Transformer magnetic core loss calculation method and system considering variable loss coefficient

Abstract

The invention provides a transformer magnetic core loss calculation method and system considering a variable loss coefficient, and the method comprises the steps: considering the influence of a high-frequency skin effect and a dynamic hysteresis loop on the iron core loss, and building a variable coefficient loss calculation formula; substituting the normalization constant into an integral form of an average value of the magnetic induction intensity in a period to obtain an equivalent frequency expression; and obtaining a generalized Steinmetz waveform coefficient formula under non-sine excitation based on the equivalent frequency expression and the variable coefficient loss calculation formula, and calculating the magnetic core loss of the nanocrystalline high-frequency transformer based on the formula.

Description

Technical Field

[0001] The invention belongs to the technical field of calculation of magnetic core loss of nanocrystalline high-frequency transformers, and in particular relates to a method and system for calculating magnetic core loss of transformers taking into account variable loss coefficients. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] With the rapid development of power electronics technology and the popularization of new materials such as nanocrystalline and amorphous alloys, high frequency has become an inevitable trend in the development of power electronics devices. High frequency devices can improve the efficiency and power density of the whole machine without affecting the operation of the equipment, and greatly reduce the weight and volume of magnetic components.

[0004] Nanocrystalline materials have small grain size, low eddy current loss and hysteresis loss. In addition, nanocrystalline materials have excellent magnetic conductivity and high magnetization strength, and gradually become the ideal material for high-frequency transformer cores. The excitation waveform in power electronic devices is generally non-sinusoidal, with large harmonic content and high operating frequency.

[0005] Core loss increases significantly with the increase of operating frequency, which greatly reduces the efficiency and reliability of the device.

[0006] Therefore, studying the core loss under non-sinusoidal high-frequency excitation and establishing an accurate and easy-to-calculate loss prediction model are of great significance for the optimization design of power electronic devices in terms of efficiency calculation, temperature rise prediction, etc.

[0007] At present, the methods for calculating core loss in engineering are mainly divided into three categories: ① Hysteresis loss model based on physical phenomena. ② Loss separation method based on the assumption that core loss can be separated. ③ Empirical formula method based on experimental data fitting.

[0008] The hysteresis loss model method is a method used to calculate and analyze the energy loss caused by hysteresis phenomenon in the process of repeated magnetization of ferromagnetic materials. The JA model and the Preisach model are two widely used mathematical models in the simulation of hysteresis characteristics of magnetic materials. The JA model was proposed by David Jiles and Michael Atherton in the 1880s. The model is based on the theory of local equilibrium magnetization intensity and considers the nonlinear and dissipative effects in the microscopic magnetization process. It can accurately simulate the hysteresis loop of ferromagnetic materials. However, the JA model makes certain assumptions and simplifications in the modeling process. In practical applications, a large number of differential equations need to be solved, which increases the complexity of the calculation. The Preisach model regards the hysteresis process as the superposition result of a series of hysteresis units (Hysteresis Operator). By adjusting the weights and switching values ​​of these hysteresis units, a complex hysteresis loop is simulated. The Preisach model predicts the hysteresis loop and loss characteristics of ferromagnetic materials with very high accuracy, and can also be extended to complex systems such as multiphase materials and composite materials. However, the Preisach model contains a large number of hysteresis units and integral operations, has a slow calculation speed, relies on a large amount of experimental data to determine the distribution function, and has high complexity. These two models have many parameters that are interrelated, and the identification process is affected by many factors, so they are not applicable in engineering calculations.

