A parameter design method of a wireless charging system resistant to wide-range fluctuation of coupling coefficient

Abstract

The application discloses a parameter design method of a wireless charging system with wide-range fluctuation of coupling coefficients, and belongs to the technical field of wireless power transmission. o (k ps ) according to the system output power fluctuation ratio delta, and calculates the coupling change multiples beta1 and beta2 under the system working frequencies f1 and f2 and the actual coupling change multiple beta0; step three is to calculate the system working frequency f2 according to the system working frequency f1 and the coupling change multiple beta1; step four is to determine the coupling coefficients in the system power-coupling curve P o (k ps ) of the application; and step five is to complete the setting of parameters of each compensation element and to calculate the primary side detuning rates alpha1 and alpha2 under the system working frequencies f1 and f2. The application has great advantages in practical application, because the system power fluctuation is always within 5% of the set value in the range of nearly 250% fluctuation of the coupling coefficients without introducing any control unit or AC switch.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless power transmission, and particularly relates to a parameter design method of a wireless charging system resistant to wide-range fluctuations of a coupling coefficient. BACKGROUND

[0002] Inductive Power Transfer (IPT) technology uses alternating electromagnetic field as a medium to realize non-physical contact transmission of energy from a power supply to a load, and has the characteristics of safe power supply, flexibility, reliability, etc. At present, IPT technology has been applied in many fields such as electric vehicles, unmanned aerial vehicles, underwater exploration, etc. However, in most application scenarios, the transmitting coil and the receiving coil inevitably appear to be misaligned, the mutual inductance and the coupling parameters between the coils fluctuate dramatically, and thus the output power and the transmission efficiency of the IPT system are greatly affected.

[0003] In view of the above problems, domestic and foreign research teams have carried out research from three aspects of closed-loop control technology, compensation topology design and modal switching technology. Among them, the anti-offset technology using control is the most accurate in maintaining system output power; however, a DC-DC converter needs to be introduced additionally, or the phase-shifted control is performed on the inverter module, and when pulse frequency modulation is involved, the system frequency splitting phenomenon easily occurs, which greatly reduces the system stability; in addition, when the coupling coefficient fluctuation range is large, the system control is relatively complex due to the limited modulation margin. In order to reduce the control pressure and the system control complexity, some scholars have shifted their attention to compensation topology design; for example, a SS compensation topology with primary side detuning is proposed by Huazhong University of Science and Technology, and a design method of detuning rate and self-inductance value is given. The experiment shows that under the coupling coefficient fluctuation of nearly 200%, the output power fluctuation is less than 20%, but the system efficiency is only 76%, and the degree of freedom of the parameter design method is low, that is, the self-inductance values of the two coupling coils need to be equal, which has limitations and difficulties in actual application and design; in addition, a hybrid topology based on SS and DLCC is proposed by the University of Auckland in New Zealand, which is input parallel-output parallel type. Within the offset range of X / Y direction ± 150 mm and Z direction ± 20 mm, the system output power fluctuation is less than 10%; however, when the receiving coil deviates from the allowed working interval or is completely removed, the current flowing through the transmitting coil will increase exponentially, which will directly damage the system. Meanwhile, the magnetic structure is relatively complex and the system has a rise in cost, volume and weight due to the use of four coupling coils. Further, some scholars have proposed modal switching technology; for example, Zhejiang University realizes the switching between five different modes by adding seven AC switches and reasonably designing the connection mode of the compensation topology, and each mode corresponds to a coupling coefficient fluctuation range, so that the offset distance is about 2.5 times higher than that of the traditional SS compensation topology. However, too many AC switch elements and modal switching need to rely on precise control and detection technology. SUMMARY

[0004] The present application is a wireless charging system parameter design method for resisting wide-range fluctuation of coupling coefficient, which can maintain the system power fluctuation within 5% under the coupling coefficient fluctuation of nearly 250% without introducing any control unit or AC switch, thus having great advantages in practical application.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is:

[0006] The application discloses a parameter design method of a wireless charging system with wide-range fluctuation of an anti-coupling coefficient.

[0007] Step one: according to the main circuit architecture of the wireless charging system and actual working condition requirements, system technical indexes are set. D , preset output power P oset , battery equivalent load R o , system output power fluctuation ratio δ, system working frequency f1, primary side transmitting coil L p , secondary side receiving coil L s .

[0008] The main circuit architecture of the wireless charging system specifically comprises a high-frequency inverter circuit, a primary side compensation network, a secondary side compensation network and a rectification filter circuit.

