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

Abstract

The invention discloses a wireless charging system parameter design method for resisting wide-range change 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, designing an initial system power-coupling curve and compensation element parameters according to the set technical indexes; and 3, judging whether the coupling coefficient kps is within the initial coupling coefficient change range or not. If yes, the duty ratio is the initial duty ratio D0, and the process is ended; if not, entering the step 4; and 4, judging whether the coupling coefficient kps is greater than the initial maximum coupling coefficient kmax0 or not. If yes, performing right side range judgment on the coupling coefficient kps, determining an n value, designing a corresponding right side nth duty ratio DRn, and ending; and if not, performing left side range judgment on the coupling coefficient kps, determining an n value, designing a corresponding left side nth duty ratio DLn, and ending. According to the invention, the output power of the system has small fluctuation when the coupling coefficient changes in a wide range.

Description

Technical Field

[0001] The present invention relates to a wireless charging system parameter design method, in particular to a wireless charging system parameter design method with resistance to wide range variation of coupling coefficient, belonging to the technical field of wireless power transmission. 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, and has been widely used in portable electronic devices, implantable medical devices, underwater detectors and other fields. However, in actual applications, the primary transmitting coil and the secondary receiving coil are inevitably misaligned, and the mutual inductance and coupling parameters between the coils change dramatically, which in turn affects the stability of power transmission in the IPT system.

[0003] To this end, domestic and foreign research teams mainly start their research from the aspects of magnetic coupling mechanism design and compensation topology optimization. For example, the University of Hong Kong proposed a combination structure consisting of three layers of hexagonal coil arrays placed in an interlaced manner, which constructs a uniform magnetic field by superimposing magnetic density, effectively increasing the coupling area, but as a compromise, it increases the consumables of the coil and sacrifices the system transmission efficiency. Furthermore, some scholars have proposed a compensation topology optimization method. San Diego State University in the United States proposed a dual-coupled DLCC compensation topology, which effectively improves the system's anti-offset performance by coupling bilateral compensation inductors with energy coils. However, the proposed method is complex in design, and when the offset distance is far, the system output fluctuation is still large. In addition, more compensation components, especially inductor coils, are not conducive to the compact design of the receiving side, which leads to an increase in system cost, volume and weight. Summary of the invention

[0004] In order to overcome the defects and shortcomings of the prior art, the present invention further proposes a wireless charging system parameter design method that is resistant to wide-range changes in coupling coefficients, which can ensure that the system output power fluctuates less when the coupling coefficient changes in a wide range.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations, the wireless charging system comprising a DC voltage source U D , full-bridge inverter circuit, primary resonant network, secondary resonant network, rectifier filter circuit, DC-DC conversion circuit and battery equivalent load R o The two input terminals of the full-bridge inverter circuit are connected to the DC voltage source U DThe two output ends of the full-bridge inverter circuit are connected to the two input ends of the primary resonant network in a one-to-one correspondence. The primary resonant network includes a primary first transmitting coil L p1 , the primary second transmitting coil L p2 , primary side series compensation capacitor C p1 , primary circuit compensation capacitor C p2 and primary branch compensation components, the secondary resonant network includes a secondary receiving coil L s And the secondary side series compensation capacitor C s The primary resonant network and the secondary resonant network are coupled by mutual inductance, the two input ends of the rectifier filter circuit are connected one-to-one with the two output ends of the secondary resonant network, the two input ends of the direct-to-direct conversion circuit are connected one-to-one with the two output ends of the rectifier filter circuit, and the two input ends of the direct-to-direct conversion circuit are connected to the battery equivalent load R o The method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations is implemented by the following steps:

[0007] S1: Setting the technical indicators of the wireless charging system, the technical indicators specifically include: DC input voltage U D , preset output power P oset , Battery equivalent load R o , system output power fluctuation ratio δ, system operating frequency f, primary first transmitting coil L p1 , the primary second transmitting coil L p2 , secondary receiving coil L s , initial extreme coupling coefficient k ex0 ;

[0008] S2: According to the technical indicators set in S1, design the initial system power-coupling curve and the parameters of the compensation components in the wireless charging system. The parameters specifically include: coupling change multiple β, initial minimum coupling coefficient k min0 , initial maximum coupling coefficient k max0 , primary side series compensation capacitor C p1 , primary circuit compensation capacitor C p2 , primary branch compensation element impedance jX, secondary side series compensation capacitor C s ;

