flow resistance p of air passing through the water-air heat exchanger under the corresponding conditions. i Based on the actual area of ​​the water-air heat exchanger, the inlet air flow rate is converted into the corresponding inlet air velocity v. i The integrated results yield the data set f(v,p)=(v i ,p i ), (i = 1, 2, 3...m), where m is determined according to the actual situation of the project; use the function p = a + bv + cv 2 Fit f(v,p), where a, b, and c are constants, and calculate using the following formula:

[0034]

[0035] Solve the formula to obtain the values ​​of parameters a, b, and c, and substitute them into the function p = a + bv + cv 2 The curve in the middle is the VP characteristic curve of the water-air heat exchanger.

[0036] The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling involves the following steps for calculating the characteristic coefficients of the water-air heat exchanger's heat transfer characteristics: Based on the actual structure, relevant parameters of the water-air heat exchanger are set in the HTRI software, including the base tube specifications and arrangement, fin size and density, chilled water flow rate and inlet / outlet temperature, air pressure, and other relevant parameters. Then, different flow velocities (v) are calculated. i Under the corresponding conditions, the heat transfer coefficient h of the water-air heat exchanger i The size of the data, combined, yields the dataset g(v,h)=(v i ,h i ), (i = 1, 2, 3...n), where n is determined according to the actual situation of the project; use the function h = x + yv + zv 2 Fit g(v,p), where x, y, and z are constants, and calculate using the following formula:

[0037]

[0038] Solve the formula to obtain the values ​​of parameters x, y, and z, and substitute them into the function h = x + yv + zv 2 The curve in the middle is the VH characteristic curve of the water-air heat exchanger.

[0039] The technical advantages of this invention are as follows: By calculating multiple sets of data on air flow resistance and heat transfer coefficient of a water-air heat exchanger under different inlet air velocity conditions, and using curve fitting, the vp and vh characteristic curves of the water-air heat exchanger are obtained. These two curves can accurately describe the flow resistance and heat exchange characteristics of the water-air heat exchanger. The characteristic parameters in these curves are then applied to the water-air heat exchanger model using finite element software for calculation. When the frequency converter is operating under variable conditions or its internal fan power is time-varying, this method has higher simulation accuracy, the calculation results are closer to reality, and it has higher versatility and a wider range of applications. Attached Figure Description

[0040] Figure 1 This is a flowchart of the analytical method of the present invention;

[0041] Figure 2 This is a schematic diagram of assigning parameters to a water-air heat exchanger in ANSYS. Detailed Implementation

[0042] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0043] Reference Figure 1 As shown, the present invention discloses a method for analyzing the temperature of a frequency converter based on water-air heat exchanger cooling, which is carried out according to the following steps.

[0044] Step 1: Simplify the 3D model.

[0045] Using UG 3D modeling software, a solid 3D model of the entire inverter cabinet was constructed. Based on simulation requirements, the actual 3D model was preprocessed, removing or simplifying components and structural features that do not affect the simulation results, while retaining the main components for simulation. Details such as holes and seals in components like plates, beams, and supports were removed and simplified into flat or cylindrical models. The aircraft mounting plate was simplified to a flat plate, and the aircraft mounting plate model was deleted. Busbars were simplified into surfaces, retaining their external dimensions. Board structures such as the main control board, secondary distribution board, switchboard, and power supply board were equivalent to surfaces, and their dimensions were fine-tuned for greater accuracy.

[0046] Step 2: Perform internal heat generation and heat transfer analysis on the frequency converter to determine the power loss of each heat-generating device in the frequency converter and clarify the heat transfer mode and path.

[0047] Heat generation and transfer were analyzed in the frequency converter. The main heat-generating components of the frequency converter are the IGBT modules and the capacitor and inductor modules, and their respective power losses were determined. A finned heat sink is installed inside the frequency converter cabinet, and the IGBT modules are mounted on the surface of the finned heat sink. Under the action of a centrifugal fan, cool air flows through the built-in air duct, is heated by the heat sink fins, enters the water-air heat exchanger for cooling, and is then drawn back in by the fan, completing the working cycle.

[0048] In step 2, the main heat transfer methods inside the frequency converter are conduction and convection, while thermal radiation is ignored. For the heat conduction process within the frequency converter, the temperatures on both sides of the heat-conducting medium are calculated using the following formula:

[0049] Φ=kA(t1-t2)

[0050] Where Φ represents heat, A represents the cross-sectional area of ​​the heat-conducting medium, and k represents the thermal conductivity. This can be expressed as the thermal resistance R of the heat-conducting medium. T The IGBT module's manufacturer's manual will provide specific values ​​for the relevant thermal resistance parameters.

[0051] The heat convection process in the frequency converter can be calculated using the following formula: Φ=hA(t1-t2), where h is the surface heat transfer coefficient. This can be expressed as the corresponding thermal resistance R. T The manufacturer of the finned heat sink inside the frequency converter can provide the specific values ​​of its thermal resistance parameters.

[0052] The formula for calculating the conduction loss of an IGBT module is: Where T is the period, u CE For the on-state voltage drop of the IGBT module, i C δ is the collector current, and δ is the duty cycle.

