Wireless charging system parameter design method capable of resisting wide-range fluctuation of coupling coefficient

Abstract

The invention discloses a wireless charging system parameter design method for resisting wide-range fluctuation of a coupling coefficient, and the method comprises the steps: 1, setting system technical indexes according to the main circuit architecture and actual working condition requirements of a wireless charging system; 2, according to the system output power fluctuation ratio delta, respectively calculating coupling change multiples beta1 and beta2 under the system working frequencies f1 and f2 and an actual coupling change multiple beta0; 3, calculating the system working frequency f2 according to the system working frequency f1 and the coupling change multiple beta1 thereof; step 4, determining each coupling coefficient in the system power-coupling curve Po (kps); and step 5, finishing setting of parameters of each compensation element and respectively calculating primary side detuning rates alpha 1 and alpha 2 under the working frequencies f1 and f2 of the system. On the premise of not introducing any control unit or alternating current switch, the power fluctuation of the system is always within the set 5% within the range that the fluctuation of the coupling coefficient is close to 250%, so that the method has great advantages in practical application. The invention belongs to the technical field of wireless power transmission.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transmission, and in particular to a method for designing parameters of a wireless charging system that is resistant to wide-range fluctuations in coupling coefficients. Background Art

[0002] Inductive Power Transfer (IPT) technology uses alternating electromagnetic fields as a medium to achieve non-physical contact transmission of energy from power source to load. It has the characteristics of safe, flexible and reliable power supply. It has been put into practical use in many fields such as electric vehicles, drones, and underwater detection. However, in most applications, the transmitting coil and the receiving coil are inevitably offset and misaligned, and the mutual inductance and coupling parameters between the coils fluctuate violently, which in turn has a significant impact on the output power and transmission efficiency of the IPT system.

[0003] In response to the above problems, domestic and foreign research teams have conducted research from three aspects: closed-loop control technology, compensation topology design, and mode switching technology. Among them, the anti-offset technology using control is the most accurate in maintaining the system output power; however, it is necessary to introduce an additional DC-DC converter, or perform phase shift control on the inverter module, and when pulse frequency modulation is involved, the system frequency splitting phenomenon is prone to occur, which greatly reduces the system stability; in addition, when the coupling coefficient fluctuates in a large range, the system control is relatively complex due to the limitation of the modulation margin. In order to reduce the control pressure and the complexity of system control, some scholars have turned their attention to the design of compensation topology. For example, Huazhong University of Science and Technology proposed an SS compensation topology with a primary-side detuning design, and gave a design method for the detuning rate and self-inductance parameters. Experiments showed that under a coupling coefficient fluctuation of nearly 200%, the output power fluctuation was less than 20%, but the system efficiency was only 76%, and the degree of freedom of the proposed parameter design method was low, requiring the self-inductance values ​​of the two coupling coils to be equal, which was limited and difficult in practical application and design. In addition, the University of Auckland in New Zealand proposed an input parallel-output parallel hybrid topology based on SS and DLCC. Within the offset range of ±150mm in the X / Y direction and ±20mm in the Z direction, the system output power fluctuation was less than 10%. However, when the receiving coil deviated from the allowed working range or was completely evacuated, the current flowing through the transmitting coil would surge exponentially, which would directly damage the system. At the same time, it used 4 coupling coils, the magnetic structure was relatively complex, and it brought an increase in cost, volume, and weight to the system. Furthermore, some scholars have proposed mode switching technology; for example, Zhejiang University has realized the switching between five different modes by adding 7 AC switches and rationally designing the connection mode of the compensation topology. Each mode corresponds to a coupling coefficient fluctuation range, and the offset distance is increased by about 2.5 times compared with the traditional SS compensation topology. However, too many AC switch components and mode switching require precise control and detection technology. Therefore, in the face of wide coupling coefficient fluctuations, how to maintain near-constant power transmission while reducing the complexity of system control and reducing the introduction of additional components is one of the key issues in IPT technology research. Summary of the invention