[0009] The primary side compensation network is composed of a primary side series compensation capacitor C p and a primary side transmitting coil L p .

[0010] Two output ends of the high-frequency inverter circuit are connected with two input ends of the primary side compensation network respectively.

[0011] The secondary side compensation network is composed of a secondary side series compensation capacitor C s , a secondary side loop compensation capacitor C s1 , a secondary side loop compensation inductor L s1 and a secondary side receiving coil L s .

[0012] Two input ends of the rectification filter circuit are connected with two output ends of the secondary side compensation network respectively.

[0013] Step two: according to the system output power fluctuation ratio δ, coupling change multiples β1 and β2 under the system working frequencies f1 and f2 and actual coupling change multiple β0 are calculated respectively.

[0014] Step three: according to the system working frequency f1 and the coupling change multiple β1, the system working frequency f2 is calculated.

[0015] Step four: each coupling coefficient in the system power-coupling curve P o (k ps ) is determined. Specifically, the minimum working coupling coefficient k min , the extreme coupling coefficient k ex1 under the system working frequency f1, the critical coupling coefficient k cri at the frequency switching time, the extreme coupling coefficient k ex2 under the system working frequency f2 and the maximum working coupling coefficient k max .

[0016] Step five: complete the setting of each compensation element parameter and calculate the primary side detuning rate α1 and α2 under the system working frequency f1 and f2 respectively.

[0017] Further, the wireless charging system has two working frequencies f1 and f2, and corresponds to different coupling coefficient fluctuation ranges respectively.

[0018] Further, when the wireless charging system works at frequency f1 or f2:

[0019] The primary side series compensation capacitor C p , the primary side transmitting coil L p form a series detuning network; the secondary side series compensation capacitor C s , the secondary side loop compensation capacitor C s1 , the secondary side loop compensation inductor L s1 , the secondary side receiving coil L s form a series resonance network;

[0020] Specifically:

[0021]

[0022] In the formula: α is the primary side detuning rate; ω is the system working angular frequency, that is, ω = 2πf, f is the system working frequency, that is, f1 or f2; j is the imaginary unit.

[0023] Further, when the wireless charging system works at frequency f1 or f2:

[0024] The transmission efficiency η of the wireless charging system is not affected by the primary side detuning rate α, and its value is only related to the quality factors Q p , Q s of the primary side transmitting coil and the secondary side receiving coil and the coupling coefficient k ps , and the specific expression is:

[0025]

[0026] In the formula: ξ is the loss coefficient, that is, Q p , Q s are the quality factors of the primary side transmitting coil and the secondary side receiving coil, that is, ω is the system working angular frequency, that is, ω = 2πf, f is the system working frequency, that is, f1 or f2; L p is the self-inductance value of the primary side transmitting coil, L s is the self-inductance value of the secondary side receiving coil; R p is the parasitic resistance value of the primary side transmitting coil, R sR is the parasitic resistance value of the secondary receiving coil; R eq R is the equivalent AC resistance value before the rectifier filter circuit.

[0027] Further, the step one specifically includes:

[0028] The definition of the system output power fluctuation ratio δ is:

[0029]

[0030] Wherein, P omax and P omin are the maximum and minimum values of the power allowed to be transmitted by the frequency-switching-based wireless power transmission system, and they have the following relationship:

[0031]

[0032] In the formula: P oset is the preset output power.

[0033] Further, the step two specifically includes:

[0034] The definition of the coupling variation multiple β1 of the system at the working frequency f1 is:

[0035]

[0036] Wherein, k max is the maximum working coupling coefficient, k cri is the critical coupling coefficient during frequency switching, and the coupling variation multiple β1 of the system at the working frequency f1 can be calculated by the following formula:

[0037]

[0038] In the formula: δ1 is the system output power fluctuation ratio at the working frequency f1 of the system;

[0039] The definition of the coupling variation multiple β2 of the system at the working frequency f2 is:

[0040]

[0041] Wherein, k cri is the critical coupling coefficient during frequency switching, k min is the minimum working coupling coefficient, and the coupling variation multiple β2 of the system at the working frequency f2 can be calculated by the following formula:

[0042]

[0043] In the formula: δ2 is the system output power fluctuation ratio at the working frequency f2 of the system;

[0044] The definition of the actual coupling variation multiple β0 is:

[0045]

[0046] Wherein, k max is the maximum working coupling coefficient, k min is the minimum working coupling coefficient, and the actual coupling variation multiple β0 can be calculated by the following formula:

[0047] β0=β1β2

[0048] Wherein, β1 is the coupling variation multiple at the system working frequency f1, and β2 is the coupling variation multiple at the system working frequency f2.

