WPT system coupling mechanism loss calculation method and system based on partition calculation

Abstract

The invention relates to the technical field of wireless power transfer (WPT), particularly discloses a WPT system coupling mechanism loss calculation method and system based on partition calculation, and aims at the characteristics of nonuniform magnetic field intensity distribution and nonuniform magnetic flux density distribution of a coil. Discretizing the magnetic field intensity distribution diagram of the continuous coil and the magnetic flux density modulus distribution diagram of the magnetic core to obtain different coil subareas and magnetic core subareas, and calculating the area proportion of each coil subarea and the volume proportion of each magnetic core subarea; each coil partition takes the magnetic field intensity peak value of the coil partition as the magnetic field intensity value participating in calculation, and each magnetic core partition takes the magnetic flux density peak value of the magnetic core partition as the magnetic flux density participating in calculation, so that on the basis of an existing loss calculation model, the loss of each partition is independently calculated, and finally summation is carried out to obtain the loss calculation model. The total loss of the coil and the magnetic core is obtained, and the total loss of the coupling mechanism is further obtained. Experiments verify the accuracy of the method.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transfer (WPT), and in particular to a method and system for calculating coupling mechanism loss of a WPT system based on partition calculation. Background Art

[0002] Wireless Power Transfer (WPT) technology refers to the technology that uses the comprehensive application of electrical engineering theory, power electronics technology, and control theory to achieve the transmission of electrical energy from the power grid or battery to the electrical equipment in a non-electrical contact manner using magnetic fields, electric fields, microwaves, etc. The two commonly used wireless power transmission methods are magnetic-coupled wireless power transfer (MC-WPT) and electric-field coupled wireless power transfer (EC-WPT). MC-WPT technology is widely used in electric vehicles, rail transit, rotating mechanisms, medical implants, consumer electronics and other fields due to its relatively mature overall technology, stable transmission performance, and large transmission power range.

[0003] In the field of wireless charging technology, magnetic induction coupling mechanism is the core of wireless energy transmission. The energy transfer efficiency involved in this technology is directly affected by the distribution of magnetic field strength within the coupling mechanism. Although the popularity of wireless charging devices is increasing, most existing research focuses on optimizing the overall efficiency, but often ignores the non-uniformity of magnetic field strength at different positions in the coupling mechanism and its specific impact on energy loss. Summary of the invention

[0004] The present invention provides a WPT system coupling mechanism loss calculation method and system based on partition calculation, which solves the technical problem that the existing coupling mechanism loss calculation method does not take into account the non-uniformity of magnetic field strength at different positions, resulting in a large deviation between the calculated loss and the actual loss.

[0005] In order to solve the above technical problems, the present invention provides a method for calculating the coupling mechanism loss of a WPT system based on partition calculation, including:

[0006] The skin loss of the energy transfer coil is calculated, and the proximity loss of the energy transfer coil is calculated based on the area partition. The loss of the magnetic core is calculated based on the volume partition. The loss of the magnetic shielding plate is calculated. The skin loss, proximity loss, loss of the magnetic core and loss of the magnetic shielding plate of the energy transfer coil are summed to obtain the total loss of the coupling mechanism of the WPT system.

[0007] Furthermore, the proximity loss of the energy transfer coil is calculated based on the area partition, which specifically includes the steps of:

[0008] Obtaining the magnetic field intensity distribution diagram of the energy transmission coil at the working frequency f and discretizing it to obtain a discrete magnetic field distribution diagram of the coil;

[0009] According to the coil discrete magnetic field distribution diagram, the area with the same magnetic field strength is divided into a partition to obtain a plurality of coil partitions;

[0010] Calculate the area ratio of each coil partition to the energy transmission coil;

[0011] Calculate the proximity loss of each coil partition based on the peak value and area ratio of the magnetic field intensity of each coil partition;

[0012] The proximity losses of all coil partitions are summed to obtain the proximity loss of the energy transfer coil.