[0009] S3: Determine the coupling coefficient k ps Is it within the initial coupling coefficient variation range [k min0 , k max0 ], if so, obtain the initial duty cycle D0 and the initial equivalent AC load R before the system rectifier filter circuit eq0 , end; if not, enter S4;

[0010] S4: Determine the coupling coefficient k ps Is it greater than the initial maximum coupling coefficient k max0 If so, first calculate the coupling coefficient k ps Determine the right range and then design the corresponding right nth duty cycle D Rn , get the nth equivalent AC load R on the right side before the system rectifier and filter circuit eqRn , the right side nth extreme coupling coefficient k exRn and the nth largest coupling coefficient k on the right maxRn , end; if not, first calculate the coupling coefficient k ps Determine the left range and then design the corresponding left nth duty cycle D Ln , get the nth equivalent AC load R on the left side before the system rectifier and filter circuit eqLn , the left side nth extreme coupling coefficient k exLn , the nth minimum coupling coefficient k on the left minLn ,Finish.

[0011] Furthermore, the direct-to-direct conversion circuit is a buck-boost circuit.

[0012] Furthermore, the system output power fluctuation ratio δ in S1 is defined as follows:

[0013]

[0014] Among them, P omax and P omin They are the maximum and minimum values ​​of the power allowed to be transmitted by the wireless charging system, and they are stipulated to have the following relationship:

[0015]

[0016] Where P oset The preset output power.

[0017] Furthermore, the initial system power-coupling curve P described in S2 o (k ps0 ) is expressed as follows:

[0018]

[0019] Where: ω is the system operating angular frequency, L p The first transmitting coil L is the primary side p1 Or the primary second transmitting coil L p2 The self-inductance value, let L p =L p1 =L p2 , L s is the self-inductance of the secondary receiving coil, U Dis the voltage value of the DC voltage source, R o is the resistance value of the battery equivalent load, k p1s0 is the initial coupling coefficient between the primary first transmitting coil and the secondary receiving coil, k p2s0 is the initial coupling coefficient between the primary second transmitting coil and the secondary receiving coil, let k ps0 =k p1s0 =k p2s0 , and k ps0 ∈[k min0 , k max0 ],k min0 is the initial minimum coupling coefficient, k max0 is the initial maximum coupling coefficient.

[0020] Furthermore, the primary branch compensation element is a primary branch compensation capacitor C x Or the primary branch compensation inductor L x , the selection rules of specific device characteristics are as follows:

[0021]

[0022] Among them, M p1s0 is the initial main coupling mutual inductance between the primary first transmitting coil and the secondary receiving coil, M p2s0 is the initial main coupling mutual inductance between the primary second transmitting coil and the secondary receiving coil, that is,

[0023] Furthermore, the coupling change factor β in S2 is expressed as follows:

[0024]

[0025] Furthermore, the initial minimum coupling coefficient k in S2 is min0 and the initial maximum coupling coefficient k max0 The expression is as follows:

[0026]

[0027] Furthermore, the primary side series compensation capacitor C in S2 p1 , the primary circuit compensation capacitor C p2 , the impedance jX of the primary branch compensation element, and the secondary side series compensation capacitor C s The expression is as follows:

[0028]

[0029] Furthermore, the initial duty cycle D0 in S3 is when the coupling coefficient k psGreater than or equal to the initial minimum coupling coefficient k min0 , and is less than or equal to the initial maximum coupling coefficient k max0 When the control square wave duty cycle of the DC-DC conversion circuit is , the initial duty cycle D0 and the initial equivalent AC load R before the system rectifier filter circuit are equal to eq0 The expression is as follows:

[0030]

[0031] Where: R o is the resistance value of the battery equivalent load.

[0032] Furthermore, the right nth duty cycle D described in S4 Rn When the coupling coefficient k ps Greater than the initial maximum coupling coefficient k max0 When the control square wave duty cycle of the DC-DC conversion circuit is , where n is a positive integer, it must satisfy the range judgment formula on the right:

[0033]

[0034] in, The symbol indicates rounding up.

