Capacitor temperature field analysis method and device based on harmonic voltage and storage medium

Abstract

The invention relates to the technical field of power equipment, and discloses a capacitor temperature field analysis method and device based on harmonic voltage and a storage medium, and the method comprises the steps: constructing a non-uniform loss model according to circuit parameters of a capacitor during operation based on the harmonic voltage, and the circuit parameters are used for representing the state of the capacitor; determining the loss distribution of the capacitor according to the non-uniform loss model; and determining temperature field distribution of the capacitor according to the loss distribution in combination with a thermodynamic model corresponding to the capacitor. According to the technical scheme provided by the invention, the loss distribution of the capacitor is obtained by constructing the non-uniform loss model of the capacitor working under the harmonic voltage, and the temperature field distribution of the capacitor under the harmonic voltage can be accurately obtained by combining the thermodynamic model corresponding to the capacitor, so that the accuracy of the temperature field distribution can be improved, and the reliability of the temperature field distribution is improved. And the accuracy of the relationship between the temperature field and the capacitor loss can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power equipment, and in particular to a capacitor temperature field analysis method, equipment and storage medium based on harmonic voltage. Background Art

[0002] Capacitors are important equipment commonly used in power grids. They play a role in energy storage and filtering during power transmission and distribution. However, capacitors will experience losses during operation, affecting the normal operation of the power grid.

[0003] In the related art, the loss of the capacitor can be calculated through a lumped parameter model, and the establishment of the thermal field and temperature field in the capacitor can be achieved through finite element analysis, so that the correlation between the loss distribution of the capacitor and the temperature field distribution can be determined.

[0004] However, in the case of complex voltages such as harmonic voltages, it is impossible to accurately simulate the temperature field of the capacitor, and thus it is impossible to accurately obtain the relationship between the temperature field and the capacitor loss. Summary of the invention

[0005] Based on this, in order to address the problem that the temperature field of the capacitor cannot be accurately simulated for complex voltages such as harmonic voltages, and thus the relationship between the temperature field and the capacitor loss cannot be accurately obtained, a capacitor temperature field analysis method, device and storage medium based on harmonic voltage are proposed.

[0006] In a first aspect, a capacitor temperature field analysis method based on harmonic voltage is provided, the method comprising:

[0007] constructing a non-uniform loss model according to circuit parameters of the capacitor when it operates based on the harmonic voltage, wherein the circuit parameters are used to represent the state of the capacitor;

[0008] Determining a loss distribution of the capacitor according to the non-uniform loss model;

[0009] According to the loss distribution and in combination with a thermodynamic model corresponding to the capacitor, the temperature field distribution of the capacitor is determined.

[0010] Optionally, determining the temperature field distribution of the capacitor according to the loss distribution in combination with a thermodynamic model corresponding to the capacitor includes:

[0011] Constructing the thermodynamic model corresponding to the capacitor, wherein the first surface and the second surface of the medium in the thermodynamic model are both provided with polar plates, the medium includes a plurality of temperature elements, and the first surface and the second surface are parallel;

[0012] The temperature field distribution of the capacitor is generated according to the loss distribution and in combination with the temperature element.

[0013] Optionally, generating the temperature field distribution of the capacitor according to the loss distribution and in combination with the temperature element includes:

[0014] Determining, according to the plate loss density of the plate in the thermodynamic model, a first amount of heat transmitted by the medium in a first direction, wherein the first direction is a direction from the first surface to the second surface;

[0015] determining, according to a dielectric loss density of the medium, a second amount of heat transmitted by the medium in a second direction, the second direction being perpendicular to the first direction;

[0016] The temperature field distribution is generated according to the first heat amount and the second heat amount.

[0017] Optionally, the temperature field distribution includes: a medium temperature field distribution and a plate temperature field distribution, wherein the medium temperature field distribution is used to represent the temperature distribution of the medium, and the plate temperature field distribution is used to represent the temperature distribution of the plate;

[0018] The step of generating the temperature field distribution according to the first heat and the second heat comprises:

[0019] generating the medium temperature field distribution according to the first heat and the second heat;

[0020] Calculating according to the loss distribution, the first heat amount and the second heat amount to obtain a medium boundary temperature of the medium;

[0021] The plate temperature field distribution is generated according to the medium temperature field distribution and the medium boundary temperature.

[0022] Optionally, the calculating according to the loss distribution, the first heat, and the second heat to obtain the medium boundary temperature of the medium includes:

[0023] The medium boundary temperature is obtained by calculating the loss distribution, the first heat amount and the second heat amount according to the heat convection formula and Stefan's law.

[0024] Optionally, determining the loss distribution of the capacitor according to the non-uniform loss model includes:

[0025] Performing differentiation processing according to the non-uniform loss model to obtain a differential structure;

[0026] According to the differential structure, the loss distribution of the capacitor is obtained.