[0004] In order to solve the technical problems existing in the above-mentioned prior art, the present invention further proposes a wireless charging system parameter design method that is resistant to wide-range fluctuations in coupling coefficient. Without introducing any control unit or AC switch, the present invention can keep the system power fluctuation within the set range of 5% when the coupling coefficient fluctuates close to 250%, so it has great advantages in practical applications.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is:

[0006] The method for designing parameters of a wireless charging system that is resistant to wide-range fluctuations in coupling coefficients according to the present invention comprises the following steps:

[0007] Step 1: According to the main circuit architecture of the wireless charging system and the actual working conditions, set the system technical indicators. Specifically including: DC input voltage U D , preset output power P oset , Battery equivalent load R o , system output power fluctuation ratio δ, system operating frequency f1, primary transmitting coil L p , secondary receiving coil L s ;

[0008] The main circuit architecture of the wireless charging system specifically includes: a high-frequency inverter circuit, a primary compensation network, a secondary compensation network, and a rectifier and filter circuit;

[0009] The primary compensation network consists of a primary series compensation capacitor C p , primary transmitting coil L p constitute;

[0010] The two output ends of the high-frequency inverter circuit are respectively connected to the two input ends of the primary compensation network;

[0011] The secondary side compensation network consists of a secondary side series compensation capacitor C s , secondary loop compensation capacitor C s1 , secondary loop compensation inductor L s1 , secondary receiving coil L s constitute;

[0012] The two input ends of the rectifying and filtering circuit are respectively connected to the two output ends of the secondary side compensation network.

[0013] Step 2: According to the system output power fluctuation ratio δ, the coupling variation multiples β1 and β2 at the system operating frequencies f1 and f2 and the actual coupling variation multiple β0 are calculated respectively;

[0014] Step 3: Calculate the system operating frequency f2 based on the system operating frequency f1 and its coupling change multiple β1;

[0015] Step 4: Determine the system power-coupling curve P o (k ps ) in each coupling coefficient. Specifically including: minimum working coupling coefficient k min , the extreme coupling coefficient k at the system operating frequency f1 ex1 , critical coupling coefficient k during frequency switching cri 、The extreme coupling coefficient k at the system operating frequency f2 ex2 , maximum working coupling coefficient k max ;

[0016] Step 5: Complete the adjustment of the parameters of each compensation component and calculate the primary side detuning rates α1 and α2 at the system operating frequencies f1 and f2 respectively.

[0017] Furthermore, the wireless charging system has two operating frequencies f1 and f2, which correspond to different coupling coefficient fluctuation ranges respectively.

[0018] Furthermore, when the operating frequency of the wireless charging system is f1 or f2:

[0019] The primary side series compensation capacitor C in the primary side compensation network p , primary transmitting coil L p The secondary side series compensation capacitor C in the secondary side compensation network constitutes a series detuned network; s , secondary loop compensation capacitor C s1 , secondary loop compensation inductor L s1 , secondary receiving coil L s Form a series resonant network;

[0020] Specifically:

[0021]

[0022] Where: 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.

[0023] Furthermore, when the operating frequency of the wireless charging system is 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 factor Q of the primary side transmitting coil and the secondary side receiving coil. p , Q s And the coupling coefficient k ps Related, the specific expression is:

[0025]

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

[0027] Furthermore, the step 1 specifically includes:

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

[0029]

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

[0031]

[0032] Where: P oset The preset output power.

[0033] Furthermore, the step 2 specifically includes:

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

[0035]

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

[0037]

[0038] Where: δ1 is the system output power fluctuation ratio at the system operating frequency f1;

[0039] The definition of the coupling change factor β2 at the system operating frequency f2 is:

[0040]

[0041] Among them, k cri is the critical coupling coefficient during frequency switching, k min is the minimum working coupling coefficient, and the coupling change multiple β2 under the system working frequency f2 can be calculated by the following formula:

[0042]

[0043] Where: δ2 is the system output power fluctuation ratio at the system operating frequency f2;

[0044] The actual coupling variation factor β0 is defined as:

[0045]

[0046] Among them, k max is the maximum working coupling coefficient, k min is the minimum working coupling coefficient, and the actual coupling change multiple β0 is specified to be calculated by the following formula:

[0047] β0=β1β2

[0048] Where: β1 is the coupling change multiple at the system operating frequency f1, and β2 is the coupling change multiple at the system operating frequency f2.