[0013] Furthermore, the proximity loss of the mth coil partition is Where M represents the total number of coil partitions, N represents the number of Litz wire strands used in the energy transmission coil, the diameter of a single Litz wire strand is d, the total length of the Litz wire is l, and S m represents the proportionality of the mth coil partition, H e-sm represents the peak value of the magnetic field intensity of the mth coil partition, is the proximity loss coefficient of different coil shapes related to the system operating frequency f, R DC Indicates the DC loss resistance of a single Litz wire.

[0014] Furthermore, the loss of the magnetic core is calculated based on the volume partition, specifically:

[0015] Determine the relationship between the core loss and the magnetic flux density per unit volume at the operating frequency f;

[0016] Obtaining a magnetic flux density modulus distribution diagram of the magnetic core at an operating frequency f and discretizing it to obtain a discrete magnetic core magnetic flux density modulus distribution diagram;

[0017] According to the magnetic flux density modulus distribution diagram of the discrete magnetic core, the area with the same magnetic flux density is divided into a partition, and a plurality of magnetic core partitions are obtained;

[0018] Calculate the volume ratio of each core partition to the core;

[0019] Based on the peak value of the magnetic flux density and the volume ratio of each magnetic core partition, the loss of each magnetic core partition is calculated according to the relationship between the magnetic core loss and the magnetic flux density per unit volume at the operating frequency f;

[0020] The loss of the core is obtained by summing the adjacent losses of all core partitions.

[0021] Furthermore, the loss P of the kth core partition is vk =cf a B vk b YV k ,k∈[1,K],B vk represents the peak value of the flux density of the kth core partition, Y represents the total volume of the core, V k represents the volume ratio of the kth core partition, c, a, b are constants related to the core itself, and K represents the total number of core partitions.

[0022] Furthermore, the specific values ​​of c, a, and b are obtained by fitting the loss curve with respect to frequency, and the fitting process is:

[0023] Obtain the unit volume loss p at different magnetic flux densities B v The relationship with frequency f is as follows: v =cf a B b The format of fitting is used to obtain p v Expressions about f;

[0024] Get the unit volume loss p at different magnetic flux density B at frequency f v ;

[0025] According to p v The expression of frequency f and the unit volume loss p under different magnetic flux density B at frequency f v Fitting at frequency f, p v Expression about B;

[0026] According to p v The expression about B determines the specific values ​​of c, a, and b.

[0027] Furthermore, the eddy current loss of the aluminum plate Among them, μ Al is the magnetic permeability of aluminum, γ Al is the electrical conductivity of aluminum, H rms is the magnetic field strength on the surface of the aluminum plate.

[0028] The present invention also provides a WPT system coupling mechanism loss calculation system based on partition calculation, and applies the WPT system coupling mechanism loss calculation method based on partition calculation, which mainly includes: a coil loss calculation unit, a magnetic core loss calculation unit, a magnetic shielding plate loss calculation unit, and a coupling mechanism total loss calculation unit;

[0029] The coil loss calculation unit is used to calculate the skin loss of the energy transfer coil and the adjacent loss of the energy transfer coil based on area partitioning to obtain the total loss of the energy transfer coil;

[0030] The core loss calculation unit is used to calculate the loss of the core based on volume partitioning;

[0031] The magnetic shielding plate loss calculation unit is used for the loss of the magnetic shielding plate;

[0032] The coupling mechanism total loss calculation unit is used to sum the skin loss, proximity loss, core loss and magnetic shielding plate loss of the energy transfer coil to obtain the total loss of the coupling mechanism.