[0027] Optionally, obtaining the loss distribution of the capacitor according to the differential structure includes:

[0028] According to the differential structure, a voltage differential equation and a current differential equation of the capacitor are obtained, wherein the voltage differential equation is used to represent the plate voltage distribution of the capacitor, and the current differential equation is used to represent the plate current distribution of the capacitor;

[0029] According to the voltage differential equation and the current differential equation, the total loss, plate loss and dielectric loss of the capacitor are determined, and the total loss, the plate loss and the dielectric loss constitute the loss distribution.

[0030] Optionally, after determining the temperature field distribution of the capacitor according to the loss distribution and in combination with a thermodynamic model corresponding to the capacitor, the method further includes:

[0031] According to the loss distribution and the temperature field distribution, a corresponding relationship between the loss of the capacitor and the temperature field is determined.

[0032] In a second aspect, a capacitor temperature field analysis device based on harmonic voltage is provided, the device comprising:

[0033] A model building module, used to build a non-uniform loss model according to circuit parameters of the capacitor when it operates based on the harmonic voltage, wherein the circuit parameters are used to represent the state of the capacitor;

[0034] A loss determination module, configured to determine the loss distribution of the capacitor according to the non-uniform loss model;

[0035] The temperature field determination module is used to determine the temperature field distribution of the capacitor according to the loss distribution and in combination with the thermodynamic model corresponding to the capacitor.

[0036] Optionally, the temperature field determination module is specifically used to construct the thermodynamic model corresponding to the capacitor, the first and second surfaces of the medium in the thermodynamic model are both provided with plates, the medium includes multiple temperature elements, and the first surface and the second surface are parallel; according to the loss distribution, combined with the temperature elements, the temperature field distribution of the capacitor is generated.

[0037] Optionally, the temperature field determination module is further specifically used to determine a first amount of heat transmitted by the medium in a first direction according to the plate loss density of the plate in the thermodynamic model, the first direction being a direction from the first surface to the second surface; determine a second amount of heat transmitted by the medium in a second direction according to the medium loss density of the medium, the second direction being perpendicular to the first direction; and generate the temperature field distribution according to the first amount of heat and the second amount of heat.

[0038] Optionally, the temperature field distribution includes: a medium temperature field distribution and a plate temperature field distribution, wherein the medium temperature field distribution is used to represent the temperature distribution of the medium, and the plate temperature field distribution is used to represent the temperature distribution of the plate;

[0039] The temperature field determination module is also specifically used to generate the medium temperature field distribution according to the first heat and the second heat; calculate according to the loss distribution, the first heat and the second heat to obtain the medium boundary temperature of the medium; and generate the plate temperature field distribution according to the medium temperature field distribution and the medium boundary temperature.

[0040] Optionally, the temperature field determination module is further specifically used to obtain the medium boundary temperature by calculating the loss distribution, the first heat and the second heat according to the heat convection formula and Stefan's law.

[0041] Optionally, the loss determination module is specifically used to perform differentiation processing according to the non-uniform loss model to obtain a differential structure; and obtain the loss distribution of the capacitor according to the differential structure.

[0042] Optionally, the loss determination module is specifically used to obtain a voltage differential equation and a current differential equation of the capacitor according to the differential structure, the voltage differential equation is used to represent the plate voltage distribution of the capacitor, and the current differential equation is used to represent the plate current distribution of the capacitor; according to the voltage differential equation and the current differential equation, the total loss, plate loss and dielectric loss of the capacitor are determined, and the total loss, the plate loss and the dielectric loss constitute the loss distribution.

[0043] Optionally, the device further comprises:

[0044] The relationship determination module is used to determine the corresponding relationship between the loss of the capacitor and the temperature field according to the loss distribution and the temperature field distribution.

[0045] In a third aspect, a capacitor temperature field analysis device based on harmonic voltage is provided, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the following steps:

[0046] constructing a non-uniform loss model according to circuit parameters of the capacitor when it operates based on the harmonic voltage, wherein the circuit parameters are used to represent the state of the capacitor;

[0047] Determining a loss distribution of the capacitor according to the non-uniform loss model;

[0048] According to the loss distribution and in combination with a thermodynamic model corresponding to the capacitor, the temperature field distribution of the capacitor is determined.

[0049] In a fourth aspect, a computer-readable storage medium is provided, storing a computer program, wherein when the computer program is executed by a processor, the processor performs the following steps:

[0050] constructing a non-uniform loss model according to circuit parameters of the capacitor when it operates based on the harmonic voltage, wherein the circuit parameters are used to represent the state of the capacitor;

[0051] Determining a loss distribution of the capacitor according to the non-uniform loss model;

[0052] According to the loss distribution and in combination with a thermodynamic model corresponding to the capacitor, the temperature field distribution of the capacitor is determined.