[0009] The loss separation method is based on the different physical mechanisms of core loss, which is subdivided into the following three categories: ① Hysteresis Losses ② Eddy-current Losses ③ Anomalous Losses. The core loss is the sum of these three, as shown in formula (1):

[0010] P s =P h +P e +P a (1)

[0011] Where P s is the total core loss, P h is the hysteresis loss, P e is the eddy current loss, P a Compared with the hysteresis model method, the loss separation method simplifies the iron loss analysis process and can more accurately calculate the various parts of the core loss, which helps to gain a deeper understanding of the mechanism and characteristics of the core loss. In high-frequency conditions, the classical eddy current loss is dominant, and the abnormal loss caused by the movement of the magnetic domain wall accounts for a small proportion and can be ignored. At this time, the loss separation model can be simplified to the Jordan model, that is,

[0012] P s =P h +P e (2)

[0013] However, the loss separation model is rarely used in actual calculations because it involves many parameters and the confirmation process is complicated.

[0014] The Original Steinmetz Equation (OSE) was proposed by German scholar CP Steinmetz in 1892. It is believed that the core loss is related to the excitation frequency and the peak value of the magnetic flux density, as shown in formula (3):

[0015]

[0016] Where P v is the core loss density, W / m 3 , f is the excitation voltage frequency, Hz, K, α, β are the loss parameters under sinusoidal excitation, which are related to the core characteristics. Due to the simple form of formula (3) and the few design parameters, it has gradually become the calculation formula for calculating the core loss of electromagnetic equipment such as transformers and motors. However, OSE can only calculate the iron loss under sinusoidal excitation. If it is applied to non-sinusoidal excitation, it needs to be corrected.

[0017] IGSE:

[0018] The Improved Generalized Steinmetz Equation (IGSE) believes that the core loss is not only related to the magnetic flux density change rate dB / dt, but also affected by the instantaneous value of the magnetic flux density B(t), as shown in the formula:

[0019]

[0020] Where: ΔB is the peak value of magnetic induction intensity within a magnetization period T, ΔB = B max -B min , B max , B min are the maximum and minimum values ​​of the magnetic induction intensity in a magnetization cycle. i The expression is as follows:

[0021]

[0022] Where θ is the integral angle. IGSE takes into account the magnetization process and magnetization history of the magnetic material and the influence of the magnetization reversal point on the hysteresis loop. It is suitable for the calculation of core loss under the excitation of a local small hysteresis loop.

[0023] WcSE:

[0024] The Steinmetz waveform coefficient formula (WcSE) defines the waveform coefficient λ according to the ratio of the area enclosed by the magnetic induction intensity curve and the coordinate axis in a magnetization cycle under non-sinusoidal excitation to the area under sinusoidal excitation. Multiplying the waveform coefficient λ by OSE can obtain WcSE as shown in formula (6):

[0025]

[0026] WcSE corrects OSE based on the difference between the magnetic induction intensity curves under non-sinusoidal excitation and sinusoidal excitation. In principle, it is superior to the above method. The greater the difference between the excitation voltage waveform and the sinusoidal waveform, the more the WcSE advantage in accuracy can be reflected.

[0027] Therefore, the hysteresis model method and loss separation method have clear principles and accurate calculations, but they require a large number of calculation parameters and the parameter identification process is complicated, which is not suitable for engineering practice. The empirical formula method requires fewer parameters and is easy to use. It is the most popular calculation method in practical applications.

[0028] In addition, the inventors found in their research that as the frequency increases, the core skin effect becomes more obvious, and the magnetic flux density is no longer evenly distributed in the core. At high magnetic flux density, the core hysteresis loop changes, and the change in magnetic flux density causes the loss coefficient K to change accordingly. If the loss coefficient is regarded as a constant, the calculation error will gradually increase. Figure 1 The loss coefficient K is given as a function of the magnetic flux density B m From the relationship curve, it can be seen that K and B have a nonlinear relationship. Therefore, the current calculation method using a fixed loss coefficient cannot meet the high-frequency transformer's high requirements for loss calculation, and the error is large.