[0033] The WPT system coupling mechanism loss calculation method and system provided by the present invention based on partition calculation, in view of the characteristics of uneven distribution of coil magnetic field intensity and uneven distribution of magnetic flux density, discretizes the magnetic field intensity distribution diagram of the continuous coil and the magnetic flux density model distribution diagram of the magnetic core, obtains different coil partitions and magnetic core partitions, and calculates the area proportion of each coil partition and the volume proportion of the magnetic core partition, and each coil partition uses the peak value of the magnetic field intensity of the coil partition as the magnetic field intensity value involved in the calculation, and each core partition uses the peak value of the magnetic flux density of the core partition as the magnetic flux density involved in the calculation, so that on the basis of the existing loss calculation model, the loss of each partition is calculated separately, and finally summed up to obtain the total loss of the coil and the magnetic core, and the total loss of the magnetic shielding plate is calculated based on the existing loss model, and then all losses are added to obtain the total loss of the coupling mechanism. Finally, based on the actual wireless energy transmission system, the proposed partition loss calculation method is used to calculate the loss data of the coupling mechanism part, and compared with the loss of the actual system, the system efficiency calculated by the present invention is only 0.086% different from the measured efficiency, which verifies the accuracy of the present invention.

[0034] The present invention utilizes high-precision measurement and finite element simulation methods to quantitatively describe the distribution of magnetic field strength in each region and its impact on the overall transmission efficiency. This method of partitioning loss calculation not only helps to more accurately describe the loss generated by the coupling mechanism of the wireless charging system, but also can guide the targeted optimization of the coupling mechanism when designing a more efficient and safe wireless charging solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is an example diagram of a coil discrete magnetic field distribution diagram provided by an embodiment of the present invention;

[0036] Figure 2 is a graph showing the relationship between the LP-9 core loss and the frequency provided by an embodiment of the present invention;

[0037] Figure 3 is a magnetic field intensity diagram of the surface of an aluminum plate provided by an embodiment of the present invention;

[0038] Figure 4 is a schematic diagram of a coupling mechanism provided by an embodiment of the present invention;

[0039] Figure 5 is a magnetic field intensity distribution diagram of the primary and secondary coils provided in an embodiment of the present invention;

[0040] Figure 6 is a discrete magnetic field distribution diagram of a primary coil provided by an embodiment of the present invention;

[0041] Figure 7 is a discrete magnetic field distribution diagram of a secondary coil provided in an embodiment of the present invention;

[0042] Figure 8 is a magnetic flux density model distribution diagram of the primary and secondary magnetic cores provided by an embodiment of the present invention;

[0043] Fig. 9 is a distribution diagram of the magnetic flux density modulus of a discrete magnetic core of a primary magnetic core provided by an embodiment of the present invention;

[0044] Fig.10 is a distribution diagram of the magnetic flux density modulus of the discrete magnetic core of the secondary magnetic core provided by an embodiment of the present invention;

[0045] Fig.11 This is a diagram of actual system transmission conditions provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The following specifically illustrates the implementation mode of the present invention in conjunction with the accompanying drawings. The embodiments are provided for illustrative purposes only and cannot be understood as limiting the present invention. The accompanying drawings are provided for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0047] The loss of the coupling mechanism of the wireless power transmission system mainly includes three parts, namely coil loss, core loss and magnetic shielding plate loss (magnetic shielding plate is mostly made of aluminum plate). According to finite element simulation, the partition loss of each part is analyzed under normal working conditions. The WPT system coupling mechanism loss calculation method based on partition calculation provided by the embodiment of the present invention includes:

[0048] Calculate the skin loss of the energy transmission coil (transmitting coil, receiving coil, relay coil and other coils used for wireless energy transmission), calculate the proximity loss of the energy transmission coil based on area partitioning; calculate the loss of the magnetic core based on volume partitioning; calculate the loss of the magnetic shielding plate; sum the skin loss, proximity loss, magnetic core loss and magnetic shielding plate loss of the energy transmission coil to obtain the total loss of the coupling mechanism of the WPT system;

[0049] The proximity loss of the energy transfer coil is calculated based on area partitioning, which specifically includes the following steps:

[0050] Obtaining the magnetic field intensity distribution diagram of the energy transmission coil at the working frequency f and discretizing it to obtain a discrete magnetic field distribution diagram of the coil;

[0051] According to the coil discrete magnetic field distribution diagram, the area with the same magnetic field strength is divided into a partition to obtain a plurality of coil partitions;

[0052] Calculate the area ratio of each coil partition to the energy transmission coil;

[0053] Calculate the proximity loss of each coil partition based on the peak value and area ratio of the magnetic field intensity of each coil partition;

[0054] The proximity losses of all coil partitions are summed to obtain the proximity loss of the energy transfer coil.