[0053] The embodiment of the present application provides a capacitor temperature field analysis method based on harmonic voltage, by constructing a non-uniform loss model according to the circuit parameters of the capacitor when it is running based on the harmonic voltage, and determining the loss distribution of the capacitor according to the non-uniform loss model, and then determining the temperature field distribution of the capacitor according to the loss distribution and the thermodynamic model corresponding to the capacitor. By constructing a non-uniform loss model of a capacitor operating under a harmonic voltage, the loss distribution of the capacitor is obtained, and then combined with the thermodynamic model corresponding to the capacitor, the temperature field distribution of the capacitor under the harmonic voltage can be accurately obtained, thereby improving the accuracy of the temperature field distribution, and further improving the accuracy of the relationship between the temperature field and the capacitor loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0055] in:

[0056] Figure 1 A schematic flow chart of a capacitor temperature field analysis method based on harmonic voltage provided in an embodiment of the present application;

[0057] Figure 2 A schematic diagram of a non-uniform loss model is provided for an embodiment of the present application;

[0058] Figure 3 A schematic diagram of a differential structure in a capacitor is provided for an embodiment of the present application;

[0059] Figure 4 A schematic flow chart for determining the temperature field distribution of a capacitor is provided for an embodiment of the present application;

[0060] Figure 5 The present application embodiment provides a schematic diagram of a thermodynamic model;

[0061] Figure 6 A schematic diagram of a heat exchange model between a capacitor and transformer oil is provided for an embodiment of the present application;

[0062] Figure 7 An internal structure diagram of a capacitor temperature field analysis device based on harmonic voltage is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0063] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] Power capacitors are important equipment commonly used in power systems. They play the role of energy storage and filtering in the process of power transmission and distribution. They can reduce harmonics and voltage fluctuations in the system and improve the efficiency and reliability of the power system. Their operating status is related to the safety and stability of power grid operation.

[0065] When operating under industrial frequency voltage, capacitors mainly consume reactive power. However, under the action of high-order harmonic voltage and high transient voltage, their active power loss will increase rapidly, which will have an impact on the internal temperature of the capacitor, which cannot be ignored. The dielectric loss of the capacitor and the Joule loss on the metal plate constitute the main components of the active power loss of the capacitor. On the one hand, the harmonic voltage components and transient voltage components in the power grid will cause the voltage amplitude to increase. Under the joint action of high frequency and high amplitude, the dielectric loss of the capacitor will also increase; on the other hand, the complex voltage waveform has an increasing effect on the current flowing through the plates of the capacitor element, so that the plate loss will also increase. The accumulation of active power loss of the capacitor is reflected in the heating of the capacitor. The increase in loss will cause the temperature to rise, which poses severe challenges to the thermal stability and insulation life of the equipment.

[0066] At present, in the calculation of capacitor loss, most studies are still using lumped parameter models to calculate capacitor loss. A wide-band loss model of capacitors that takes into account the plate current distribution has not yet been proposed, and there is a lack of research on the calculation method of capacitor loss under non-periodic voltage. In the study of capacitor temperature field distribution, the thermal field and temperature field of the capacitor are mostly established through finite element analysis. By establishing the correlation between loss distribution and temperature field distribution, the method of analyzing the internal temperature field of the capacitor needs to be improved. The correlation between the internal temperature field distribution of the capacitor and the loss distribution characteristics as well as the voltage waveform and frequency also needs to be explored.

[0067] Therefore, the embodiment of the present application provides a capacitor temperature field analysis method based on harmonic voltage, by constructing a non-uniform loss model according to the circuit parameters of the capacitor when it is running based on the harmonic voltage, and determining the loss distribution of the capacitor according to the non-uniform loss model, and then determining the temperature field distribution of the capacitor according to the loss distribution and the thermodynamic model corresponding to the capacitor. By constructing a non-uniform loss model of a capacitor operating under a harmonic voltage, the loss distribution of the capacitor is obtained, and then combined with the thermodynamic model corresponding to the capacitor, the temperature field distribution of the capacitor under the harmonic voltage can be accurately obtained, thereby improving the accuracy of the temperature field distribution, and further improving the accuracy of the relationship between the temperature field and the capacitor loss.

[0068] Moreover, the embodiment of the present application analyzes the temperature field of non-uniform loss of capacitors under harmonic voltages based on the actual internal structure of the capacitor, based on the calculation method of capacitor loss under harmonic voltages and the basic principles of heat transfer, thereby solving the problems of difficult internal temperature measurement of capacitors and high time cost of experimental testing, and has high accuracy.

[0069] The present application embodiment provides a capacitor temperature field analysis method based on harmonic voltage, such as Figure 1 As shown, Figure 1 A schematic flow chart of a capacitor temperature field analysis method based on harmonic voltage provided in an embodiment of the present application, the capacitor temperature field analysis method based on harmonic voltage specifically comprises the following steps:

[0070] Step 101: construct a non-uniform loss model according to circuit parameters when the capacitor operates based on harmonic voltage.

[0071] The circuit parameter is used to indicate the state of the capacitor. For example, the circuit parameter may be the voltage across the capacitor during operation, or the current flowing through the capacitor. The present application embodiment does not specifically limit the circuit parameter.

[0072] Before determining the temperature field distribution of the capacitor, a non-uniform loss model corresponding to the capacitor may be constructed according to the circuit parameters corresponding to the operation of the capacitor, so that in subsequent steps, the loss distribution of the capacitor may be determined by the non-uniform loss model.