[0049] Furthermore, the step three specifically includes:

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

[0051] f2=β1f1

[0052] Where: β1 is the coupling change multiple at the system operating frequency f1; f1 is the set system operating frequency.

[0053] Furthermore, the step 4 specifically includes:

[0054] The system power-coupling curve P o (k ps ), where the system output power Po increases first and then decreases as the coupling coefficient kps decreases. The specific expression is:

[0055]

[0056] Where: B=αL p ; 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; L p is the self-inductance of the primary transmitting coil, L s is the self-inductance of the secondary receiving coil; U D is the voltage value of the DC voltage source, R o is the resistance value of the battery load.

[0057] The system power-coupling curve P o (k ps ) The calculation formula of the critical coupling coefficient kcri during frequency switching 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 change multiple under the system operating frequency f1, β2 is the coupling change multiple under the system operating frequency f2; L s is the self-inductance of the secondary receiving coil; R o is the resistance value of the battery load, and it is stipulated that it has the following relationship with other coupling coefficients in the curve:

[0060]

[0061] Where: β1 is the coupling change multiple at the system operating frequency f1, β2 is the coupling change multiple at the system operating frequency f2; k min is the minimum working coupling coefficient, k ex1 is the extreme coupling coefficient at the system operating frequency f1, k ex2 is the extreme coupling coefficient at the system operating frequency f2, k max is the maximum working coupling coefficient.

[0062] Furthermore, the step five specifically includes:

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

[0064]

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

[0066]

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

[0068]

[0069] The secondary loop compensation inductor L in the secondary compensation network s1 The calculation formula is:

[0070]

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

[0072]

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

[0074]

[0075] Where: ω1 is the working angular frequency of the system operating frequency f1, ω2 is the working 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 is the self-inductance of the primary transmitting coil, L s is the self-inductance of the secondary receiving coil; R o is the resistance value of the battery load; k cri is the critical coupling coefficient during frequency switching.

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

[0077] 1. The present invention can change the primary-side detuning rate of the primary-side compensation network by switching the operating frequency of the system, while the secondary-side compensation network always maintains a series resonance state, thereby connecting two different coupling coefficient fluctuation ranges end to end.

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

[0079] 3. The wireless charging system parameter design method for resisting wide-range fluctuation of coupling coefficient provided by the present invention does not require any additional loop iteration or optimization algorithm, and can directly perform assignment calculation, thereby realizing rapid determination of all system parameters and simplifying the system parameter design steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 A flowchart of the steps of a method for designing parameters of a wireless charging system that is resistant to wide-range fluctuations in coupling coefficients in an embodiment of the present invention;

[0081] Figure 2 Schematic diagram of the main circuit architecture of a wireless charging system that is resistant to wide-range fluctuations in coupling coefficients according to an embodiment of the present invention;

[0082] Figure 3 It is a fundamental wave equivalent circuit diagram of a wireless charging system that is resistant to wide range fluctuation of coupling coefficient in an embodiment of the present invention;

[0083] Figure 4 A fundamental wave equivalent circuit diagram of a wireless charging system that is resistant to wide-range fluctuations in coupling coefficient in an embodiment of the present invention taking into account parasitic resistance;

[0084] Figure 5 Schematic diagram of a system power-coupling curve in an embodiment of the present invention;

[0085] Figure 6 It is a theoretical calculation diagram of the system power-coupling curve in an embodiment of the present invention. DETAILED DESCRIPTION