[0049] Further, the step three specifically includes:

[0050] The calculation formula of the system working frequency f2 is:

[0051] f2=β1f1

[0052] Wherein, β1 is the coupling variation multiple at the system working frequency f1, and f1 is the set system working frequency.

[0053] Further, the step four specifically includes:

[0054] The system power-coupling curve P o (k ps ) is shown in the figure, wherein the system output power Po increases first and then decreases with the decrease of the coupling coefficient kps, and the specific expression is:

[0055]

[0056] Wherein: B=αL p ; α is the primary side detuning rate; ω is the system working angular frequency, i.e. ω=2πf, f is the system working frequency, i.e. f1 or f2; L p is the self-inductance value of the primary side transmitting coil, L s is the self-inductance value of the secondary side receiving coil; U D is the voltage value of the direct current voltage source, and R o is the resistance value of the battery load.

[0057] The calculation formula of the critical coupling coefficient kcri when the frequency is switched in the system power-coupling curve P o (k ps ) is:

[0058]

[0059] Wherein, ω1 is the angular frequency of the system operating frequency f1, ω2 is the angular frequency of the system operating frequency f2; β1 is the coupling variation multiple under the system operating frequency f1, β2 is the coupling variation multiple under the system operating frequency f2; L s L is the self-inductance of the secondary receiving coil; o R is the resistance value of the battery load, and is defined to have the following relationship with other coupling coefficients in the curve:

[0060]

[0061] Wherein: β1 is the coupling variation multiple under the system operating frequency f1, β2 is the coupling variation multiple under the system operating frequency f2; k min K is the minimum operating coupling coefficient, k ex1 K is the extreme coupling coefficient under the system operating frequency f1, k ex2 K is the extreme coupling coefficient under the system operating frequency f2, k max K is the maximum operating coupling coefficient.

[0062] Further, the step five specifically includes:

[0063] The calculation formula of the primary side series compensation capacitor C p In the primary side compensation network is:

[0064]

[0065] The value range of the secondary side series compensation capacitor C s In the secondary side compensation network is:

[0066]

[0067] The calculation formula of the secondary side loop compensation capacitor C s1 In the secondary side compensation network is:

[0068]

[0069] The calculation formula of the secondary side loop compensation inductance L s1 In the secondary side compensation network is:

[0070]

[0071] The calculation formula of the primary side detuning rate α1 under the system operating frequency f1 is:

[0072]

[0073] The calculation formula of the primary side detuning rate α2 under the system operating frequency f2 is:

[0074]

[0075] In the formula: ω1 is the operating angular frequency of the system operating frequency f1, ω2 is the operating angular frequency of the system operating frequency f2; β1 is the coupling change multiple under the system operating frequency f1, β2 is the coupling change multiple under the system operating frequency f2; L p L is the self-inductance value of the primary side transmitting coil, s L is the self-inductance value of the secondary side receiving coil; R o R is the resistance value of the battery load; k cri K is the critical coupling coefficient when the frequency is switched.

[0076] The beneficial effects of the present application are:

[0077] 1. The present application can change the primary side detuning rate of the primary side compensation network by switching the operating frequency of the system, and the secondary side compensation network always maintains the series resonance state, so that the two different coupling coefficient fluctuation ranges are connected end to end.

[0078] 2. Without introducing any control unit or AC switch, the system power fluctuation is always within the set 5% in the range of coupling coefficient fluctuation close to 250%, the system transmission efficiency is not affected by the primary side detuning rate, the inverter switch tube always maintains the zero voltage conduction state, and the risk of overcurrent of the transmitting coil can be avoided.

[0079] 3. The wireless charging system parameter design method provided by the present application can directly perform assignment calculation without the help of any additional cycle iteration or optimization algorithm, realizes the rapid determination of all system parameters, and simplifies the system parameter design steps. DETAILED DESCRIPTION

[0080] Figure 1 It is a step flow chart of the wireless charging system parameter design method against wide range fluctuation of coupling coefficient in the embodiment of the present application;

[0081] Figure 2 It is a main circuit architecture schematic diagram of the wireless charging system against wide range fluctuation of coupling coefficient in the embodiment of the present application;

[0082] Figure 3 It is a fundamental wave equivalent circuit diagram of the wireless charging system against wide range fluctuation of coupling coefficient in the embodiment of the present application;