[0035] At this time, the right side nth duty cycle D Rn , the nth equivalent AC load R on the right before the rectifier and filter circuit of the system eqRn , the right side nth extreme coupling coefficient k exRn , the right side nth maximum coupling coefficient k maxRn The expression is as follows:

[0036]

[0037] Furthermore, the left nth duty cycle D in S4 Ln When the coupling coefficient k ps Less than the initial minimum coupling coefficient k min0 When the control square wave duty cycle of the DC-DC conversion circuit is , where n is a positive integer, it must satisfy the left range judgment formula:

[0038]

[0039] in, The symbol indicates rounding up.

[0040] At this time, the left nth duty cycle D Ln , the nth equivalent AC load R on the left before the rectifier and filter circuit of the system eqLn , the left side nth extreme coupling coefficient k exLn , the left nth minimum coupling coefficient k minLnThe expression is as follows:

[0041]

[0042] The beneficial effects of the present invention are:

[0043] 1. The present invention can change the equivalent AC load before the system rectifier and filter circuit by switching the duty cycle of the direct-to-direct conversion circuit at a fixed operating frequency, thereby connecting multiple coupling coefficient variation ranges in sequence to ensure that the system output power fluctuates less when the coupling coefficient varies in a wide range.

[0044] 2. The parameter design method of a wireless charging system with a wide range of anti-coupling coefficient changes provided by the present invention does not require any additional loop iteration or optimization algorithm, and can directly perform assignment calculations, thereby achieving rapid determination of all system parameters and simplifying the system parameter design steps.

[0045] 3. The parameter design method of a wireless charging system with a wide range of resistant coupling coefficient changes provided by the present invention can be extended and applied to other low-order or high-order compensation topologies, that is, it is suitable for a class of compensation topologies with similar output characteristics, such as: primary-side detuned SS compensation topology, detuned LCC-S compensation topology. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flow chart of a method for designing parameters of a wireless charging system that resists wide-range variation of coupling coefficients according to the present invention;

[0047] Figure 2 It is a schematic diagram of the main circuit architecture of the wireless charging system of the present invention;

[0048] Figure 3 It is a schematic diagram of the design of the curve of the output power of the system of the present invention changing with the coupling coefficient;

[0049] Figure 4 It is a theoretical calculation diagram of the output power of the system of the present invention changing with the coupling coefficient. DETAILED DESCRIPTION

[0050] Specific implementation method 1: Combination Figure 1-4 The present embodiment is described. The present embodiment describes a method for designing parameters of a wireless charging system that is resistant to wide-range variation in coupling coefficient.

[0051] The wireless charging system comprises a DC voltage source U D , full-bridge inverter circuit, primary resonant network, secondary resonant network, rectifier filter circuit, DC-DC conversion circuit and battery equivalent load R o The two input terminals of the full-bridge inverter circuit are connected to the DC voltage source U DThe two output ends of the full-bridge inverter circuit are connected to the two input ends of the primary resonant network in a one-to-one correspondence. The primary resonant network includes a primary first transmitting coil L p1 , the primary second transmitting coil L p2 , primary side series compensation capacitor C p1 , primary circuit compensation capacitor C p2 and a primary branch compensation element, preferably, the primary branch compensation element is a primary branch compensation capacitor C x Or the primary branch compensation inductor L x The secondary resonant network includes a secondary receiving coil L s And the secondary side series compensation capacitor C s The primary resonant network and the secondary resonant network are coupled by mutual inductance, the two input ends of the rectifier filter circuit are connected one-to-one with the two output ends of the secondary resonant network, the two input ends of the direct-to-direct conversion circuit are connected one-to-one with the two output ends of the rectifier filter circuit, and the two input ends of the direct-to-direct conversion circuit are connected to the battery equivalent load R o Preferably, the direct-to-direct conversion circuit is a buck-boost circuit, which can be used in the full coupling coefficient variation range with the parameter design method, that is, the coupling coefficient k ps Between 0 and 1, the system realizes the constant power output characteristic of anti-coupling coefficient change.