[0055] The loss calculation of the magnetic core based on volume partitioning includes the following steps:

[0056] Determine the relationship between the core loss and the magnetic flux density per unit volume at the operating frequency f;

[0057] Obtaining a magnetic flux density modulus distribution diagram of the magnetic core at an operating frequency f and discretizing it to obtain a discrete magnetic core magnetic flux density modulus distribution diagram;

[0058] According to the magnetic flux density modulus distribution diagram of the discrete magnetic core, the area with the same magnetic flux density is divided into a partition, and a plurality of magnetic core partitions are obtained;

[0059] Calculate the volume ratio of each core partition to the core;

[0060] Based on the peak value of the magnetic flux density and the volume ratio of each magnetic core partition, the loss of each magnetic core partition is calculated according to the relationship between the magnetic core loss and the magnetic flux density per unit volume at the operating frequency f;

[0061] The loss of the core is obtained by summing the adjacent losses of all core partitions.

[0062] Coil loss mainly comes from high-frequency AC current, which is usually the main source of loss in the coupling mechanism. This loss is mainly divided into skin effect loss and proximity effect loss. In order to reduce the energy loss caused by skin effect, wireless power transmission systems often use multi-strand twisted Litz wire to optimize the coil design. This can more effectively disperse the current and reduce unnecessary losses.

[0063] Assume that the number of strands of the coil Litz wire is N, the diameter of a single strand of Litz wire is d, the total length of the Litz wire is l, d is much smaller than l, the resistivity of the copper wire is ρ, and the conductivity is γ. At this time, the DC loss resistance R of a single strand of Litz wire is DC The expression is:

[0064]

[0065] The skin depth δ of a single Litz line can be expressed as follows:

[0066]

[0067] Where μ0 is the magnetic permeability constant, μ r is the relative magnetic permeability of the copper conductor, μ r =1, f is the frequency of the sinusoidal current passing through the wire, that is, the operating frequency of the system.

[0068] Therefore, the expression of skin loss of N strands of Litz wire can be obtained as:

[0069]

[0070] Among them, I m Indicates the peak current of the energy transmission coil. is the skin loss coefficient of conductors of different shapes, which is used to describe the increase in impedance due to the skin effect. AC Represents AC impedance, R DC Indicates the DC loss resistance of a single strand of Litz wire. F R (f) is the coefficient of skin loss, and its expression is:

[0071]

[0072] Among them, the expression of ξ is:

[0073]

[0074] ber n (ξ) and bei n (ξ) is the nth order first kind Kelvin function with respect to ξ The real and imaginary parts of are expressed as:

[0075]

[0076] Among them, Re() means taking the real part, Im() means taking the imaginary part, e is the natural base, and j is the imaginary unit.

[0077] Calculate F R (f) = 0.5.

[0078] The expression of proximity loss of N Litz lines is:

[0079]

[0080] Among them, H e is the magnitude of the external magnetic field strength, is the proximity loss coefficient of different coil shapes related to the system operating frequency f, which is used to describe the coil loss caused by the proximity effect. Since the energy transmission coils in this example all use cylindrical Litz wire, the proximity loss coefficient G of the cylindrical Litz wire is R (f) is calculated by the following formula:

[0081]

[0082] It can be seen that the proximity loss of the coupling mechanism is proportional to the square of the magnetic field strength. At present, most studies analyze the proximity loss based on the average and peak values ​​of the magnetic field strength, which lacks certain accuracy. Therefore, the present invention calculates the partition loss of the coil part according to the magnetic field strength of the specific part. The specific process is as follows:

[0083] According to the finite element simulation, the magnetic field distribution diagram of the coil part is expressed in a discrete form in a two-dimensional plane, as shown in the following figure: Figure 1 The discrete magnetic field distribution diagram of the coil is shown.