[0083] Figure 4 It is a fundamental wave equivalent circuit diagram of the wireless charging system against wide range fluctuation of coupling coefficient in the embodiment of the present application considering the parasitic resistance;

[0084] Figure 5 It is a schematic diagram of the system power-coupling curve in the embodiment of the present application;

[0085] Figure 6 Theoretical calculation diagram of system power-coupling curve in the embodiment of the present application. DETAILED DESCRIPTION

[0086] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0087] As shown in Figure 1 , the embodiment provides a wireless charging system parameter design method capable of resisting wide-range fluctuations of coupling coefficient, comprising the following steps:

[0088] Step one: according to the main circuit architecture of the wireless charging system and actual working condition requirements, system technical indexes are set. Specifically, they include: DC input voltage U D , preset output power P oset , battery equivalent load R o , system output power fluctuation ratio δ, system working frequency f1, primary side transmitting coil L p , secondary side receiving coil L s .

[0089] As shown in Figure 2 , the main circuit architecture of the wireless charging system specifically comprises: a high-frequency inverter circuit, a primary side compensation network, a secondary side compensation network and a rectification filter circuit.

[0090] The primary side compensation network is composed of a primary side series compensation capacitor C p and a primary side transmitting coil L p .

[0091] The two output ends of the high-frequency inverter circuit are respectively connected to the two input ends of the primary side compensation network.

[0092] The secondary side compensation network is composed of a secondary side series compensation capacitor C s , a secondary side loop compensation capacitor C s1 , a secondary side loop compensation inductor L s1 and a secondary side receiving coil L s .

[0093] The two input ends of the rectification filter circuit are respectively connected to the two output ends of the secondary side compensation network.

[0094] Step two: according to the system output power fluctuation ratio δ, the coupling variation multiples β1 and β2 under the system working frequencies f1 and f2 and the actual coupling variation multiple β0 are respectively calculated.

[0095] Step three: according to the system operating frequency f1 and its coupling variation multiple β1, the system operating frequency f2 is calculated;

[0096] Step four: determine the system power-coupling curve P o (k ps ) of each coupling coefficient. Specifically, it includes: the minimum operating coupling coefficient k min , the extreme coupling coefficient k ex1 under the system operating frequency f1, the critical coupling coefficient k cri at the frequency switching, the extreme coupling coefficient k ex2 under the system operating frequency f2, and the maximum operating coupling coefficient k max ;

[0097] Step five: complete the setting of each compensation element parameter and calculate the primary side detuning rate α1 and α2 under the system operating frequency f1 and f2 respectively.

[0098] As shown in Figure 5 , the wireless charging system has two operating frequencies f1 and f2, and corresponds to different coupling coefficient fluctuation ranges.

[0099] As shown in Figure 3 , when the operating frequency of the wireless charging system is f1 or f2:

[0100] The primary side series compensation capacitor C p , the primary side transmitting coil L p in the primary side compensation network form a series detuning network; the secondary side series compensation capacitor C s , the secondary side loop compensation capacitor C s1 , the secondary side loop compensation inductor L s1 , and the secondary side receiving coil L s in the secondary side compensation network form a series resonance network;

[0101] Specifically:

[0102]

[0103] In the formula: α is the primary side detuning rate; ω is the system operating angular frequency, that is, ω=2πf, f is the system operating frequency, that is, f1 or f2; j is the imaginary unit.

[0104] As shown in Figure 4 , when the operating frequency of the wireless charging system is f1 or f2:

[0105] The transmission efficiency η of the wireless charging system is not affected by the primary side detuning rate α, and its value only relates to the quality factors Q p , Q s of the primary side transmitting coil and the secondary side receiving coil and the coupling coefficient k psCorrelation, the specific expression is:

[0106]

[0107] In the formula: ξ is the loss coefficient, that is Q p , Q s The quality factor of the primary side transmitting coil and the secondary side receiving coil, that is ω is the system operating angular frequency, that is ω = 2πf, f is the system operating frequency, that is f1 or f2; L p The self-inductance value of the primary side transmitting coil, L s The self-inductance value of the secondary side receiving coil; R p The parasitic resistance value of the primary side transmitting coil, R s The parasitic resistance value of the secondary side receiving coil; R eq The equivalent ac resistance value before the rectifier filter circuit.

[0108] The step one specifically includes:

[0109] The definition formula of the system output power fluctuation ratio δ is:

[0110]

[0111] Wherein, P omax And P omin The maximum and minimum values of the power allowed to be transmitted by the wireless power transmission system based on frequency switching, and they have the following relationship:

[0112]

[0113] In the formula: P oset Is the preset output power.