[0029] In addition, the existing literature Transactions of China Electrotechnical Society, March 2023, Vol. 38, No. 5, "Improvement and Verification of Calculation Method of High-Frequency Core Loss of Nanocrystalline Materials under Non-Sinusoidal Excitation" takes into account the influence of duty cycle, which will lead to significant deviation of calculation results in actual high-frequency transformer loss calculation. In addition, the literature also proposes a correction factor to adjust its loss calculation process. Therefore, although the scheme takes into account the duty cycle and introduces the correction factor, the selection process of its correction factor is subjective. In addition, under complex working conditions, the applicability of its correction factor will be limited. Summary of the invention

[0030] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a transformer core loss calculation method taking into account a variable loss coefficient, which can effectively predict the core loss under high frequency and non-sinusoidal waveform excitation.

[0031] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0032] In a first aspect, a method for calculating transformer core loss considering a variable loss coefficient is disclosed, comprising:

[0033] Considering the influence of high-frequency skin effect and dynamic hysteresis loop on core loss, a variable coefficient loss calculation formula is established;

[0034] Substituting the normalization constant into the integral form of the average value of magnetic induction intensity in one cycle, the equivalent frequency expression can be obtained;

[0035] The generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation is obtained based on the equivalent frequency expression and the variable coefficient loss calculation formula. The core loss of nanocrystalline high-frequency transformer is calculated based on this formula.

[0036] As a further technical solution, when establishing the variable coefficient loss calculation formula, the loss coefficient K is changed with the magnetic flux density B. m The relationship curve is represented as a polynomial function:

[0037]

[0038] Where: D i is the coefficient of the loss coefficient K raised to the power of i, and K is obtained by fitting the measured values, where i=0, 1, 2, 3, 4.

[0039] As a further technical solution, the generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation is:

[0040] Among them, Pv is the core loss density.

[0041] As a further technical solution, when the non-sinusoidal excitation is square wave excitation:

[0042] Obtain the function expression of the square wave excitation voltage in one cycle and the expression of the rate of change of the magnetic induction intensity in one cycle;

[0043] Substituting the expression of the rate of change of magnetic induction intensity within one cycle into the equivalent frequency expression, the equivalent frequency under square wave excitation can be obtained;

[0044] By calculating the ratio of the area enclosed by the magnetic induction intensity curve and the coordinate axis under square wave excitation to that under sine excitation, the waveform coefficient of the square wave can be obtained;

[0045] Substituting the square wave waveform coefficient into the generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation, the generalized Steinmetz waveform coefficient formula under square wave excitation is obtained.

[0046] As a further technical solution, the generalized Steinmetz waveform coefficient formula under square wave excitation is:

[0047]

[0048] As a further technical solution, when the non-sinusoidal excitation is a triangular wave excitation:

[0049] Obtain the function expression of the triangle wave excitation in one cycle;

[0050] Then obtain the equivalent frequency of the triangle wave excitation at;

[0051] By calculating the ratio of the area enclosed by the magnetic induction intensity curve and the coordinate axis under triangular wave excitation to that under sine excitation, the waveform coefficient of the triangular wave can be obtained;

[0052] Substituting the waveform coefficient of the triangular wave into the generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation, the generalized Steinmetz waveform coefficient formula under triangular wave excitation is obtained.

[0053] As a further technical solution, the generalized Steinmetz waveform coefficient formula under triangular wave excitation is:

[0054]

[0055] In a second aspect, a transformer core loss calculation system considering a variable loss coefficient is disclosed, comprising:

[0056] The variable coefficient loss calculation formula establishment module is configured to: consider the influence of high-frequency skin effect and dynamic hysteresis loop on core loss, and establish the variable coefficient loss calculation formula;

[0057] The equivalent frequency expression calculation module is configured to: bring the normalization constant into the integral form of the average value of the magnetic induction intensity within one period, and obtain the equivalent frequency expression;

[0058] The transformer core loss calculation module is configured as follows: based on the equivalent frequency expression and the variable coefficient loss calculation formula, a generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation is obtained, and based on the formula, the core loss of the nanocrystalline high-frequency transformer is calculated.