[0073] For example, see Figure 2 , Figure 2 A schematic diagram of a non-uniform loss model is provided for an embodiment of the present application, such as Figure 2 As shown, the voltage across the capacitor is U0, and the current flowing through the capacitor can be i. Moreover, the capacitor can include n differential structures, where n is a positive integer used to represent the number of differential structures, and the voltage across the nth differential structure can be U n , the current flowing through the nth differential structure can be i n .

[0074] Step 102: Determine the loss distribution of the capacitor according to the non-uniform loss model.

[0075] After the non-uniform loss model is established, the various losses occurring during the operation of the capacitor can be simulated based on the non-uniform loss model to determine the energy consumed by the capacitor through heat, so that in subsequent steps, the temperature field distribution of the capacitor can be generated based on the loss distribution of the capacitor.

[0076] Optionally, a differential process may be performed first according to the non-uniform loss model to obtain a differential structure, and then the loss distribution of the capacitor may be obtained according to the differential structure. Figure 2 As shown, the capacitor may include multiple differential structures in the non-uniform loss model, and the embodiment of the present application does not specifically limit the number of differential structures.

[0077] For example, see Figure 3 , Figure 3 A schematic diagram of a differential structure in a capacitor is provided for an embodiment of the present application, such as Figure 3 As shown, the voltage at the input of the differential structure is U, and the voltage at the output is U+dU, R m is the plate resistance per unit length in the capacitor, L m is the plate inductance per unit length in the capacitor, dU is R m and L m The voltage division formed together. The current of the input differential structure is I, and the current of the output differential structure is I+dI.

[0078] Moreover, C0 represents the geometric capacitance of the insulating body with a certain structure per unit length in the capacitor and the lossless polarization. The current flowing through C0 is i C0 , R0 is the insulation resistance per unit length in the capacitor, and the current flowing through R0 is i R0 .

[0079] In addition, under unit length, the differential structure may include a polarization loss branch consisting of k branches, and the kth branch may include a polarization capacitor C k and polarization loss resistance R k .

[0080] Furthermore, in the process of obtaining the loss distribution of the capacitor according to the differential structure, we can start from the differential segment, first obtain the voltage differential equation and current differential equation of the capacitor according to the differential structure, and then further deduce the voltage and current distribution characteristics of the capacitor based on the voltage differential equation and the current differential equation, and determine the total loss, plate loss and dielectric loss of the capacitor. The total loss, plate loss and dielectric loss together constitute the loss distribution.

[0081] Among them, the voltage differential equation is used to represent the plate voltage distribution of the capacitor, and the current differential equation is used to represent the plate current distribution of the capacitor.

[0082] For example, we can first define the parameter Z, which represents the total impedance of the capacitor dielectric per unit length. The total impedance is composed of the main capacitance, insulation resistance and polarization branch. Z = R m +jωL m , R m is the plate resistance per unit length in the capacitor, L m is the plate inductance per unit length in the capacitor, j is the imaginary unit, and ω is the angular frequency.

[0083] Similarly, the total admittance of the capacitor dielectric per unit length can be expressed by the parameter G, which is composed of the main capacitance, insulation resistance, and polarization branch. Among them, C0 represents the geometric capacitance of the insulating body with a certain structure per unit length in the capacitor and the lossless polarization, R0 is the insulation resistance per unit length in the capacitor, C i is the polarization capacitance and R i is the polarization loss resistance. There are k polarization capacitors and k polarization loss resistances. j is the imaginary unit and ω is the angular frequency.

[0084] Correspondingly, from the differential structure in the capacitor equivalent model, we can get:

[0085]

[0086] Differentiate both ends of equation (1) and equation (2) with respect to x again to obtain:

[0087]

[0088] Substituting equation (1) and equation (2) into equation (3) and equation (4) and simplifying them, we can obtain Differential equation with respect to x:

[0089]

[0090]

[0091] Solve equations (5) and (6) and substitute the boundary conditions: when x = 0, when We can obtain The analytical expression of is as follows:

[0092]

[0093] In equations (1) to (7), can be the voltage differential equation of the capacitor, can be the current differential equation of the capacitor. Z represents the total impedance of the capacitor dielectric per unit length, G represents the total admittance of the capacitor dielectric per unit length, x represents the length of the capacitor plate, l is a parameter corresponding to the length of the capacitor plate, A1 and A2 are both formula parameters, and e is the natural constant.

[0094] From equation (7), we can know the analytical expression of the voltage and current distribution on the capacitor plate when the length of the capacitor plate is l and the voltage signal is input from one end of the capacitor. It should be noted that in actual situations, the voltage input signal is mostly injected from the middle position of the plate. At this time, the capacitor can be divided into two parts, and the voltage and current distributions on both sides of the signal injection point can be calculated separately.

[0095] Furthermore, the losses of the capacitor mainly consist of plate losses and dielectric losses. Under the influence of harmonic voltage, the voltage and current distribution inside the capacitor will change, and the plate losses and dielectric losses will also increase accordingly. When calculating the losses, the total losses, plate losses, and dielectric losses at each position when the voltage is input from one side can be calculated according to the voltage differential equation and the current differential equation.