[0114] The step two specifically includes:

[0115] The definition formula of the coupling change multiple β1 of the system operating frequency f1 is:

[0116]

[0117] Wherein, k max The maximum operating coupling coefficient, k cri The critical coupling coefficient when frequency switching, and the coupling change multiple β1 of the system operating frequency f1 can be calculated by the following formula:

[0118]

[0119] In the formula: δ1 is the system output power fluctuation ratio of the system operating frequency f1;

[0120] The definition of the coupling variation multiple β2 at the system operating frequency f2 is:

[0121]

[0122] Wherein, k cri is the critical coupling coefficient at frequency switching, k min is the minimum operating coupling coefficient, and the coupling variation multiple β2 at the system operating frequency f2 can be calculated by the following formula:

[0123]

[0124] In the formula: δ2 is the system output power fluctuation ratio at the system operating frequency f2.

[0125] The definition of the actual coupling variation multiple β0 is:

[0126]

[0127] Wherein, k max is the maximum operating coupling coefficient, k min is the minimum operating coupling coefficient, and the actual coupling variation multiple β0 can be calculated by the following formula:

[0128] β0=β1β2 (10)

[0129] In the formula: β1 is the coupling variation multiple at the system operating frequency f1, and β2 is the coupling variation multiple at the system operating frequency f2.

[0130] In actual design, in order to maximize the anti-coupling coefficient fluctuation ability of the system, the numerical values of the system output power fluctuation ratio δ1 at the system operating frequency f1 and the system output power fluctuation ratio δ2 at the system operating frequency f2 are set to be equal, so according to the formula (11) and the formula (13), the numerical values of the coupling variation multiple β1 at the system operating frequency f1 and the coupling variation multiple β2 at the system operating frequency f2 are also equal.

[0131] The step three specifically includes:

[0132] The calculation formula of the system operating frequency f2 is:

[0133] f2=β1f1 (11)

[0134] In the formula: β1 is the coupling variation multiple at the system operating frequency f1; and f1 is the set system operating frequency.

[0135] The step four specifically includes:

[0136] As Figure 5The system power-coupling curve P o (k ps ) is shown, in which the system output power Po decreases with the coupling coefficient k ps , and its value first increases and then decreases, and the specific expression is:

[0137]

[0138] In the formula: B = aL p ; a is the primary side detuning rate; ω is the system operating angular frequency, i.e. ω = 2πf, f is the system operating frequency, i.e. f1 or f2; L p is the self-inductance value of the primary side transmitting coil, L s is the self-inductance value of the secondary side receiving coil; U D is the voltage value of the DC voltage source, R o is the resistance value of the battery load.

[0139] Among them, at the extreme coupling coefficient k ex , the output power P o reaches the extreme P ex , and the specific expression is:

[0140]

[0141] The expression of the current I p flowing through the primary side transmitting coil L p of the wireless power transmission system based on frequency switching is:

[0142]

[0143] Further, when M ps → 0, I p is equal to:

[0144]

[0145] As can be seen from formula (15), when the secondary side receiving coil deviates from the allowed operating interval or is completely removed, the current flowing through the primary side transmitting coil will not increase exponentially, avoiding the risk of overcurrent of the transmitting coil.

[0146] The expression of the input impedance Z in and the phase angle θ in of the wireless charging system is:

[0147]

[0148] As can be seen from formula (16), the system input impedance Z in is inductive, so it is expected to realize zero-voltage conduction of the inverter switch tube; in addition, the input impedance phase angle θin The range of variation can be represented as: β is the coupling change factor at the system operating frequency f1 or f2.

[0149] In equations (12) to (16): B=αL p α is the primary side detuning rate, i.e. 0 < α < 1; X Lp =ωL p , ω is the system's operating angular frequency, i.e., ω = 2πf, where f is the system's operating frequency, i.e., f1 or f2; L p The self-inductance of the primary-side transmitting coil, L s The self-inductance of the secondary receiving coil, C p U is the capacitance value of the primary-side series compensation capacitor; D The voltage value of the DC voltage source, U AB This is the output voltage value of the high-frequency inverter circuit, i.e. R o The resistance value of the battery load, R eq This is the equivalent AC resistance value before the rectifier and filter circuit, i.e. j is the imaginary unit.