[0059] One or more of the above technical solutions have the following beneficial effects:

[0060] The exemplary technical scheme of this embodiment conducts an in-depth analysis of the core factors that affect the core loss. Based on the Steinmetz waveform coefficient formula, it is proposed to use equivalent frequency and variable loss coefficient to improve the calculation accuracy of the Steinmetz waveform coefficient formula, and build a high-frequency non-sinusoidal nanocrystal magnetic property measurement platform based on a full-bridge inverter circuit. The generalized Steinmetz waveform coefficient formula (Generalized Waveform coefficient Steinmetz Equation, GWcSE) under non-sinusoidal excitation is obtained by numerical fitting. The calculated results are compared with the measured values ​​to verify the accuracy of the proposed model. It can effectively predict the core loss under high frequency and non-sinusoidal waveform excitation, and provides more accurate and comprehensive theoretical guidance for research and application in related fields.

[0061] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0063] Figure 1 It is a schematic diagram of the relationship between K and B;

[0064] Figure 2 It is a schematic diagram of the square wave excitation waveform and the corresponding magnetic flux density waveform;

[0065] Figure 3 It is a schematic diagram of the triangular wave excitation waveform and the corresponding magnetic flux density waveform;

[0066] Figure 4 It is a schematic diagram of the non-sinusoidal experimental measurement system;

[0067] Figure 5 This is a comparison chart of core loss density under 5kHz frequency square wave excitation;

[0068] Figure 6 This is a comparison chart of core loss density under 5kHz frequency triangle wave excitation. DETAILED DESCRIPTION

[0069] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0070] It should be noted that the terms used herein are for describing specific embodiments only and are not intended to be limiting of exemplary embodiments according to the present invention.

[0071] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0072] Embodiment 1

[0073] This embodiment discloses a method for calculating transformer core loss considering variable loss coefficient, including:

[0074] Step 1: Consider the influence of high-frequency skin effect and dynamic hysteresis loop on core loss, and establish a variable coefficient loss calculation formula;

[0075] Step 2: Substitute the normalized constant into the integral form of the average value of the magnetic induction intensity in one cycle to obtain the equivalent frequency expression;

[0076] Step 3: Based on the equivalent frequency expression and the variable coefficient loss calculation formula, the generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation is obtained, and the core loss of the nanocrystalline high-frequency transformer is calculated based on this formula.

[0077] In step 1 of this embodiment: considering that the high-frequency transformer has high requirements for loss calculation, a variable coefficient loss calculation formula is established here to consider the influence of high-frequency skin effect and dynamic hysteresis loop on core loss. Figure 1 The curve in can be characterized by the curve fitting tool as a 4-degree polynomial function, that is,

[0078]

[0079] Where: D i (i=0, 1, 2, 3, 4) is the coefficient of the i-th power of the loss coefficient K, and K is obtained by fitting the measured value.

[0080] The specific fitting process is:

[0081] Experimental measurement: First, by actually measuring the core loss data at different frequencies and different maximum magnetic flux densities, measurements are performed under multiple different frequency and magnetic flux density conditions to ensure that the data points obtained are sufficient.

[0082] Calculation model selection: Select the GWcSE calculation model based on the actual loss distribution. If more complex situations need to be considered, more high-order terms or nonlinear terms can be introduced.

[0083] Data fitting: The measured loss value P core , frequency f and maximum magnetic flux density B maxSubstitute into the loss model formula and use numerical fitting method (least square method) to determine the unknown coefficients.

[0084] Calculation error: Calculate the theoretical loss value through the fitted formula and compare it with the actual measured value to calculate the error. If the error is large, you need to readjust the model or add more test data points to improve the fitting accuracy.

[0085] Iterative optimization: By repeatedly adjusting the fitting method and loss model, the fitting results are optimized and the accurate coefficients are finally determined.