[0053] The formula for calculating the switching loss of an IGBT module is: Where f swU is the switching frequency. C t is the collector voltage. r The rising time.

[0054] The formula for calculating the IGBT module turn-off loss is: Where t f This refers to the descent time.

[0055] The formula for calculating the core loss of the filter module in the frequency converter is: Where k, m, and n are the core loss coefficients, which can be found in the material handbook; the copper loss calculation formula is... Where R L For winding resistance, I av Let P be the effective value of the output current; then the total loss of the filter module is P. ∑ =P Fe +P Cu .

[0056] The formula for calculating capacitor module losses is: in R is the effective value of the capacitor ripple current. ESR The high-frequency equivalent resistance can be found by consulting the capacitor's manufacturer's manual.

[0057] Step 3: Use SpaceClaim software to extract the fluid domain model of the inverter water cooling system and import it into the relevant fluid calculation software of ANSYS. Then, import it into Fluent software through the interface for flow distribution simulation calculation. Calculate the inlet flow rates of the water-air heat exchanger when the total inlet flow rate is 5, 10, 15, 20, 25, 30, 35, and 40 L / min, which are 0.9, 1.8, 2.8, 3.8, 4.8, 5.8, 6.9, and 7.9 L / min, respectively. It can be determined that the percentage of the water-air heat exchanger inlet flow rate to the total inlet flow rate is 19%. Therefore, when the total inlet flow rate of the inverter is known, the inlet flow rate of the water-air heat exchanger can be calculated.

[0058] Step 4: Calculate and extract the characteristic coefficients of the resistance characteristics and the characteristic coefficients of the heat transfer characteristics of the water-air heat exchanger.

[0059] Step 4(a): The flow resistance of the water-air heat exchanger under different inlet air flow rates is calculated using Fluent software, and the data is fitted into a function curve to describe the air resistance coefficient of the water-air heat exchanger. This step imports the physical model of the water-air heat exchanger into ANSYS software, and the flow resistance is determined by changing the inlet air flow rate q. i Calculate the flow resistance p of air passing through the water-air heat exchanger under the corresponding conditions. i Based on the actual area of ​​the water-air heat exchanger, the inlet air flow rate is converted into the corresponding inlet air velocity v. iThe integrated results yield the data set f(v,p)=(v i ,p i ), (i = 1, 2, 3...m), where m is determined according to the actual situation of the project; use the function p = a + bv + cv 2 Fit f(v,p), where a, b, and c are constants, and calculate using the following formula:

[0060]

[0061] Solve the formula to obtain the values ​​of parameters a, b, and c, and substitute them into the function p = a + bv + cv 2 The curve in the middle is the VP characteristic curve of the water-air heat exchanger.

[0062] Step 4(b): Using HTRI software, calculate the heat transfer coefficient of the water-air heat exchanger under different wind speed conditions by inputting relevant parameters of the water-air heat exchanger, and fit the data into a function curve to describe the heat transfer coefficient of the water-air heat exchanger. In this step, based on the actual structure, set the relevant parameters of the water-air heat exchanger in the HTRI software, including the base tube specifications and arrangement, fin size and density, cold water flow rate and inlet / outlet temperature, wind pressure, and other relevant parameters, and calculate the heat transfer coefficient at different flow velocities v. i Under the corresponding conditions, the heat transfer coefficient h of the water-air heat exchanger i The size of the data, combined, yields the dataset g(v,h)=(v i ,h i ), (i = 1, 2, 3...n), where n is determined according to the actual situation of the project; use the function h = x + yv + zv 2 Fit g(v,p), where x, y, and z are constants, and calculate using the following formula:

[0063]

[0064] Solve the formula to obtain the values ​​of parameters x, y, and z, and substitute them into the function h = x + yv + zv 2 The curve in the middle is the VH characteristic curve of the water-air heat exchanger.

[0065] Step 5: Import the complete 3D model of the frequency converter into ANSYS software, and assign the relevant parameters calculated in Step 4 to the water-air heat exchanger model, such as... Figure 2 As shown.

[0066] Step 6: Set the parameters such as the heating power and material properties of each component of the simulation main body, and give the corresponding boundary conditions of the system.

[0067] Step 7, Mesh generation and complete relevant simulation settings: Divide the 3D model into a finite number of element volumes, mesh the element volumes, and complete relevant simulation settings including the selection of the solution model and the definition of convergence criteria;

[0068] Step 8: Perform temperature field simulation calculations for the frequency converter in ANSYS software, and view the temperature field distribution of the frequency converter in the post-processing module.