[0084] Then according to Figure 1 The partition situation in the figure is obtained, and M coil partitions are obtained. The magnetic field intensity of each coil partition is selected as the peak value of the magnetic field intensity in the area. The magnetic field intensities of the M coil partitions are H e-s1 , H e-s2 To H e-sM ;

[0085] Calculate the area ratios of M coil partitions S1%, S2% to S M %, and obtain the corresponding proportions S1, S2 to S M .

[0086] Combining the formula shown in equation (7) and the magnetic field strength H of the M coil partitions e-s1 , H e-s2 To H e-sM and ratios S1, S2 to S M Calculate the proximity loss of M coil partitions using the following formula:

[0087]

[0088] represents the proximity loss of the mth coil partition.

[0089] The proximity loss expression of the entire coil is:

[0090]

[0091] Therefore, the total loss of a single coil is:

[0092] P loss-Cu =P skin+P proximity (11)

[0093] The core loss can be calculated by combining finite element simulation and Steinmetz formula. According to Steinmetz formula, the core loss per unit volume is:

[0094] P v =cf a B b (12)

[0095] P v is the core loss per unit volume, in kW / m 3 , f is the operating frequency, in kHz, and B is the amplitude corresponding to the effective magnetic flux density in the core, in T. Generally speaking, at a fixed frequency, c, f, a, and b in equation (12) are all constants. The specific values ​​of c, a, and b are related to the core itself and can be obtained by fitting the loss curve with respect to frequency provided in the core data sheet.

[0096] For the common LP-9 material core, the unit volume loss p at different magnetic flux densities (B = 50mT, 100mT, 150mT, 200mT, 300mT) v The relationship with frequency f is as follows Figure 2 As shown:

[0097] The fitting results show that p is 50mT, 100mT, 150mT, 200mT, and 300mT when B= v The expressions for f are:

[0098] p v-50mT =1.9961×f 2.1299 ×0.05 2.8392 (13)

[0099] p v-100mT =0.0529×f 2.0974 ×0.1 1.3378 (14)

[0100] p v-150mT =0.3131×f 1.7891 ×0.15 1.1241 (15)

[0101] p v-200mT =0.4147×f 1.5846 ×0.2 0.3753 (16)

[0102] p v-200mT =0.4147×f 1.5846 ×0.2 0.3753(17)

[0103] Read the values ​​at different B at 85kHz. When f=85kHz, the values ​​of these five groups of curves are:

[0104]

[0105] Using the above data fitting method, we can get p at 85kHz. v The expression for B is:

[0106] p v =cf a B b =1.5498×85 2.1452 ×B 2.7652 (19)

[0107] That is, we get c=1.5498, a=2.1452, c=2.7652.

[0108] According to the finite element simulation, the number of discrete frequency bands is selected to obtain the magnetic flux density modulus distribution area of ​​the corresponding frequency band under rated working conditions, including K core partitions. The magnetic flux density of each core partition takes the peak value of the magnetic flux density in the volume area. The magnetic flux density of K core partitions is B v1 To B vK .

[0109] The volume proportions of the K core partitions are: V1%, V2% to V K %, and the corresponding volume ratios are V1, V2 to V K Assume that the total volume of the core is Y(m 3 ), combined with the formula shown in formula (19), the calculation expression of each core partition loss is as follows:

[0110]

[0111] P vk =cf a B vk b YV k represents the loss of the kth core partition.

[0112] The total loss of the core is:

[0113]

[0114] Aluminum plates are widely used in electromagnetic shielding of electromagnetic coupling mechanisms. When they are covered on the back and around the coupling mechanism, the alternating magnetic field acts on the aluminum plate and generates eddy currents on the aluminum surface. The eddy current loss of the aluminum plate can be calculated according to the following formula:

[0115]

[0116] In the formula, μ Al is the magnetic permeability of aluminum, γ Al is the electrical conductivity of aluminum, H rms is the magnetic field strength on the surface of the aluminum plate.