[0086] Among them, the least squares fitting process is specifically as follows:

[0087] The least squares method obtains the optimal coefficient by minimizing the sum of squares of the errors between the theoretical calculation value and the experimental measurement value. Assume that there are N sets of experimental data (B m,i ,P new,i ), then the fitting error of each set of data can be written as:

[0088]

[0089] The coefficients D4, D3, D2, D1, and D0 are fitted by minimizing the total sum of squared errors, i.e.:

[0090]

[0091] The least squares method is used to solve the problem by numerical methods (linear regression or matrix methods). The problem is expressed in matrix form:

[0092]

[0093] The problem can be written as a matrix equation:

[0094] Y=XD

[0095] The least squares solution is of the form:

[0096] D=(X T X) -1 X T Y

[0097] This formula can be used to calculate the values ​​of each coefficient.

[0098] After obtaining the fitting coefficients, substitute them into the original formula K(B m ), the final core loss calculation formula can be obtained. Then the actual core loss P is calculated by correcting the frequency f. core .

[0099] The calculation method of the sub-technical solution of this embodiment does not include the duty cycle in the analysis. The calculation waveforms of the sub-technical solution of this embodiment are all based on symmetrical voltage excitation, and the influence of the duty cycle on the waveform and loss is not considered. Considering that the duty cycle will cause significant deviation in the calculation results in the actual high-frequency transformer loss calculation, this paper makes a reasonable simplification of the duty cycle.

[0100] Difference between correction coefficient and equivalent frequency: This embodiment of the technical solution proposes the concept of equivalent frequency to perform relevant loss calculations. Although both the correction coefficient and the equivalent frequency are intended to compensate or adjust the loss, their calculation principles and mathematical derivation processes are essentially different.

[0101] The calculation accuracy of several steimize correction formulas under non-sinusoidal excitation is compared. Among the various correction formulas of SE, under triangular wave voltage excitation, the calculation results of MSE and IGSE are closer to the measured values, but the WcSE calculation curve is closest to the measured value curve. Under square wave voltage excitation, there will be a large deviation between the MSE and IGSE calculated values ​​and the measured values. WcSE is more accurate than OSE correction under non-sinusoidal excitation, and the greater the difference between the excitation waveform and the sinusoidal waveform, the higher the correction accuracy of WcSE compared with other methods. An empirical formula with simple structure and high accuracy is needed to solve the problem of predicting the core loss under non-sinusoidal excitation. WcSE is most suitable for calculating the loss of nanocrystalline cores under non-sinusoidal voltage excitation. Therefore, this embodiment chooses to make improvements based on WcSE. At this time, the core calculation formula under non-sinusoidal excitation is:

[0102]

[0103] The core loss is directly related to the macroscopic remagnetization rate dM / dt, which is positively correlated with dB / dt. The empirical loss parameter frequency in formula (6) must be replaced by the physical loss parameter:

[0104]

[0105] in is the average value of magnetic induction intensity B in one cycle, ΔB=B max -B min , B max , B min They are the maximum and minimum values ​​of the magnetic induction intensity in one magnetization cycle respectively.

[0106] The integral form of formula (9) is

[0107]

[0108] The normalization constant 2 / (ΔB·π 2 ) into formula (10) to obtain the equivalent frequency feq for

[0109]

[0110] Substituting formula (11) into formula (8) yields the generalized Steinmetz waveform coefficient formula (GWcSE) under non-sinusoidal excitation:

[0111]

[0112] P v is the core loss density, λ is the waveform factor, K(B m ) is the variable loss coefficient, B m is the maximum value of magnetic induction density.