[0069] This invention is not limited to the above-described preferred embodiments. Any person skilled in the art can derive other variations and improvements based on the inspiration of this invention. However, regardless of any changes in form, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling, characterized in that: Includes the following steps Step 1: Use UG 3D modeling software to construct a solid 3D model of the entire inverter cabinet, perform preprocessing, remove or simplify components and structural features that do not affect the simulation results, and retain the main simulation components including IGBT modules, capacitor and inductor modules, and water-air heat exchangers. Step 2: Identify the main heat transfer methods of the IGBTs and capacitor / inductor modules inside the cabinet, perform heat generation and heat transfer analysis on the inverter, and determine the power of the heat source. Step 3: Use SpaceClaim software to extract the fluid domain model of the water cooling system and import it into ANSYS software. Then, import it into Fluent software through the interface for flow distribution simulation calculation. Set the velocity inlet and pressure outlet according to the actual structure. Set the flow monitoring at the fluid inlet of the water-air heat exchanger. Calculate the water flow through the water-air heat exchanger under the corresponding conditions by changing the size of the total inlet flow. Determine the percentage of the water flow of the water-air heat exchanger to the total inlet flow of the water cooling system as a certain value. Step 4: Calculate and extract the characteristic coefficients of the resistance characteristics and the characteristic coefficients of the heat transfer characteristics of the water-air heat exchanger, respectively. Step 5: Import the 3D model of the inverter into ANSYS software and assign the parameters calculated in Step 4 to the water-air heat exchanger model. Step 6: Set the heating power and material property parameters of the main components in the simulation, and give the relevant boundary conditions; Step 7: Divide the 3D model into a finite number of element bodies, mesh the element bodies, and complete the simulation settings, including the selection of the solution model and the definition of the convergence criteria. Step 8: Use ANSYS software to simulate and calculate the temperature field of the frequency converter under varying operating conditions, and view the temperature field distribution of the frequency converter in the ANSYS post-processing module.

2. The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling according to claim 1, characterized in that, In step 1, detailed models of holes and seals in components including plates, beams, and supports are removed and simplified into flat plate and column models; the aircraft plug mounting plate is simplified into a flat plate model; the aircraft plug model is deleted; the busbar is simplified into a surface model that retains its external dimensions; and plate structures including the main control board, secondary power distribution board, switch board, and power board are equivalent to surface models.

3. The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling according to claim 1, characterized in that, In a frequency converter, the temperature across the heat transfer medium during heat conduction is calculated using the formula Φ = kA(t1 - t2), where Φ represents the amount of heat, A is the cross-sectional area of ​​the heat transfer medium, and k is the thermal conductivity. R represents the thermal resistance of the heat-conducting medium. T .

4. The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling according to claim 1, characterized in that, The heat convection process in the frequency converter is calculated by the formula Φ=hA(t1-t2), where h is the surface heat transfer coefficient and 1 / (hA) represents the corresponding heat transfer resistance.

5. A method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling, as described in claim 1, 2, 3, or 4, characterized in that, The formula for calculating the conduction loss of the IGBT module in step 2 is as follows: In the formula, T is the period, u CE For the on-state voltage drop of the IGBT module, i C δ is the collector current, and δ is the duty cycle; The formula for calculating the switching loss of an IGBT module is: In the formula f sw U is the switching frequency. C t is the collector voltage. r Ascending time; The formula for calculating the turn-off loss of an IGBT module is: In the formula t f For descent time; The formula for calculating the core loss of the filter module in the frequency converter is as follows: In the formula, k, m, and n are the core loss coefficients; the copper loss calculation formula is as follows: Where R L For winding resistance, I av This is the effective value of the output current; The total loss of the filter module is P ∑ =P Fe +P Cu The formula for calculating capacitor module losses is: in R is the effective value of the capacitor ripple current. ESR It is the high-frequency equivalent resistance.

6. The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling according to claim 5, characterized in that, The characteristic coefficient calculation steps for the resistance characteristics of the water-air heat exchanger are as follows: Import the physical model of the water-air heat exchanger into the relevant fluid calculation software ANSYS, and change the inlet air flow rate q of the water-air heat exchanger... i Calculate the flow resistance p of air passing through the water-air heat exchanger under the corresponding conditions. i Based on the actual area of ​​the water-air heat exchanger, the inlet air flow rate is converted into the corresponding inlet air velocity v. i The integrated results yield the data set f(v,p)=(v i ,p i ), where i = 1, 2, 3...m; using the function p = a + bv + cv 2 Fit f(v,p), where a, b, and c are constants, and calculate using the following formula: Solve the formula to obtain the values ​​of parameters a, b, and c, and substitute them into the function p = a + bv + cv 2 The curve in the middle is the VP characteristic curve of the water-air heat exchanger.

7. The method for analyzing the temperature field of a frequency converter based on water-air heat exchanger cooling according to claim 5, characterized in that, The calculation steps for the characteristic coefficients of the water-air heat exchanger heat transfer characteristics are as follows: Based on the actual structure, set the water-air heat exchanger parameters in the HTRI software, including base tube specifications and arrangement, fin size and density, cold water flow rate and inlet / outlet temperature, and air pressure, and calculate the flow rate v at different flow velocities. i Under the corresponding conditions, the heat transfer coefficient h of the water-air heat exchanger i The size of the data, combined, yields the dataset g(v,h)=(v i ,h i ), i = 1, 2, 3...n; use the function h = x + yv + zv 2 Fit g(v,p), where x, y, and z are constants, and calculate using the following formula: Solve the formula to obtain the values ​​of parameters x, y, and z, and substitute them into the function h = x + yv + zv 2 The curve in the middle is the VH characteristic curve of the water-air heat exchanger.

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