[0096] Among them, the plate losses and dielectric losses together constitute the total losses of the capacitor. Moreover, the plate losses are uneven in the capacitor, resulting in uneven distribution of the total losses in the capacitor.

[0097] For example, take a point x on the capacitor plate and calculate the loss density at the position of point x and the loss to the end of the capacitor plate (0 < x1 < l). The calculation expressions are as follows:

[0098] The plate loss density p m and the plate loss P m The expressions of are respectively:

[0099]

[0100] Dielectric loss density p d and dielectric loss P d The expressions are:

[0101]

[0102] The expression of total loss P is:

[0103]

[0104] In equations (8) to (10), R m is the plate resistance per unit length in the capacitor, I x represents the current corresponding to point x, x represents the length of the capacitor plate corresponding to point x, l is the parameter corresponding to the length of the capacitor plate, represents the voltage differential equation corresponding to point x, R0 is the insulation resistance per unit length in the capacitor, C i is the polarization capacitance and R i is the polarization loss resistance. There are k polarization capacitors and k polarization loss resistances. Re[] represents the real part of a complex number, j is the imaginary unit, ω is the angular frequency, and cos is the cosine function.

[0105] Step 103: Determine the temperature field distribution of the capacitor according to the loss distribution and the thermodynamic model corresponding to the capacitor.

[0106] After obtaining the loss distribution of the capacitor, the heat transfer of the capacitor can be analyzed based on the constructed thermodynamic model corresponding to the capacitor, so that the temperature field distribution of the capacitor can be determined based on the analysis results, and the corresponding relationship between the loss of the capacitor and the temperature field can be obtained.

[0107] Accordingly, see Figure 4 , Figure 4 A schematic flowchart for determining the temperature field distribution of a capacitor is provided for an embodiment of the present application. Step 103 may include:

[0108] Step 1031: construct a thermodynamic model corresponding to the capacitor.

[0109] Wherein, the first surface and the second surface of the medium in the thermodynamic model are both provided with pole plates, the medium includes a plurality of temperature elements, and the first surface and the second surface are parallel.

[0110] For example, see Figure 5 , Figure 5 A schematic diagram of a thermodynamic model is provided for the embodiment of the present application, such as Figure 5 As shown in Figure 2, the thermodynamic model consists of a medium and plates. The plates are distributed on the upper and lower surfaces of the medium, and the medium can include multiple temperature elements ( Figure 5The temperature on the left side of the temperature element is T d (x), the temperature on the right side of this temperature element is T d (x+dx), the temperature above and below this temperature element is T m (x), Q1 represents the heat transferred from the right side of the temperature element to the left side of the temperature element by heat conduction, Q2 represents the heat transferred from the upper and lower plates of the temperature element to the temperature element by heat conduction, p d is the dielectric loss density, p m is the loss density of the plates on both sides.

[0111] Step 1032: Generate the temperature field distribution of the capacitor according to the loss distribution and the temperature element.

[0112] After obtaining the loss distribution of the capacitor, the temperature field distribution of the capacitor can be generated by combining the temperature microelement in the thermodynamic model. The temperature field distribution can include: medium temperature field distribution and plate temperature field distribution. The medium temperature field distribution is used to represent the temperature distribution of the medium, and the plate temperature field distribution is used to represent the temperature distribution of the plate.

[0113] Optionally, the first heat transmitted by the medium in the first direction can be determined based on the plate loss density of the plate in the thermodynamic model, and then the second heat transmitted by the medium in the second direction can be determined based on the medium loss density of the medium, so that a temperature field distribution can be generated based on the first heat and the second heat.

[0114] The first direction is a direction pointing from the first surface to the second surface, and the second direction is perpendicular to the first direction.

[0115] Furthermore, in the process of generating the plate temperature field distribution, the medium temperature field distribution can be first generated based on the first heat and the second heat, and then the medium boundary temperature of the medium is obtained based on the loss distribution, the first heat and the second heat. Finally, the plate temperature field distribution is generated based on the medium temperature field distribution and the medium boundary temperature.

[0116] Among them, the medium temperature field distribution is used to represent the temperature distribution of the medium.

[0117] For example, taking the temperature element as the research object, according to the law of conservation of energy, we can get:

[0118] p d ·dx=Q1+Q2 (11)

[0119] Taking the plates on both sides of the temperature element as the research object, assuming that the upper and lower surfaces of the plates are thermal insulators, according to the law of conservation of energy, we can get:

[0120] p m ·dx=Q2 (12)

[0121] From Fourier's law we know that:

[0122] Q1=k d ·A·[T d (x+dx)-T d (x)] (13)

[0123] Q2=k m ·l·dx·[T m (x)-T d (x)] (14)

[0124] From the above formula, we can get:

[0125] k d ·A·[T d (x+dx)-T d (x)]=p d ·dx+p m ·dx (15)

[0126] Divide both sides by k d A·dx is:

[0127]

[0128] From this we can get the medium temperature field distribution T d (x):