[0113] Square wave excitation waveform and corresponding magnetic flux density waveform are as follows: Figure 2 The function expression of the square wave excitation voltage in one cycle is

[0114]

[0115] The expression of the rate of change of magnetic induction intensity within one cycle is:

[0116]

[0117] Substituting equation (14) into equation (11), the equivalent frequency under square wave excitation is:

[0118]

[0119] The triangular wave excitation waveform and the corresponding magnetic flux density waveform are as follows: Figure 3 As shown. The function expression of triangular wave excitation in one cycle is:

[0120]

[0121] Similarly, the equivalent frequency of the triangle wave excitation is

[0122]

[0123]

[0124] By calculating the ratio of the area enclosed by the magnetic induction intensity curve and the coordinate axis under square wave and triangle wave excitation to that under sinusoidal excitation, the waveform coefficient λ of the square wave and triangle wave can be obtained. squ , tri They are:

[0125]

[0126] Substituting equation (20) and equation (21) into equation (12), and substituting equation (13) and equation (17) into equation (4) and equation (6) respectively, we can get the GWcSE formula under non-sinusoidal excitation. The iron loss calculation formula under non-sinusoidal excitation is shown in Table 1.

[0127] Table 1

[0128]

[0129] The calculation requires the fitting values ​​of system parameters α, β and K as well as the frequency f and the maximum magnetic density B. m The measured value of

[0130] Verification example:

[0131] Analytical formula for calculating iron loss based on experimental measurement

[0132] In order to obtain the analytical expression of the above-mentioned Steinmetz empirical correction formula, a sinusoidal experiment was conducted on the annular nanocrystal core. The laboratory soft magnetic material AC magnetic property test system was used to test the core loss of the annular nanocrystal at different magnetic flux densities (0.1~1.1T) and different frequencies (5~20kHz) under sinusoidal excitation. The measured values ​​of the core loss of the annular nanocrystal under sinusoidal excitation were fitted, and the fitting parameters of the Steinmetz empirical formula were obtained in Table 2. Substituting these parameters into the formula in Table 1, the analytical calculation formulas of different correction formulas under square wave and rectangular wave excitation can be obtained.

[0133] Table 2

[0134]

[0135] Non-sinusoidal excitation core loss measurement and verification

[0136] Construction of experimental platform

[0137] This example builds a non-sinusoidal high-frequency magnetic ring dynamic magnetic characteristics test system as shown. Non-sinusoidal excitation signals such as square waves and triangle waves are generated by a DC source through a DSP-controlled inverter circuit. The silicon carbide full-bridge inverter circuit can output square waves and triangle waves with a frequency of tens to hundreds of kHz. The DC blocking capacitor in the circuit can eliminate the DC component of the excitation power supply, avoid magnetic bias, and maintain the straightness of the waveform. The test platform is as follows Figure 3 shown.

[0138] The waveform data of the primary current i1(t) and the secondary voltage u2(t) are collected by the voltage probe and the current probe, and the dynamic hysteresis loop of the magnetic ring is obtained by equations (22) and (23), and the core loss of the magnetic ring is obtained by equation (24).

[0139]

[0140] Where, N1 is the number of turns on the primary side; N2 is the number of turns on the secondary side; S is the cross-sectional area of ​​the core; l is the effective magnetic path length of the core.

[0141] Therefore, the core loss per unit volume can be obtained by integrating the area of ​​the BH loop and multiplying it by the frequency f:

[0142]

[0143] use Figure 4 The non-sinusoidal test system shown in the figure performs no-load experiments on nanocrystalline materials and measures their core losses. The DSP software program is used to control the inverter circuit to output square and triangular waves with a frequency range of 1 to 20 kHz and a magnetic flux density range of 0.1 to 1.1 T. At the same time, the computer can read the actual values ​​of the primary current and secondary voltage in real time to obtain experimental data.

[0144] Comparison of Steinmetz modified formula under non-sinusoidal excitation

[0145] Through the sinusoidal experiment, we can get the empirical formula parameters k, α, β, and then we can get the calculation formula of OSE and its correction formula. For the parameter D in GWcSE i By fitting the calculated value with the experimental value, its parameter value can be obtained. The loss measurement results of the ring nanocrystalline core under square wave and triangle wave excitation are compared with the loss prediction calculation results of the modified formula to verify the calculation accuracy of GWcSE.