[0117] Using COMSOL finite element simulation, impedance boundary conditions can be added to the surface of the aluminum plate, and the aluminum plate loss can be obtained by performing surface integration on the built-in surface loss density. Generally speaking, the value of aluminum plate loss is related to H rms However, in the actual wireless charging system, the magnetic field strength of most of the aluminum plates is not significantly different. It can be considered that the magnetic field strength of the aluminum plate is uniform and does not need to be divided into different areas. Figure 3 shown.

[0118] Finally, the total loss of the coupling mechanism is equal to the sum of the losses of all energy transfer coils, all magnetic cores, and all magnetic shielding plates.

[0119] Based on the above-mentioned WPT system coupling mechanism loss calculation method based on partition calculation, an embodiment of the present invention also provides a WPT system coupling mechanism loss calculation system based on partition calculation, which includes a coil loss calculation unit, a magnetic core loss calculation unit and a magnetic shielding plate loss calculation unit, and a coupling mechanism total loss calculation unit;

[0120] The coil loss calculation unit is used to calculate the skin loss of the energy transfer coil and the adjacent loss of the energy transfer coil based on area partitioning to obtain the total loss of the energy transfer coil;

[0121] The core loss calculation unit is used to calculate the loss of the core based on volume partitioning;

[0122] The magnetic shielding plate loss calculation unit is used for the loss of the magnetic shielding plate;

[0123] The coupling mechanism total loss calculation unit is used to sum the skin loss, proximity loss, core loss and magnetic shielding plate loss of the energy transfer coil to obtain the total loss of the coupling mechanism.

[0124] The specific loss calculation method is as described in the above calculation method and will not be repeated in the system.

[0125] The simulation model of the coupling mechanism is established in the finite element simulation software COMSOL. Figure 4 As shown, the coupling mechanism includes a primary aluminum plate, a primary magnetic core, a primary coil (transmitting coil), a secondary coil (receiving coil), a secondary magnetic core, and a secondary aluminum plate from the bottom layer to the top layer, and the parameters are shown in Table 1.

[0126] Table 1 Coupling mechanism parameters

[0127] Original Edge Secondary side Coil outer diameter (mm) 600 600 Coil inner diameter (mm) 330 330 Coil turns 9 9 Core outer diameter (mm) 700 700 Core inner diameter (mm) 100 100 Aluminum plate outer diameter (mm) 720 720

[0128] In this example, 30kW wireless power transmission is used as an example, and the currents of the transmitting coil and the receiving coil are:

[0129]

[0130] The magnetic field model of the coupling mechanism coil part is obtained by simulation. Figure 5 As shown, further discretization can obtain the discrete magnetic field distribution diagram of the primary coil as shown in Figure 6 As shown, the discrete magnetic field distribution diagram of the secondary coil is as follows Figure 7 As shown. Figure 6 , Figure 7 As shown in Figure 2, the magnetic field norm in the primary and secondary coils is divided into five regions (corresponding to five colors). The corresponding area ratios are calculated and shown in Table 2.

[0131] Table 2 Coil magnetic field mode area ratio

[0132]

[0133] The magnetic flux density of the coupling mechanism core obtained by simulation is as follows Figure 8 As shown, further discretization results in the magnetic flux density model distribution diagrams of the primary core and the secondary core as shown in Fig. 9 and Fig.10 According to the five colors, the magnetic field modes in the primary and secondary cores are divided into five regions, and the volume proportion of each region is shown in Table 3.