[0150] The system power-coupling curve P o (k ps The formula for calculating the critical coupling coefficient kcri during frequency switching in () is:

[0151]

[0152] Where ω1 is the angular frequency of the system operating frequency f1, and ω2 is the angular frequency of the system operating frequency f2; β1 is the coupling change factor at the system operating frequency f1, and β2 is the coupling change factor at the system operating frequency f2; L s R is the self-inductance value of the secondary receiving coil. o The resistance value of the battery load is specified, and it is related to... Figure 5 The other coupling coefficients in the curves shown have the following relationships:

[0153]

[0154] In the formula: β1 is the coupling change factor at the system operating frequency f1, and β2 is the coupling change factor at the system operating frequency f2; k min For the minimum working coupling coefficient, k ex1 The extreme coupling coefficients at the system operating frequency f1, k ex2 The extreme coupling coefficients at the system operating frequency f2, k max This is the maximum working coupling coefficient.

[0155] The step five specifically includes:

[0156] The primary side series compensation capacitor C p in the primary side compensation network has a calculation formula as:

[0157]

[0158] The secondary side series compensation capacitor C s in the secondary side compensation network has a value range as:

[0159]

[0160] The secondary side loop compensation capacitor C s1 in the secondary side compensation network has a calculation formula as:

[0161]

[0162] The secondary side loop compensation inductor L s1 in the secondary side compensation network has a calculation formula as:

[0163]

[0164] The primary side detuning rate α1 at the system operating frequency f1 has a calculation formula as:

[0165]

[0166] The primary side detuning rate α2 at the system operating frequency f2 has a calculation formula as:

[0167]

[0168] In the formula, ω1 is the operating angular frequency of the system operating frequency f1, ω2 is the operating angular frequency of the system operating frequency f2; β1 is the coupling change multiple at the system operating frequency f1, β2 is the coupling change multiple at the system operating frequency f2; L p is the self-inductance value of the primary side transmitting coil, L s is the self-inductance value of the secondary side receiving coil; R o is the resistance value of the battery load; k cri is the critical coupling coefficient when the frequency is switched.

[0169] In order to verify the correctness and feasibility of the anti-coupling coefficient wide range fluctuation wireless charging system parameter design method, the detailed parameter design process is given below in combination with a design example:

[0170] Firstly, the system technical indexes are given, which are shown in Table 1:

[0171] Table 1 System technical indexes

[0172]

[0173] According to the system output power fluctuation ratio δ shown in Table 1, the coupling change multiples β1 and β2 at the system operating frequencies f1 and f2 and the actual coupling change multiple β0 are calculated respectively, specifically as follows:

[0174]

[0175] Then, according to the system operating frequency f1 and its coupling change multiple β1, the system operating frequency f2 is calculated as follows:

[0176] f2 = β1f1 = 133.96 kHz (26)

[0177] Next, the minimum operating coupling coefficient k o , the extreme coupling coefficient k ps at the system operating frequency f1, the critical coupling coefficient k min at the frequency switching, the extreme coupling coefficient k ex1 at the system operating frequency f2, and the maximum operating coupling coefficient k cri in the system power-coupling curve P ex2 (k max ) can be determined by equations (17) and (18), and are shown in Table 2 as follows:

[0178] Table 2 Coupling coefficients in system power-coupling curve

[0179]

[0180] Further, according to the resonance condition or relationship between the compensation elements, i.e. equation (1), the parameters of the compensation elements are set and the primary side detuning rates α1 and α2 at the system operating frequencies f1 and f2 are calculated respectively, and are shown in Table 3 as follows. The value range of the secondary side series compensation capacitor C s is 11.71 nF to 29.09 nF, and 20 nF is taken as an example here.

[0181] Table 3 Parameters of system compensation elements

[0182]

[0183] Finally, based on the expression (12) of the system power-coupling curve P o (k ps ), and with the help of Mathematica mathematical analysis software, the theoretical calculation diagram of the system power-coupling curve is obtained as shown in Figure 6 . Combined with Figure 5 and Figure 6It can be seen that, in order to meet the technical index requirement of the system output power fluctuation ratio δ being 5%, when the system operating frequency is f2, the coupling coefficient k ps can be changed between 0.1166 and 0.1837; when the system operating frequency is f1, the coupling coefficient k ps can be changed between 0.1837 and 0.2896, i.e. the two different coupling coefficient fluctuation ranges are connected in a loop.

[0184] In summary, when the system operating frequency f2 is changed from f1 to f2 at the coupling coefficient k ps equaling to 0.1837, the coupling coefficient k ps can be changed between 0.1166 and 0.2896, i.e. the coupling coefficient fluctuation is close to 250%, the system output power range is 452.38W-500W, and the output power fluctuation is always within the set 5%, thus the application has the ability of anti-coupling coefficient wide range fluctuation constant power output, and realizes the maintenance of close to constant power transmission in a wide coupling coefficient fluctuation range.