[0052] Specific as Figure 2 As shown, the main circuit architecture of the wireless charging system specifically includes: a full-bridge inverter circuit, a primary resonant network, a secondary resonant network, a rectifier filter circuit, and a direct-to-direct conversion circuit; the primary resonant network is composed of a primary first transmitting coil L p1 , the primary second transmitting coil L p2 , primary side series compensation capacitor C p1 , primary circuit compensation capacitor C p2 , the primary branch compensation element, the primary branch compensation element can be the primary branch compensation capacitor C x Or the primary branch compensation inductor L x The two output ends of the full-bridge inverter circuit are connected to the two input ends of the primary resonant network in a one-to-one correspondence, and the two input ends are connected to the DC voltage source U D The secondary resonant network is connected to the secondary receiving coil L s , Secondary side series compensation capacitor C s The two input ends of the rectifier filter circuit are connected to the two output ends of the secondary resonant network in a one-to-one correspondence; the direct-to-direct conversion circuit is a Buck-Boost circuit, whose two input ends are connected to the two output ends of the rectifier filter circuit in a one-to-one correspondence, and whose two input ends are connected to the battery equivalent load Ro connected.

[0053] like Figure 1 As shown, the method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations is implemented by the following steps:

[0054] S1: According to the main circuit architecture of the wireless charging system and the actual working conditions, the technical indicators of the wireless charging system are set. The technical indicators specifically include: DC input voltage U D , preset output power P oset , Battery equivalent load R o , system output power fluctuation ratio δ, system operating frequency f, primary first transmitting coil L p1 , the primary second transmitting coil L p2 , secondary receiving coil L s and the initial extreme coupling coefficient k ex0 .

[0055] The definition of the system output power fluctuation ratio δ is:

[0056]

[0057] Among them, P omax and P omin They are the maximum and minimum values ​​of the power allowed to be transmitted by the wireless charging system, and they are stipulated to have the following relationship:

[0058]

[0059] Where: P oset The preset output power.

[0060] S2: According to the technical indicators set in S1, design the initial system power-coupling curve and the parameters of the compensation components in the wireless charging system. The parameters specifically include: coupling change multiple β, initial minimum coupling coefficient k min0 , initial maximum coupling coefficient k max0 , primary side series compensation capacitor C p1 , primary circuit compensation capacitor C p2 , the primary branch compensation element impedance jX and the secondary side series compensation capacitor C s .

[0061] like Figure 3 As shown, the initial system power-coupling curve P o (k ps0 ), where the system output power P o With the initial coupling coefficient k ps0 Decrease, its value increases first and then decreases, the specific expression is:

[0062]

[0063] Where: ω is the system operating angular frequency; L p The first transmitting coil L is the primary side p1 Or the primary second transmitting coil L p2 The self-inductance value, let L p =L p1 =L p2 , 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 equivalent load; k p1s0 is the initial coupling coefficient between the primary first transmitting coil and the secondary receiving coil, k p2s0 is the initial coupling coefficient between the primary second transmitting coil and the secondary receiving coil, let k ps0 =k p1s0 =k p2s0 , and k ps0 ∈[k min0 , k max0 ],k min0 is the initial minimum coupling coefficient, k max0 is the initial maximum coupling coefficient; jX is the impedance of the primary branch compensation element, and:

[0064]

[0065] Among them, L x is the primary branch compensation inductor, C x is the primary branch compensation capacitor, M p1s0 is the initial main coupling mutual inductance between the primary first transmitting coil and the secondary receiving coil, M p2s0 is the initial main coupling mutual inductance between the primary second transmitting coil and the secondary receiving coil, that is,

[0066] The coupling change factor β can be calculated by the following formula:

[0067]

[0068] Among them, δ is the system output power fluctuation ratio.

[0069] The initial minimum coupling coefficient k min0 , initial maximum coupling coefficient k max0 Respectively expressed as:

[0070]

[0071] Among them, k ex0 is the initial extreme coupling coefficient.

[0072] The primary side series compensation capacitor C p1 , primary circuit compensation capacitor C p2 , primary branch compensation element impedance jX, secondary side series compensation capacitor C s Respectively expressed as:

[0073]

[0074] S3: Determine the coupling coefficient k ps Is it within the initial coupling coefficient variation range [k min0 , k max0 ], if so, obtain the initial duty cycle D0 and the initial equivalent AC load R before the system rectifier filter circuit eq0 , end; if not, enter S4.