[0086] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0087] like Figure 1 As shown, this embodiment provides a method for designing parameters of a wireless charging system that is resistant to wide-range fluctuations in coupling coefficients, comprising the following steps:

[0088] Step 1: According to the main circuit architecture of the wireless charging system and the actual working conditions, set the system technical indicators. Specifically including: DC input voltage U D , preset output power P oset , Battery equivalent load R o , system output power fluctuation ratio δ, system operating frequency f1, primary transmitting coil L p , secondary receiving coil L s ;

[0089] like Figure 2 As shown, the main circuit architecture of the wireless charging system specifically includes: a high-frequency inverter circuit, a primary compensation network, a secondary compensation network, and a rectifier and filter circuit;

[0090] The primary compensation network consists of a primary series compensation capacitor C p , primary transmitting coil L p constitute;

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

[0092] The secondary side compensation network consists of a secondary side series compensation capacitor C s , secondary loop compensation capacitor C s1 , secondary loop compensation inductor L s1 , secondary receiving coil L s constitute;

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

[0094] Step 2: According to the system output power fluctuation ratio δ, the coupling variation multiples β1 and β2 at the system operating frequencies f1 and f2 and the actual coupling variation multiple β0 are calculated respectively;

[0095] Step 3: Calculate the system operating frequency f2 based on the system operating frequency f1 and its coupling change multiple β1;

[0096] Step 4: Determine the system power-coupling curve P o (k ps ) in each coupling coefficient. Specifically including: minimum working coupling coefficient k min , the extreme coupling coefficient k at the system operating frequency f1 ex1 , critical coupling coefficient k during frequency switching cri 、The extreme coupling coefficient k at the system operating frequency f2 ex2 , maximum working coupling coefficient k max ;

[0097] Step 5: Complete the adjustment of the parameters of each compensation component and calculate the primary side detuning rates α1 and α2 at the system operating frequencies f1 and f2 respectively.

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

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

[0100] The primary side series compensation capacitor C in the primary side compensation network p , primary transmitting coil L p The secondary side series compensation capacitor C in the secondary side compensation network constitutes a series detuned network; s , secondary loop compensation capacitor C s1 , secondary loop compensation inductor L s1 , secondary receiving coil L s Form a series resonant network;

[0101] Specifically:

[0102]

[0103] Where: 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] like Figure 4 As shown, 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 is only related to the quality factor Q of the primary side transmitting coil and the secondary side receiving coil. p , Q s And the coupling coefficient k psRelated, the specific expression is:

[0106]

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

[0108] The step 1 specifically includes:

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

[0110]

[0111] Among them, P omax and P omin are the maximum and minimum power values ​​allowed to be transmitted by the frequency switching-based wireless power transmission system, respectively, and they are stipulated to have the following relationship:

[0112]

[0113] Where: P oset The preset output power.

[0114] The step 2 specifically includes:

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

[0116]

[0117] Among them, k max is the maximum working coupling coefficient, k cri is the critical coupling coefficient during frequency switching, and the coupling change multiple β1 at the system operating frequency f1 can be calculated by the following formula:

[0118]

[0119] Where: δ1 is the system output power fluctuation ratio at the system operating frequency f1;

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

[0121]

[0122] Among them, k cri is the critical coupling coefficient during frequency switching, k min is the minimum working coupling coefficient, and the coupling change multiple β2 under the system working frequency f2 can be calculated by the following formula:

[0123]

[0124] Where: δ2 is the system output power fluctuation ratio at the system operating frequency f2;

[0125] The actual coupling variation factor β0 is defined as:

[0126]

[0127] Among them, k max is the maximum working coupling coefficient, k min is the minimum working coupling coefficient, and the actual coupling change multiple β0 is specified to be calculated by the following formula:

[0128] β0=β1β2 (10)

[0129] Where: β1 is the coupling change multiple at the system operating frequency f1, and β2 is the coupling change multiple at the system operating frequency f2.