[0129]

[0130] And because:

[0131] Q2=k m ·l·dx·[T m (x)-T d (x)]=p m ·dx (18)

[0132] From this, we can get the plate temperature field distribution T m (x):

[0133]

[0134] In equations (11) to (19), dx represents the size corresponding to the temperature element, Q1 represents the heat transferred from the right side of the temperature element to the left side of the temperature element by heat conduction, Q2 represents the heat transferred from the upper and lower plates of the temperature element to the temperature element by heat conduction, and p d is the dielectric loss density, p m is the loss density of the plates on both sides, k d , k mIt is the proportional coefficient that characterizes the thermal conductivity of the dielectric and plate materials. A is the cross-sectional area of ​​the plate perpendicular to the paper surface. l is the radial length perpendicular to the paper surface. x represents the length of the capacitor plate corresponding to point x (i.e., the temperature element). T d (x) represents the temperature on the left side of the temperature element, T d (x+dx) represents the right side temperature of the temperature element, T m (x) represents the temperature on both sides of the temperature element, T d (0) is the capacitor dielectric boundary temperature.

[0135] It should be noted that in the process of calculating the medium boundary temperature, the medium boundary temperature can be obtained by calculating the loss distribution, the first heat and the second heat according to the heat convection formula and Stefan's law.

[0136] For example, see Figure 6 , Figure 6 A schematic diagram of a heat exchange model between a capacitor and transformer oil is provided for the present application embodiment. Figure 6 As shown, the interior of the capacitor is mostly embodied as a plurality of capacitor cores connected to each other in parallel and in series, and the upper and lower surfaces of adjacent capacitor cores are tightly fitted.

[0137] In the following analysis, a capacitor core at the center of the capacitor is taken as the research object. Considering the actual situation of the capacitor element, the upper and lower surfaces of the core are set to thermal insulation conditions. The heat dissipation path is only through the curved parts on the left and right sides of the core. There are thermal convection and thermal radiation phenomena between this part and the insulating oil.

[0138] The capacitor boundary is selected as the research object. According to the law of conservation of energy, the total active power loss generated by the capacitor is equal to the energy output by the capacitor to the transformer oil in the form of heat convection and heat radiation. According to the heat convection formula and the Stefan-Boltzmann law, it can be obtained:

[0139] P=h[T d (0)-T oil ]+εAσ b [T d (0)] 4 (20)

[0140] Where P is the total loss of the capacitor, h is the convection heat transfer coefficient, ε is the blackness of the capacitor surface, A is the radiation surface area of ​​the capacitor, σ b is the Stefan-Boltzmann constant, T oil is the transformer oil temperature, T d (0) is the capacitor dielectric boundary temperature.

[0141] Correspondingly, given the total loss P, convection heat transfer coefficient h, capacitor surface blackness ε, capacitor radiation surface area A, and transformer oil temperature Toil In the case of , the capacitor dielectric boundary temperature T can be solved d (0).

[0142] Step 104: Determine the corresponding relationship between the loss of the capacitor and the temperature field according to the loss distribution and the temperature field distribution.

[0143] After obtaining the temperature field distribution and loss distribution of the capacitor, the temperature field distribution and loss distribution can be studied according to the different lengths corresponding to the capacitor plates, and the corresponding relationship between the loss of the capacitor and the temperature field can be obtained.

[0144] In summary, the embodiment of the present application provides a capacitor temperature field analysis method based on harmonic voltage, by constructing a non-uniform loss model according to the circuit parameters of the capacitor when it is running based on the harmonic voltage, and determining the loss distribution of the capacitor according to the non-uniform loss model, and then determining the temperature field distribution of the capacitor according to the loss distribution and the thermodynamic model corresponding to the capacitor. By constructing a non-uniform loss model working under harmonic voltage, the loss distribution of the capacitor is obtained, and then combined with the thermodynamic model corresponding to the capacitor, the temperature field distribution of the capacitor under the harmonic voltage can be accurately obtained, thereby improving the accuracy of the temperature field distribution, and then improving the accuracy of the relationship between the temperature field and the capacitor loss.

[0145] Moreover, the embodiment of the present application analyzes the temperature field of non-uniform loss of capacitors under harmonic voltages based on the actual internal structure of the capacitor, based on the calculation method of capacitor loss under harmonic voltages and the basic principles of heat transfer, thereby solving the problems of difficult internal temperature measurement of capacitors and high time cost of experimental testing, and has high accuracy.

[0146] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0147] Corresponding to the capacitor temperature field analysis method based on harmonic voltage described in the above embodiment, a capacitor temperature field analysis device based on harmonic voltage is also provided. For the convenience of explanation, only the parts related to the embodiment of the present application are shown.

[0148] The device includes:

[0149] A model building module, for building a non-uniform loss model according to circuit parameters of the capacitor when it operates based on the harmonic voltage, wherein the circuit parameters are used to represent the state of the capacitor;

[0150] A loss determination module, used to determine the loss distribution of the capacitor according to the non-uniform loss model;

[0151] The temperature field determination module is used to determine the temperature field distribution of the capacitor according to the loss distribution and in combination with a thermodynamic model corresponding to the capacitor.