[0075] like Figure 3 As shown, when the coupling coefficient k ps In the initial coupling coefficient variation range [k min0 , k max0 ], that is, the coupling coefficient k ps Greater than or equal to the initial minimum coupling coefficient k min0 , and is less than or equal to the initial maximum coupling coefficient k max0 When the control square wave duty cycle D of the DC-DC conversion circuit is called the initial duty cycle D0; at this time (coupling coefficient k ps Greater than or equal to the initial minimum coupling coefficient k min0 , and is less than or equal to the initial maximum coupling coefficient k max0 The initial duty cycle D0 and the initial equivalent AC load R before the system rectifier filter circuit eq0 Respectively expressed as:

[0076]

[0077] Where: R o is the resistance value of the battery equivalent load.

[0078] S4: Determine the coupling coefficient k ps Is it greater than the initial maximum coupling coefficient k max0 If so, first calculate the coupling coefficient k ps Determine the right range and then design the corresponding right nth duty cycle D Rn , get the nth equivalent AC load R on the right side before the system rectifier and filter circuit eqRn , the right side nth extreme coupling coefficient k exRn and the nth largest coupling coefficient k on the right maxRn , end; if not, first calculate the coupling coefficient k psDetermine the left range and then design the corresponding left nth duty cycle D Ln , get the nth equivalent AC load R on the left side before the system rectifier and filter circuit eqLn , the left side nth extreme coupling coefficient k exLn , the nth minimum coupling coefficient k on the left minLn ,Finish.

[0079] like Figure 3 As shown, when the coupling coefficient k ps In the initial coupling coefficient variation range [k min0 , k max0 ], that is, the coupling coefficient k ps Greater than the initial maximum coupling coefficient k max0 When the control square wave duty cycle D of the DC-DC conversion circuit is called the nth duty cycle D on the right side Rn , where n must satisfy the right-hand range judgment formula:

[0080]

[0081] At this time (coupling coefficient k ps Greater than the initial maximum coupling coefficient k max0 When) the nth duty cycle on the right side is D Rn 、The nth equivalent AC load R on the right before the system rectifier and filter circuit eqRn , the right side nth extreme coupling coefficient k exRn , the nth largest coupling coefficient k on the right maxRn Respectively expressed as:

[0082]

[0083] like Figure 3 As shown, when the coupling coefficient k ps In the initial coupling coefficient variation range [k min0 , k max0 ] on the left side, that is, the coupling coefficient k ps Less than the initial minimum coupling coefficient k min0 When the control square wave duty cycle D of the DC-DC conversion circuit is called the left nth duty cycle D Ln , where n must satisfy the left range judgment formula:

[0084]

[0085] At this time (coupling coefficient k ps Less than the initial minimum coupling coefficient k min0 When) the left side nth duty cycle D Ln , the nth equivalent AC load R on the left before the system rectifier filter circuit eqLn , the left side nth extreme coupling coefficient k exLn, the nth minimum coupling coefficient k on the left minLn Respectively expressed as:

[0086]

[0087] in, The symbol indicates rounding up, for example: n is a positive integer, i.e. 1, 2, 3...; β is the coupling change multiple; R eq0 is the initial equivalent AC load before the system rectifier and filter circuit; k ex0 is the initial extreme coupling coefficient.

[0088] Specifically, in order to verify the correctness and feasibility of the parameter design method for the wireless charging system with a wide range of anti-coupling coefficient variations, a detailed parameter design process is given below in combination with a design example:

[0089] First, the system technical indicators are given, as shown in Table 1:

[0090] Table 1 System technical indicators

[0091]

[0092] Then, according to the technical indicators shown in Table 1, the initial system power-coupling curve and compensation element parameters are designed. Specifically, they include: coupling change multiple β, initial minimum coupling coefficient k min0 , initial maximum coupling coefficient k max0 , primary side series compensation capacitor C p1 , primary circuit compensation capacitor C p2 , the impedance of the primary branch compensation element jX (here the primary branch compensation inductor L x For example), the secondary side series compensation capacitor C s , as shown in Table 2:

[0093] Table 2 Initial system power-coupling curve and compensation component parameters

[0094]

[0095] Then, when the coupling coefficient k ps In the initial coupling coefficient variation range [k min0 , k max0 ], that is, the coupling coefficient k ps Greater than or equal to the initial minimum coupling coefficient k min0 , and is less than or equal to the initial maximum coupling coefficient k max0 At this time, the initial duty cycle D0 and the initial equivalent AC load R before the system rectifier filter circuit eq0 Respectively expressed as:

[0096]