[0130] In the actual design, in order to maximize the system's ability to resist coupling coefficient fluctuations, the 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. Therefore, according to equations (11) and (13), it can be seen that the values ​​of the coupling change multiple β1 at the system operating frequency f1 and the coupling change 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] Where: β1 is the coupling change multiple at the system operating frequency f1; f1 is the set system operating frequency.

[0135] The step 4 specifically includes:

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

[0137]

[0138] Where: B=αL p ; 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; L p is the self-inductance of the primary transmitting coil, L s is the self-inductance of the secondary 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 At, the output power P o Reaching the extreme value P ex , the specific expression is:

[0140]

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

[0142]

[0143] Furthermore, when M ps →0, I p equal:

[0144]

[0145] It can be seen from formula (15) that when the secondary receiving coil deviates from the allowed working range or is completely evacuated, the current flowing through the primary transmitting coil will not increase exponentially, thus avoiding the risk of overcurrent in the transmitting coil.

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

[0147]

[0148] From formula (16), we can see that the system input impedance Z in Inductive, it is expected to achieve zero voltage conduction of the inverter switch tube; in addition, the input impedance phase angle θin The variation range of can be expressed as: β is the coupling change multiple at the system operating frequency f1 or f2.

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

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

[0151]

[0152] 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 is the self-inductance of the secondary receiving coil; R o is the resistance value of the battery load and specifies it with Figure 5 The other coupling coefficients in the curves shown have the following relationships:

[0153]

[0154] Where: β1 is the coupling change multiple at the system operating frequency f1, β2 is the coupling change multiple at the system operating frequency f2; k min is the minimum working coupling coefficient, k ex1 is the extreme coupling coefficient at the system operating frequency f1, k ex2 is the extreme coupling coefficient at the system operating frequency f2, k max is the maximum working coupling coefficient.

[0155] The step five specifically includes:

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

[0157]

[0158] The secondary side series compensation capacitor C in the secondary side compensation network s The value range of is:

[0159]

[0160] The secondary loop compensation capacitor C in the secondary compensation network s1 The calculation formula is:

[0161]

[0162] The secondary loop compensation inductor L in the secondary compensation network s1 The calculation formula is:

[0163]

[0164] The calculation formula of the primary side detuning rate α1 at the system operating frequency f1 is:

[0165]

[0166] The calculation formula of the primary side detuning rate α2 at the system operating frequency f2 is:

[0167]

[0168] Where: ω1 is the working angular frequency of the system operating frequency f1, ω2 is the working 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 is the self-inductance of the primary transmitting coil, L s is the self-inductance of the secondary receiving coil; R o is the resistance value of the battery load; k cri is the critical coupling coefficient during frequency switching.

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

[0170] First, the system technical indicators are given, as shown in Table 1:

[0171] Table 1 System technical indicators

[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:

[0174]

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

[0176] f2=β1f1=133.96kHz (26)

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

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

[0179]

[0180] Further, according to the resonance condition or relationship between the compensation components, that is, formula (1), the parameters of the compensation components are adjusted and the primary side detuning rates α1 and α2 at the system operating frequencies f1 and f2 are calculated respectively, as shown in Table 3. s The value range is 11.71nF~29.09nF, here we take 20nF as an example.

[0181] Table 3 Parameters of compensation components in the system

[0182]

[0183] Finally, based on the system power-coupling curve P o (k ps ) expression (12), and with the help of Mathematica mathematical analysis software, we get Figure 6 The theoretical calculation diagram of the system power-coupling curve is shown in Figure 2. Figure 5 and Figure 6It can be seen that in order to meet the technical indicator requirement of the system output power fluctuation ratio δ of 5%, when the system operating frequency is f2, the coupling coefficient k ps It can vary between 0.1166 and 0.1837. When the system operating frequency is f1, the coupling coefficient k ps It can vary between 0.1837 and 0.2896, that is, two different coupling coefficient fluctuation ranges are connected end to end.