[0134] Table 3 Secondary core flux density partition ratio

[0135]

[0136] The number of strands of the Litz wire used is 2625 and the wire diameter is 5.1×10 -5 m, the total length of the coil is 18.48 m. Combining formula (3), formula (21) and the partition loss model of the coupling mechanism, the total losses of the primary coil and the secondary coil can be calculated as follows:

[0137]

[0138] The core is 700mm*700mm, the middle is hollowed out 100mm*100mm, and the core height is 10mm, so the core volume can be estimated to be 0.0048m 3 Combining formula (19), formula (21) and the core partition loss model, we can get the losses of the primary core and the secondary core respectively:

[0139]

[0140] By using COMSOL finite element simulation, impedance boundary conditions can be added to the surface of the aluminum plate. By performing surface integration on the built-in surface loss density, the losses of the original and secondary aluminum plates can be obtained:

[0141]

[0142] Therefore, the total loss of the coupling mechanism can be obtained as:

[0143]

[0144] In addition, the calculated resonant component and inverter losses are approximately 240.1W and 358.38W. Therefore, the total system loss P Loss =884W, at this time the total system input P in =31571W, it can be calculated that the system efficiency is about

[0145] η=1-P Loss / P in ×100%=97.2% (28)

[0146] The system efficiency is measured as Fig.11 As shown, the efficiency of the partition model differs from the measured efficiency (97.114%) by only 0.086%, which proves that the loss model has high accuracy and can provide a reference for loss estimation of wireless power transmission systems.

[0147] In summary, the WPT system coupling mechanism loss calculation method and system provided by the present invention based on partition calculation, in view of the characteristics of uneven distribution of coil magnetic field intensity and uneven distribution of magnetic flux density, discretizes the magnetic field intensity distribution diagram of the continuous coil and the magnetic flux density model distribution diagram of the magnetic core, obtains different coil partitions and magnetic core partitions, and calculates the area proportion of each coil partition and the volume proportion of the magnetic core partition, and each coil partition uses the peak value of the magnetic field intensity of the coil partition as the magnetic field intensity value involved in the calculation, and each core partition uses the peak value of the magnetic flux density of the core partition as the magnetic flux density involved in the calculation, so that on the basis of the existing loss calculation model, the loss of each partition is calculated separately, and finally summed up to obtain the total loss of the coil and the magnetic core, and the total loss of the magnetic shielding plate is calculated based on the existing loss model, and then all losses are added to obtain the total loss of the coupling mechanism. Finally, based on the actual wireless power transmission system, the proposed partition loss calculation method is used to calculate the loss data of the coupling mechanism part, and compared with the loss of the actual system, the system efficiency calculated by the present invention is only 0.086% different from the measured efficiency, which verifies the accuracy of the present invention.

[0148] The present invention utilizes high-precision measurement and finite element simulation methods to quantitatively describe the distribution of magnetic field strength in each region and its impact on the overall transmission efficiency. This method of partitioning loss calculation not only helps to more accurately describe the loss generated by the coupling mechanism of the wireless charging system, but also can guide the targeted optimization of the coupling mechanism when designing a more efficient and safe wireless charging solution.

[0149] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for calculating the coupling mechanism loss of a WPT system based on partition calculation, characterized in that: include: Calculate the skin loss of the energy transfer coil and calculate the proximity loss of the energy transfer coil based on area partitioning; Calculate the core losses based on volume partitioning; Calculate the losses of the magnetic shielding plate; The skin loss, proximity loss, core loss and magnetic shielding plate loss of the energy transfer coil are summed to obtain the total loss of the WPT system coupling mechanism.

2. The method for calculating the coupling mechanism loss of a WPT system based on partition calculation according to claim 1 is characterized in that: The proximity loss of the energy transfer coil is calculated based on area partitioning, which specifically includes the following steps: Obtaining a magnetic field intensity distribution diagram of the energy transmission coil at an operating frequency f and discretizing it to obtain a discrete magnetic field distribution diagram of the coil; According to the coil discrete magnetic field distribution diagram, the area with the same magnetic field strength is divided into a partition to obtain a plurality of coil partitions; Calculate the area ratio of each coil partition to the energy transmission coil; Calculate the proximity loss of each coil partition based on the peak value and area ratio of the magnetic field intensity of each coil partition; The proximity losses of all coil partitions are summed to obtain the proximity loss of the energy transfer coil.