[0146] The loss calculation comparison results of nanocrystalline core under square wave and triangle wave excitation are shown in the figure. Figure 5 and Figure 6 As shown, Figure 5 This is a comparison chart of nanocrystalline core under 5kHz square wave and different magnetic flux density. Figure 6 This is a comparison chart of nanocrystalline core under 5kHz triangle wave and different magnetic flux density. Figure 5It can be seen that the calculated values ​​of WcSE and IGSE at high magnetic flux density (above 0.7T) are relatively close to the experimental measured values, but the calculated values ​​at low magnetic flux density are very different from the measured values. At the same time, it can be found that the predicted calculated values ​​of square wave loss by WcSE and IGSE are very close, which also indirectly reflects that WcSE and IGSE no longer have good accuracy in predicting non-sinusoidal losses under high frequency conditions; and overall, the calculated values ​​of OSE are very different from the measured values, and the accuracy is lower than that of MSE and IGSE. Therefore, for the non-sinusoidal loss prediction formula with a frequency above 20kHz, OSE, IGSE and WcSE do not have good calculation accuracy. For GWcSE, the calculated value is very close to the measured value in the entire magnetic flux density range, which shows that when predicting non-sinusoidal losses, the effect of dB / dt on B cannot be ignored in order to cater to the form of the original Steinmetz empirical formula. m impact.

[0147] The loss comparison results under triangular wave excitation are as follows: Figure 6 As shown. Figure 6 It can be seen that with the increase of magnetic flux density, the calculation accuracy of core loss by OSE, IGSE and WcSE is decreasing. Unlike square wave, the calculated values ​​of WCSE and IGSE are no longer similar, and their trends develop in two different directions: the calculated value of core loss by WcSE under rectangular wave excitation is larger than the experimental value, and the increase continues to increase with the increase of magnetic flux density; while the calculated value of core loss by IGSE under rectangular wave excitation is smaller than the experimental value. The error between the calculated value and the measured value of GWcSE is very small, and its accuracy is better than the above three methods.

[0148] By comparing various non-sinusoidal modified empirical formulas, starting from the loss principle and considering the influence of dB / dt on the loss, an improved generalized WcSE formula for high-frequency non-sinusoidal core loss calculation model is derived.

[0149] In this example, a magnetic property test system for high-frequency non-sinusoidal excitation soft magnetic materials was built, and the calculated values ​​of several empirical formulas and the new calculation model were compared and analyzed with the experimental measurement results, verifying the accuracy and practicality of the GWcSE formula given in the technical solution of the present invention.

[0150] Embodiment 2

[0151] The purpose of this embodiment is to provide a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the program.

[0152] Embodiment 3

[0153] The purpose of this embodiment is to provide a computer-readable storage medium.

[0154] A computer-readable storage medium stores a computer program, which executes the steps of the above method when executed by a processor.

[0155] Embodiment 4

[0156] The purpose of this embodiment is to provide a transformer core loss calculation system considering variable loss coefficients, including:

[0157] The variable coefficient loss calculation formula establishment module is configured to: consider the influence of high-frequency skin effect and dynamic hysteresis loop on core loss, and establish the variable coefficient loss calculation formula;

[0158] The equivalent frequency expression calculation module is configured to: bring the normalization constant into the integral form of the average value of the magnetic induction intensity within one period, and obtain the equivalent frequency expression;

[0159] The transformer core loss calculation module is configured as follows: based on the equivalent frequency expression and the variable coefficient loss calculation formula, a generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation is obtained, and based on the formula, the core loss of the nanocrystalline high-frequency transformer is calculated.

[0160] Embodiment 5

[0161] The purpose of this embodiment is to provide a computer program product containing instructions, which, when running on a computer, enables the computer to execute the methods and functions involved in any of the above embodiments.