[0184] In summary, when the system operating frequency f2 is within the coupling coefficient k ps When it switches to f1 at 0.1837, the coupling coefficient k ps It can fluctuate between 0.1166 and 0.2896, that is, the coupling coefficient fluctuates within a range close to 250%. The system output power range is 452.38W to 500W, and the output power fluctuation is always within the set 5%. Therefore, the present invention has the ability to output constant power against wide-range fluctuations in the coupling coefficient, and achieves nearly constant power transmission within a wider coupling coefficient fluctuation range.

[0185] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement made to the above embodiments without departing from the content of the technical solution of the present invention, based on the technical essence of the present invention, within the spirit and principles of the present invention, still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for designing wireless charging system parameters to resist wide-range fluctuations in coupling coefficient, characterized in that: The steps include: Step 1: According to the main circuit architecture of the wireless charging system and the actual working conditions, set the system technical indicators, including the DC input voltage U D , preset output power P oset , Battery equivalent load R o , system output power fluctuation ratio δ, system operating frequency f1, primary transmitting coil L p , secondary receiving coil L s ; Step 2: According to the system output power fluctuation ratio δ, the coupling variation multiples β1 and β2 at the system operating frequencies f1 and f2 and the actual coupling variation multiple β0 are calculated respectively; Step 3: Calculate the system operating frequency f2 based on the system operating frequency f1 and its coupling change multiple β1; Step 4: Determine the system power-coupling curve P o (k ps ) in each coupling coefficient, including the minimum working coupling coefficient k min , the extreme coupling coefficient k at the system operating frequency f1 ex1 , critical coupling coefficient k during frequency switching cri 、The extreme coupling coefficient k at the system operating frequency f2 ex2 , maximum working coupling coefficient k max ; Step 5: Complete the adjustment of the parameters of each compensation component and calculate the primary side detuning rates α1 and α2 at the system operating frequencies f1 and f2 respectively.

2. A method for designing wireless charging system parameters to resist wide-range fluctuations in coupling coefficient according to claim 1, characterized in that: The main circuit architecture of the wireless charging system includes a high-frequency inverter circuit, a primary compensation network, a secondary compensation network, and a rectifier and filter circuit; The primary compensation network includes a primary series compensation capacitor C p and the primary transmitting coil L p ; The two output ends of the high-frequency inverter circuit are respectively connected to the two input ends of the primary compensation network in a one-to-one correspondence; The secondary side compensation network includes a secondary side series compensation capacitor C s , secondary loop compensation capacitor C s1 , secondary loop compensation inductor L s1 and the secondary receiving coil L s ; The two input terminals of the rectifier and filter circuit are respectively connected to the two output terminals of the secondary side compensation network in a one-to-one correspondence.

3. The method for designing wireless charging system parameters for resisting wide-range fluctuation of coupling coefficient according to claim 1, characterized in that: The wireless charging system has two operating frequencies f1 and f2, which correspond to different coupling coefficient fluctuation ranges respectively.

4. A method for designing wireless charging system parameters for resisting wide-range fluctuations in 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 primary side series compensation capacitor C in the primary side compensation network p , primary transmitting coil L p The secondary side series compensation capacitor C in the secondary side compensation network constitutes a series detuned network; s , secondary loop compensation capacitor C s1 , secondary loop compensation inductor L s1 , secondary receiving coil L s Form a series resonant network; Specifically: Where: 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.

5. A method for designing wireless charging system parameters for resisting wide-range fluctuations in 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 its value is only related to the quality factor Q of the primary side transmitting coil and the secondary side receiving coil. p , Q s And the coupling coefficient k ps Related, the specific expression is: Where: ξ is the loss coefficient, that is Q p , Q s are the quality factors of the primary transmitting coil and the secondary receiving coil, respectively, ω is the system operating angular frequency, that is, ω = 2πf, f is the system operating frequency, that is, f1 or f2; L p is the self-inductance of the primary transmitting coil, L s is the self-inductance of the secondary receiving coil; R p is the parasitic resistance value of the primary transmitting coil, R s is the parasitic resistance value of the secondary receiving coil; R eq It is the equivalent AC resistance value before the rectifier and filter circuit.