[0152] Optionally, the temperature field determination module is specifically used to construct the thermodynamic model corresponding to the capacitor, in which the first and second surfaces of the medium in the thermodynamic model are both provided with pole plates, the medium includes multiple temperature elements, and the first surface is parallel to the second surface; according to the loss distribution and in combination with the temperature elements, the temperature field distribution of the capacitor is generated.

[0153] Optionally, the temperature field determination module is also specifically used to determine a first amount of heat transmitted by the medium in a first direction based on the plate loss density of the plate in the thermodynamic model, wherein the first direction is a direction from the first surface to the second surface; determine a second amount of heat transmitted by the medium in a second direction based on the medium loss density of the medium, wherein the second direction is perpendicular to the first direction; and generate the temperature field distribution based on the first heat and the second heat.

[0154] Optionally, the temperature field distribution includes: a medium temperature field distribution and a plate temperature field distribution, wherein the medium temperature field distribution is used to represent the temperature distribution of the medium, and the plate temperature field distribution is used to represent the temperature distribution of the plate;

[0155] The temperature field determination module is also specifically used to generate the medium temperature field distribution according to the first heat and the second heat; calculate according to the loss distribution, the first heat and the second heat to obtain the medium boundary temperature of the medium; and generate the plate temperature field distribution according to the medium temperature field distribution and the medium boundary temperature.

[0156] Optionally, the temperature field determination module is further specifically used to obtain the medium boundary temperature by calculating the loss distribution, the first heat and the second heat according to the heat convection formula and Stefan's law.

[0157] Optionally, the loss determination module is specifically used to perform differentiation processing according to the non-uniform loss model to obtain a differential structure; and obtain the loss distribution of the capacitor according to the differential structure.

[0158] Optionally, the loss determination module is specifically used to obtain the voltage differential equation and the current differential equation of the capacitor according to the differential structure, the voltage differential equation is used to represent the plate voltage distribution of the capacitor, and the current differential equation is used to represent the plate current distribution of the capacitor; according to the voltage differential equation and the current differential equation, the total loss, plate loss and dielectric loss of the capacitor are determined, and the total loss, the plate loss and the dielectric loss constitute the loss distribution.

[0159] Optionally, the device further comprises:

[0160] The relationship determination module is used to determine the corresponding relationship between the loss of the capacitor and the temperature field according to the loss distribution and the temperature field distribution.

[0161] In summary, the embodiment of the present application provides a capacitor temperature field analysis device based on harmonic voltage, which constructs a non-uniform loss model according to the circuit parameters of the capacitor when it is operating based on the harmonic voltage, and determines the loss distribution of the capacitor according to the non-uniform loss model, and then determines the temperature field distribution of the capacitor according to the loss distribution and the thermodynamic model corresponding to the capacitor. By constructing a non-uniform loss model operating under harmonic voltage, the loss distribution of the capacitor is obtained, and then combined with the thermodynamic model corresponding to the capacitor, the temperature field distribution of the capacitor under the harmonic voltage can be accurately obtained, thereby improving the accuracy of the temperature field distribution, and further improving the accuracy of the relationship between the temperature field and the capacitor loss.

[0162] Figure 7 The internal structure diagram of a capacitor temperature field analysis device based on harmonic voltage is provided for the embodiment of the present application. The capacitor temperature field analysis device based on harmonic voltage can be a terminal or a server. Figure 7 As shown, the capacitor temperature field analysis device based on harmonic voltage includes a processor, a memory and a network interface connected via a system bus. Among them, the memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium of the capacitor temperature field analysis device based on harmonic voltage stores an operating system and may also store a computer program. When the computer program is executed by the processor, the processor can implement a capacitor temperature field analysis method based on harmonic voltage. The internal memory may also store a computer program. When the computer program is executed by the processor, the processor can implement a capacitor temperature field analysis method based on harmonic voltage. Those skilled in the art can understand that Figure 7 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0163] In one embodiment, a capacitor temperature field analysis device based on harmonic voltage is provided, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the following steps:

[0164] constructing a non-uniform loss model according to circuit parameters of the capacitor when it operates based on the harmonic voltage, wherein the circuit parameters are used to represent the state of the capacitor;

[0165] Determining a loss distribution of the capacitor according to the non-uniform loss model;

[0166] According to the loss distribution and in combination with a thermodynamic model corresponding to the capacitor, the temperature field distribution of the capacitor is determined.

[0167] By constructing a non-uniform loss model working under harmonic voltage, the loss distribution of the capacitor is obtained. Combined with the corresponding thermodynamic model of the capacitor, the temperature field distribution of the capacitor under harmonic voltage can be accurately obtained, thereby improving the accuracy of the temperature field distribution, and further improving the accuracy of the relationship between the temperature field and the capacitor loss.