[0097] Furthermore, in order to more intuitively demonstrate that the present invention has the ability to output constant power against wide-range variations in coupling coefficient, when the coupling coefficient k ps In the initial coupling coefficient variation range [k min0 , k max0 ], n is 1 and 2 respectively. Therefore, the first duty cycle D on the right side can be obtained by equation (10) and equation (12) respectively. R1 , the first equivalent AC load R on the right before the system rectifier and filter circuit eqR1 , the first extreme coupling coefficient k on the right exR1 , the first maximum coupling coefficient k on the right maxR1 ; The second duty cycle on the right is D R2 , the second equivalent AC load R on the right before the system rectifier filter circuit eqR2 , the second extreme coupling coefficient k on the right exR2 , the second largest coupling coefficient k on the right maxR2 ; Left first duty cycle D L1 , the first equivalent AC load R on the left before the system rectifier filter circuit eqL1 , the first extreme coupling coefficient k on the left exL1 , the first minimum coupling coefficient k on the left minL1 ; The second duty cycle on the left is D L2 , the second equivalent AC load R on the left before the system rectifier filter circuit eqL2 , the second extreme coupling coefficient k on the left exL2 , the second minimum coupling coefficient k on the left minL2 , as shown in Table 3:

[0098] Table 3 Summary of all parameters

[0099]

[0100] Finally, based on the initial system power-coupling curve P o (k ps0 ) expression (3), and with the help of Mathematica mathematical analysis software, we get Figure 4 The system output power P shown o With the coupling coefficient k ps Theoretical calculation diagram of the change curve. Figure 3 and Figure 4 It can be seen that in order to meet the technical indicator requirement of the system output power fluctuation ratio δ of 5%, when the control square wave duty cycle D of the DC-DC conversion circuit is the second duty cycle D on the left side L2 When the coupling coefficient k psIt can vary between 0.0962 and 0.1516; when the control square wave duty cycle D of the DC-DC conversion circuit is the first duty cycle D on the left L1 When the coupling coefficient k ps It can vary between 0.1516 and 0.2390. When the control square wave duty cycle D of the DC-DC conversion circuit is the initial duty cycle D0, the coupling coefficient k ps It can vary between 0.2390 and 0.3766; when the control square wave duty cycle D of the DC-DC conversion circuit is the first duty cycle D on the right R1 When the coupling coefficient k ps It can vary between 0.3766 and 0.5936; when the control square wave duty cycle D of the DC-DC conversion circuit is the second duty cycle D on the right R2 When the coupling coefficient k ps It can vary between 0.5936 and 0.9355, that is, 5 different coupling coefficient variation ranges are connected in sequence.

[0101] In summary, when the control square wave duty cycle D of the DC-DC conversion circuit is in accordance with the designed D R1 , D R2 , D0, D L1 , D L2 When switching between ps It can vary between 0.0962 and 0.9355, that is, within the range of the coupling coefficient variation of nearly 10 times, the system output power range is 904.76W to 1000W, and the system output power fluctuation is always within the set 5%. Therefore, the present invention has the ability to output constant power against wide-range variation of the coupling coefficient, ensuring that the system output power fluctuates less when the coupling coefficient varies in a wide range.