3. The method for calculating the coupling mechanism loss of a WPT system based on partition calculation according to claim 2 is characterized in that: Proximity loss of the mth coil partition Where M represents the total number of coil partitions, N represents the number of Litz wire strands used in the energy transmission coil, the diameter of a single Litz wire strand is d, the total length of the Litz wire is l, and S m represents the proportionality of the mth coil partition, H e-sm represents the peak value of the magnetic field intensity of the mth coil partition, is the proximity loss coefficient of different coil shapes related to the system operating frequency f, R DC Indicates the DC loss resistance of a single Litz wire.

4. The method for calculating the coupling mechanism loss of a WPT system based on partition calculation according to claim 1 is characterized in that: The loss of the magnetic core is calculated based on volume partitioning, specifically: Determine the relationship between core loss and magnetic flux density per unit volume at operating frequency f; Obtaining a magnetic flux density modulus distribution diagram of the magnetic core at an operating frequency f and discretizing it to obtain a discrete magnetic core magnetic flux density modulus distribution diagram; According to the magnetic flux density modulus distribution diagram of the discrete magnetic core, the area with the same magnetic flux density is divided into a partition, and a plurality of magnetic core partitions are obtained; Calculate the volume ratio of each core partition to the core; Based on the peak value of the magnetic flux density and the volume ratio of each magnetic core partition, the loss of each magnetic core partition is calculated according to the relationship between the magnetic core loss and the magnetic flux density per unit volume at the operating frequency f; The loss of the core is obtained by summing the adjacent losses of all core partitions.

5. The method for calculating the coupling mechanism loss of a WPT system based on partition calculation according to claim 4 is characterized in that: The loss P of the kth core partition vk =cf a B vk b YV k ,k∈[1,K],B vk represents the peak value of the magnetic flux density of the kth core partition, Y represents the total volume of the core, V k represents the volume ratio of the kth core partition, c, a, b are constants related to the core itself, and K represents the total number of core partitions.

6. The method for calculating the coupling mechanism loss of a WPT system based on partition calculation according to claim 5 is characterized in that: The specific values ​​of c, a, and b are obtained by fitting the loss curve with respect to frequency. The fitting process is: Obtain the unit volume loss p at different magnetic flux densities B v The relationship with frequency f is as follows: v =cf a B b The format of fitting is used to obtain p v Expressions about f; Get the unit volume loss p at different magnetic flux density B at frequency f v ; According to p v The expression of frequency f and the unit volume loss p under different magnetic flux density B at frequency f v Fitting at frequency f, p v Expression about B; According to p v The expression about B determines the specific values ​​of c, a, and b.

7. The method for calculating the coupling mechanism loss of a WPT system based on partition calculation according to claim 1 is characterized in that: Eddy current loss of aluminum plate Among them, μ Al is the magnetic permeability of aluminum, γ Al is the electrical conductivity of aluminum, H rms is the magnetic field strength on the surface of the aluminum plate.

8. A WPT system coupling mechanism loss calculation system based on partition calculation, applying the WPT system coupling mechanism loss calculation method based on partition calculation according to any one of claims 1 to 7, characterized in that: It includes a coil loss calculation unit, a magnetic core loss calculation unit, a magnetic shielding plate loss calculation unit, and a coupling mechanism total loss calculation unit; The coil loss calculation unit is used to calculate the skin loss of the energy transfer coil and the adjacent loss of the energy transfer coil based on area partitioning to obtain the total loss of the energy transfer coil; The core loss calculation unit is used to calculate the loss of the core based on volume partitioning; The magnetic shielding plate loss calculation unit is used for the loss of the magnetic shielding plate; The coupling mechanism total loss calculation unit is used to sum the skin loss, proximity loss, core loss and magnetic shielding plate loss of the energy transfer coil to obtain the total loss of the coupling mechanism.

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