[0168] In one embodiment, a computer-readable storage medium is provided, storing a computer program, wherein when the computer program is executed by a processor, the processor performs the following steps:

[0169] constructing a non-uniform loss model according to circuit parameters of the capacitor when it operates based on the harmonic voltage, wherein the circuit parameters are used to represent the state of the capacitor;

[0170] Determining a loss distribution of the capacitor according to the non-uniform loss model;

[0171] According to the loss distribution and in combination with a thermodynamic model corresponding to the capacitor, the temperature field distribution of the capacitor is determined.

[0172] By constructing a non-uniform loss model working under harmonic voltage, the loss distribution of the capacitor is obtained. Combined with the corresponding thermodynamic model of the capacitor, the temperature field distribution of the capacitor under harmonic voltage can be accurately obtained, thereby improving the accuracy of the temperature field distribution, and further improving the accuracy of the relationship between the temperature field and the capacitor loss.

[0173] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0174] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0175] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A capacitor temperature field analysis method based on harmonic voltage, characterized in that: The method comprises: constructing a non-uniform loss model according to circuit parameters of the capacitor when it operates based on the harmonic voltage, wherein the circuit parameters are used to represent the state of the capacitor; Determining a loss distribution of the capacitor according to the non-uniform loss model; According to the loss distribution and in combination with a thermodynamic model corresponding to the capacitor, the temperature field distribution of the capacitor is determined.

2. The capacitor temperature field analysis method based on harmonic voltage according to claim 1 is characterized in that: Determining the temperature field distribution of the capacitor according to the loss distribution and in combination with a thermodynamic model corresponding to the capacitor includes: Constructing the thermodynamic model corresponding to the capacitor, wherein the first surface and the second surface of the medium in the thermodynamic model are both provided with polar plates, the medium includes a plurality of temperature elements, and the first surface and the second surface are parallel; The temperature field distribution of the capacitor is generated according to the loss distribution and in combination with the temperature element.

3. The capacitor temperature field analysis method based on harmonic voltage according to claim 2 is characterized in that: The step of generating the temperature field distribution of the capacitor according to the loss distribution and in combination with the temperature element comprises: Determining, according to the plate loss density of the plate in the thermodynamic model, a first amount of heat transmitted by the medium in a first direction, wherein the first direction is a direction from the first surface to the second surface; determining, according to a dielectric loss density of the medium, a second amount of heat transmitted by the medium in a second direction, the second direction being perpendicular to the first direction; The temperature field distribution is generated according to the first heat amount and the second heat amount.

4. The capacitor temperature field analysis method based on harmonic voltage according to claim 3 is characterized in that: The temperature field distribution includes: a medium temperature field distribution and a plate temperature field distribution, wherein the medium temperature field distribution is used to represent the temperature distribution of the medium, and the plate temperature field distribution is used to represent the temperature distribution of the plate; The step of generating the temperature field distribution according to the first heat and the second heat comprises: generating the medium temperature field distribution according to the first heat and the second heat; Calculating according to the loss distribution, the first heat amount and the second heat amount to obtain a medium boundary temperature of the medium; The plate temperature field distribution is generated according to the medium temperature field distribution and the medium boundary temperature.

5. The capacitor temperature field analysis method based on harmonic voltage according to claim 4 is characterized in that: The calculating according to the loss distribution, the first heat and the second heat to obtain the medium boundary temperature of the medium includes: The medium boundary temperature is obtained by calculating the loss distribution, the first heat amount and the second heat amount according to the heat convection formula and Stefan's law.

6. The capacitor temperature field analysis method based on harmonic voltage according to claim 1, characterized in that: Determining the loss distribution of the capacitor according to the non-uniform loss model includes: Performing differentiation processing according to the non-uniform loss model to obtain a differential structure; According to the differential structure, the loss distribution of the capacitor is obtained.

7. The capacitor temperature field analysis method based on harmonic voltage according to claim 6, characterized in that: The step of obtaining the loss distribution of the capacitor according to the differential structure comprises: According to the differential structure, a voltage differential equation and a current differential equation of the capacitor are obtained, wherein the voltage differential equation is used to represent the plate voltage distribution of the capacitor, and the current differential equation is used to represent the plate current distribution of the capacitor; According to the voltage differential equation and the current differential equation, the total loss, plate loss and dielectric loss of the capacitor are determined, and the total loss, the plate loss and the dielectric loss constitute the loss distribution.

8. The capacitor temperature field analysis method based on harmonic voltage according to any one of claims 1 to 7, characterized in that: After determining the temperature field distribution of the capacitor according to the loss distribution and in combination with a thermodynamic model corresponding to the capacitor, the method further includes: According to the loss distribution and the temperature field distribution, a corresponding relationship between the loss of the capacitor and the temperature field is determined.

9. A capacitor temperature field analysis device based on harmonic voltage, characterized in that: The capacitor temperature field analysis device based on harmonic voltage includes: a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the capacitor temperature field analysis method based on harmonic voltage as described in any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that: A computer program is stored, and when the computer program is executed by a processor, the processor executes the steps of the capacitor temperature field analysis method based on harmonic voltage according to any one of claims 1 to 8.

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