6. The method for designing wireless charging system parameters for resisting wide-range fluctuation of coupling coefficient according to claim 1, characterized in that: The step 1 specifically includes: The definition of the system output power fluctuation ratio δ is: Among them, P omax and P omin are the maximum and minimum power values ​​allowed to be transmitted by the frequency switching-based wireless power transmission system, respectively, and they are stipulated to have the following relationship: Where: P oset The preset output power.

7. The method for designing wireless charging system parameters for resisting wide-range fluctuation of coupling coefficient according to claim 1, characterized in that: The step 2 specifically includes: The definition of the coupling change multiple β1 at the system operating frequency f1 is: Among them, k max is the maximum working coupling coefficient, k cri is the critical coupling coefficient during frequency switching, and the coupling change multiple β1 at the system operating frequency f1 can be calculated by the following formula: Where: δ1 is the system output power fluctuation ratio at the system operating frequency f1; The definition of the coupling change factor β2 at the system operating frequency f2 is: Among them, k cri is the critical coupling coefficient during frequency switching, k min is the minimum working coupling coefficient, and the coupling change multiple β2 under the system working frequency f2 can be calculated by the following formula: Where: δ2 is the system output power fluctuation ratio at the system operating frequency f2; The actual coupling variation factor β0 is defined as: Among them, k max is the maximum working coupling coefficient, k min is the minimum working coupling coefficient, and the actual coupling change multiple β0 is specified to be calculated by the following formula: β0＝β1β2 Where: β1 is the coupling change multiple at the system operating frequency f1, and β2 is the coupling change multiple at the system operating frequency f2.

8. The method for designing wireless charging system parameters for resisting wide-range fluctuation of coupling coefficient according to claim 1, characterized in that: The step three specifically includes: The calculation formula of the system operating frequency f2 is: f2=β1f1 Where: β1 is the coupling change multiple at the system operating frequency f1; f1 is the set system operating frequency.

9. The method for designing wireless charging system parameters for resisting wide-range fluctuation of coupling coefficient according to claim 1, characterized in that: The step 4 specifically includes: The system power-coupling curve P o (k ps ), where the system output power Po increases first and then decreases as the coupling coefficient kps decreases. The specific expression is: Where: B=αL p ; 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; L p is the self-inductance of the primary transmitting coil, L s is the self-inductance of the secondary receiving coil; U D is the voltage value of the DC voltage source, R o is the resistance value of the battery load; The system power-coupling curve P o (k ps ) The calculation formula of the critical coupling coefficient kcri during 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 is the self-inductance of the secondary receiving coil; R o is the resistance value of the battery load, and it is stipulated that it has the following relationship with other coupling coefficients in the curve: Where: β1 is the coupling change multiple at the system operating frequency f1, β2 is the coupling change multiple at the system operating frequency f2; k min is the minimum working coupling coefficient, k ex1 is the extreme coupling coefficient at the system operating frequency f1, k ex2 is the extreme coupling coefficient at the system operating frequency f2, k max is the maximum working coupling coefficient.

10. The method for designing wireless charging system parameters for resisting wide-range fluctuation of coupling coefficient according to claim 1, characterized in that: The step five specifically includes: 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 is: The secondary loop compensation capacitor C in the secondary compensation network s1 The calculation formula is: The secondary loop compensation inductor L in the secondary compensation network s1 The calculation formula is: The calculation formula of the primary side detuning rate α1 at the system operating frequency f1 is: The calculation formula of the primary side detuning rate α2 at the system operating frequency f2 is: Where: ω1 is the working angular frequency of the system operating frequency f1, ω2 is the working 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 is the self-inductance of the primary transmitting coil, L s is the self-inductance of the secondary receiving coil; R o is the resistance value of the battery load; k cri is the critical coupling coefficient during frequency switching.

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