[0185] The above is only the preferred embodiment of the application, and does not limit the application in any form. Although the application has been disclosed as above with the preferred embodiment, it is not intended to limit the application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the technical solution of the application, and the equivalent embodiments with equivalent changes are obtained. Any simple modification, equivalent replacement and improvement of the above embodiments, which does not depart from the technical solution of the application, the technical essence of the application, and the spirit and principles of the application, are still within the protection scope of the technical solution of the application.

Claims

1. A parameter design method of a wireless charging system resistant to wide-range fluctuation of coupling coefficient, characterized in that, It comprises the following steps: Step one: according to the main circuit architecture of wireless charging system and actual working condition requirements, set the system technical index, technical index includes direct current input voltage U D , preset output power P oset , battery equivalent load R o , system output power fluctuation ratio δ, system working frequency f1, primary side transmitting coil L p , secondary side receiving coil L s ; Step two: according to the system output power fluctuation ratio δ, the coupling change multiple β1 and β2 under the system operating frequency f1 and f2 and the actual coupling change multiple β0 are calculated respectively; Step three: according to the system operating frequency f1 and its coupling change multiple β1, the system operating frequency f2 is calculated; Step four: determine the system power-coupling curve P o (k ps ) of each coupling coefficient, including the minimum operating coupling coefficient k min , the extreme coupling coefficient k ex1 at the system operating frequency f1, the critical coupling coefficient k cri at the frequency switching, the extreme coupling coefficient k ex2 at the system operating frequency f2, and the maximum operating coupling coefficient k max ; Step five: the parameters of each compensation element are set and the primary side mismatch rate α1 and α2 under the system operating frequency f1 and f2 are calculated respectively.

2. The parameter design method of a wireless charging system with a wide range of anti-coupling coefficient fluctuations according to claim 1, characterized in that, The main circuit architecture of the wireless charging system comprises a high-frequency inverter circuit, a primary side compensation network, a secondary side compensation network and a rectifier filter circuit. The primary side compensation network includes a primary side series compensation capacitor C p and a primary side transmitting coil L p ; The two output ends of the high-frequency inverter circuit are connected to the two input ends of the primary side compensation network one by one. The secondary side compensation network includes a secondary side series compensation capacitor C s , a secondary side loop compensation capacitor C s1 , a secondary side loop compensation inductor L s1 , and a secondary side receiving coil L s ; The two input ends of the rectifier filter circuit are connected to the two output ends of the secondary side compensation network one by one.

3. The parameter design method of a wireless charging system with a wide range of anti-coupling coefficient fluctuations according to claim 1, characterized in that, The wireless charging system has two operating frequencies f1 and f2, and corresponds to different coupling coefficient fluctuation ranges respectively.

4. The parameter design method of a wireless charging system with a wide range of anti-coupling coefficients according to claim 1 or 3, characterized in that, When the operating frequency of the wireless charging system is f1 or f2: The primary side series compensation capacitor C in the primary side compensation network p The primary side transmitting coil L p forms a series detuned network; The secondary side series compensation capacitor C in the secondary side compensation network s The secondary side loop compensation capacitor C s1 The secondary side loop compensation inductor L s1 The secondary side receiving coil L s forms a series resonant network; Specifically: In the formula: α is the primary side mismatch rate; ω is the system operating angular frequency, that is, ω=2πf, f is the system operating frequency, that is, f1 or f2; j is the imaginary unit.

5. The parameter design method of a wireless charging system with a wide range of anti-coupling coefficient according to claim 1 or 3, characterized in that, When the operating frequency of the wireless charging system is f1 or f2: The transmission efficiency η of the wireless charging system is not affected by the primary side detuning rate α, and the value is only related to the quality factor Q of the primary side transmitting coil and the secondary side receiving coil p 、 s and the coupling coefficient k ps , and the specific expression is: In the formula, ξ is the loss coefficient, i.e. Q p , Q s are the quality factors of the primary side transmitting coil and the secondary side receiving coil respectively, i.e. ω is the working angular frequency of the system, i.e. ω = 2πf, f is the working frequency of the system, i.e. f1 or f2; L p is the self-inductance of the primary side transmitting coil, L s is the self-inductance of the secondary side receiving coil; R p is the stray resistance of the primary side transmitting coil, R s is the stray resistance of the secondary side receiving coil; R eq is the equivalent AC resistance value before the rectification filter circuit.