[0162] The steps involved in the apparatus of the above embodiment correspond to the method embodiment 1, and the specific implementation method can refer to the relevant description part of embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood to include any medium that can store, encode or carry an instruction set for execution by a processor and enable the processor to execute any method in the present invention.

[0163] Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0164] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for calculating transformer core loss considering variable loss coefficient, characterized in that: include: Considering the influence of high-frequency skin effect and dynamic hysteresis loop on core loss, a variable coefficient loss calculation formula is established; Substituting the normalization constant into the integral form of the average value of magnetic induction intensity in one cycle, the equivalent frequency expression can be obtained; The generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation is obtained based on the equivalent frequency expression and the variable coefficient loss calculation formula. The core loss of nanocrystalline high-frequency transformer is calculated based on this formula.

2. The transformer core loss calculation method considering variable loss coefficient as claimed in claim 1 is characterized in that: When calculating the variable coefficient loss, the loss coefficient K is changed along with the magnetic flux density B. m The relationship curve is represented as a polynomial function: Where: D i is the coefficient of the loss coefficient K raised to the power of i, and K is obtained by fitting the measured values, where i=0, 1, 2, 3, 4.

3. The transformer core loss calculation method considering variable loss coefficient as claimed in claim 1 is characterized in that: The generalized Steinmetz waveform factor formula under non-sinusoidal excitation is: Among them, Pv is the core loss density.

4. The transformer core loss calculation method considering variable loss coefficient as claimed in claim 1 is characterized in that: When the non-sinusoidal excitation is square wave excitation: Obtain the function expression of the square wave excitation voltage in one cycle and the expression of the rate of change of the magnetic induction intensity in one cycle; Substituting the expression of the rate of change of magnetic induction intensity within one cycle into the equivalent frequency expression, the equivalent frequency under square wave excitation can be obtained; By calculating the ratio of the area enclosed by the magnetic induction intensity curve and the coordinate axis under square wave excitation to that under sine excitation, the square wave waveform coefficient can be obtained; Substituting the square wave waveform coefficient into the generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation, the generalized Steinmetz waveform coefficient formula under square wave excitation is obtained.

5. The transformer core loss calculation method considering variable loss coefficient as claimed in claim 1 is characterized in that: The generalized Steinmetz waveform coefficient formula under square wave excitation is:

6. The transformer core loss calculation method considering variable loss coefficient as claimed in claim 1 is characterized in that: When the non-sinusoidal excitation is a triangular wave excitation: Obtain the function expression of the triangle wave excitation in one cycle; Then obtain the equivalent frequency of the triangle wave excitation at; By calculating the ratio of the area enclosed by the magnetic induction intensity curve and the coordinate axis under triangular wave excitation to that under sine excitation, the waveform coefficient of the triangular wave can be obtained; Substituting the waveform coefficient of the triangular wave into the generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation, the generalized Steinmetz waveform coefficient formula under triangular wave excitation is obtained; Preferably, the generalized Steinmetz waveform coefficient formula under triangular wave excitation is:

7. A transformer core loss calculation system considering variable loss coefficients, characterized in that: include: The variable coefficient loss calculation formula establishment module is configured to: consider the influence of high-frequency skin effect and dynamic hysteresis loop on core loss, and establish the variable coefficient loss calculation formula; The equivalent frequency expression calculation module is configured to: bring the normalized constant into the integral form of the average value of the magnetic induction intensity in one period, and obtain the equivalent frequency expression; The transformer core loss calculation module is configured as follows: based on the equivalent frequency expression and the variable coefficient loss calculation formula, a generalized Steinmetz waveform coefficient formula under non-sinusoidal excitation is obtained, and based on the formula, the core loss of the nanocrystalline high-frequency transformer is calculated.

8. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the method according to any one of claims 1 to 6 is implemented.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the method described in any one of claims 1 to 6 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method described in any one of claims 1 to 6 are performed.

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