6. The parameter design method of a wireless charging system with a wide range of anti-coupling coefficient fluctuations according to claim 1, characterized in that, The step one specifically comprises: The definition formula of the system output power fluctuation ratio δ is: Among them, P omax and P omin These define the maximum and minimum allowable power transmission values ​​for frequency-switching-based wireless power transmission systems, and specify the following relationship between them: In the formula, P oset is a preset output power.

7. The parameter design method of a wireless charging system with a wide range of anti-coupling coefficient fluctuations according to claim 1, characterized in that, The step two specifically comprises: The definition formula of the coupling change multiple β1 under the system operating frequency f1 is: where k max is the maximum operating coupling coefficient, k cri is the critical coupling coefficient at the frequency switch, and the coupling variation factor β1at the operating frequency f1is calculated by the following equation: In the formula: δ1 is the system output power fluctuation ratio under the system operating frequency f1; The definition formula of the coupling change multiple β2 under the system operating frequency f2 is: where k cri is the critical coupling coefficient at the frequency switching, k min is the minimum operating coupling coefficient, and the coupling variation factor β2at the system operating frequency f2is calculated from In the formula: δ2 is the system output power fluctuation ratio under the system operating frequency f2; The definition formula of the actual coupling change multiple β0 is: where k max is the maximum operating coupling coefficient, k min is the minimum operating coupling coefficient, and the actual coupling variation factor β0may be calculated from the following equation: β0＝β1β2 In the formula: β1 is the coupling change multiple under the system operating frequency f1, and β2 is the coupling change multiple under the system operating frequency f2. 8.The parameter design method of a wireless charging system with a wide range of anti-coupling coefficient fluctuations according to claim 1, wherein, The step three specifically comprises: The calculation formula of the system operating frequency f2 is: f2=β1f1 In the formula: β1 is the coupling change multiple under the system operating frequency f1; f1 is the set system operating frequency.

9. The parameter design method of a wireless charging system with a wide range of anti-coupling coefficient fluctuations according to claim 1, characterized in that, The step four specifically comprises: The system power-coupling curve P o (k ps ), wherein the system output power Po increases first and then decreases with the decrease of the coupling coefficient kps, and the specific expression is: In the formula: B = aL p ; a is the primary side detuning rate; ω is the system operating angular frequency, i.e. ω = 2πf, f is the system operating frequency, i.e. f1 or f2; L p is the self-inductance value of the primary side transmitting coil, L s is the self-inductance value of the secondary side receiving coil; U D is the voltage value of the direct current voltage source, R o is the resistance value of the battery load; The system power-coupling curve P o (k ps The formula for calculating the critical coupling coefficient kcri at the frequency switching is: Wherein, ω1 is the angular frequency of the system operating frequency f1, ω2 is the angular frequency of the system operating frequency f2; β1 is the coupling change multiple under the system operating frequency f1, β2 is the coupling change multiple under the system operating frequency f2; L s L is the self-inductance of the secondary receiving coil; R o R is the resistance value of the battery load, and it is defined to have the following relationship with other coupling coefficients in the curve: wherein: β1 is the coupling variation factor at the system operating frequency f1, β2 is the coupling variation factor at the system operating frequency f2; k min is the minimum operating coupling factor, k ex1 is the minimum operating coupling factor, k ex2 is the minimum operating coupling factor, k max is the maximum operating coupling factor.

10. The parameter design method of a wireless charging system with a wide range of anti-coupling coefficient fluctuations according to claim 1, characterized in that, The step five specifically comprises: The primary side series compensation capacitor C in the primary side compensation network p The calculation formula is: The secondary side series compensation capacitor C in the secondary side compensation network s The value range of the secondary side series compensation capacitor C in the secondary side compensation network The secondary side loop compensation capacitor C in the secondary side compensation network s1 The calculation formula is: The secondary side loop compensation inductance L in the secondary side compensation network s1 The calculation formula is: The calculation formula of the primary side mismatch rate α1 under the system operating frequency f1 is: The calculation formula of the primary side mismatch rate α2 under the system operating frequency f2 is: In the formula, ω1 is the operating angular frequency of the system operating frequency f1, ω2 is the operating angular frequency of the system operating frequency f2; β1 is the coupling variation multiple under the system operating frequency f1, β2 is the coupling variation multiple under the system operating frequency f2; L p L is the self-inductance value of the primary side transmitting coil, s L is the self-inductance value of the secondary side receiving coil; R o R is the resistance value of the battery load; k cri k is the critical coupling coefficient when the frequency is switched.

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