[0102] 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 variation of coupling coefficient, characterized in that: The wireless charging system comprises a DC voltage source U D , full-bridge inverter circuit, primary resonant network, secondary resonant network, rectifier filter circuit, DC-DC conversion circuit and battery equivalent load R o The two input terminals of the full-bridge inverter circuit are connected to the DC voltage source U D The two output ends of the full-bridge inverter circuit are connected to the two input ends of the primary resonant network in a one-to-one correspondence. The primary resonant network includes a primary first transmitting coil L p1 , the primary second transmitting coil L p2 , primary side series compensation capacitor C p1 , primary circuit compensation capacitor C p2 and primary branch compensation components, the secondary resonant network includes a secondary receiving coil L s And the secondary side series compensation capacitor C s The primary resonant network and the secondary resonant network are coupled by mutual inductance, the two input ends of the rectifier filter circuit are connected one-to-one with the two output ends of the secondary resonant network, the two input ends of the direct-to-direct conversion circuit are connected one-to-one with the two output ends of the rectifier filter circuit, and the two input ends of the direct-to-direct conversion circuit are connected to the battery equivalent load R o The method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations is implemented by the following steps: S1: Setting the technical indicators of the wireless charging system, the technical indicators specifically include: DC input voltage U D , preset output power P oset , Battery equivalent load R o , system output power fluctuation ratio δ, system operating frequency f, primary first transmitting coil L p1 , the primary second transmitting coil L p2 , secondary receiving coil L s and the initial extreme coupling coefficient k ex0 ; S2: According to the technical indicators set in S1, design the initial system power-coupling curve and the parameters of the compensation components in the wireless charging system. The parameters specifically include: coupling change multiple β, initial minimum coupling coefficient k min0 , initial maximum coupling coefficient k max0 , primary side series compensation capacitor C p1 , primary circuit compensation capacitor C p2 , the primary branch compensation element impedance jX and the secondary side series compensation capacitor C s ; S3: Determine the coupling coefficient k ps Is it within the initial coupling coefficient variation range [k min0 , k max0 ], if so, obtain the initial duty cycle D0 and the initial equivalent AC load R before the system rectifier filter circuit eq0 , end; if not, enter S4; S4: Determine the coupling coefficient k ps Is it greater than the initial maximum coupling coefficient k max0 If so, first calculate the coupling coefficient k ps Determine the right range and then design the corresponding right nth duty cycle D Rn , get the nth equivalent AC load R on the right side before the system rectifier and filter circuit eqRn , the right side nth extreme coupling coefficient k exRn and the nth largest coupling coefficient k on the right maxRn , end; if not, first calculate the coupling coefficient k ps Determine the left range and then design the corresponding left nth duty cycle D Ln , get the nth equivalent AC load R on the left side before the system rectifier and filter circuit eqLn , the left side nth extreme coupling coefficient k exLn , the nth minimum coupling coefficient k on the left minLn ,Finish.

2. A method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations according to claim 1, characterized in that: The definition of the system output power fluctuation ratio δ in S1 is as follows: Among them, P omax and P omin They are the maximum and minimum values ​​of the power allowed to be transmitted by the wireless charging system, and they are stipulated to have the following relationship: Where P oset The preset output power.

3. A method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations according to claim 2, characterized in that: The initial system power-coupling curve P described in S2 o (k ps0 ) is expressed as follows: Where: ω is the system operating angular frequency, L p The first transmitting coil L is the primary side p1 Or the primary second transmitting coil L p2 The self-inductance value, let L p =L p1 =L p2 , 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 equivalent load, k p1s0 is the initial coupling coefficient between the primary first transmitting coil and the secondary receiving coil, k p2s0 is the initial coupling coefficient between the primary second transmitting coil and the secondary receiving coil, let k ps0 =k p1s0 =k p2s0 , and k ps0 ∈[k min0 , k max0 ],k min0 is the initial minimum coupling coefficient, k max0 is the initial maximum coupling coefficient.

4. A method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations according to claim 3, characterized in that: The primary branch compensation element is a primary branch compensation capacitor C x Or the primary branch compensation inductor L x , the selection rules of specific device characteristics are as follows: Among them, M p1s0 is the initial main coupling mutual inductance between the primary first transmitting coil and the secondary receiving coil, M p2s0 is the initial main coupling mutual inductance between the primary second transmitting coil and the secondary receiving coil, that is, 5. The method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations according to claim 3, characterized in that: The expression of the coupling change factor β described in S2 is as follows:

6. A method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations according to claim 5, characterized in that: The initial minimum coupling coefficient k is described in S2 min0 and the initial maximum coupling coefficient k max0 The expression is as follows:

7. The method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations according to claim 3, characterized in that: The primary side series compensation capacitor C p1 , the primary circuit compensation capacitor C p2 , the impedance jX of the primary branch compensation element, and the secondary side series compensation capacitor C s The expression is as follows: Where X is the imaginary part of the impedance of the primary branch compensation element, that is, 8. The method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations according to claim 1, characterized in that: The initial duty cycle D0 in S3 is when the coupling coefficient k ps Greater than or equal to the initial minimum coupling coefficient k min0 , and is less than or equal to the initial maximum coupling coefficient k max0 When the control square wave duty cycle of the DC-DC conversion circuit is , the initial duty cycle D0 and the initial equivalent AC load R before the system rectifier filter circuit are equal to eq0 The expression is as follows: Where: R o is the resistance value of the battery equivalent load.

9. The method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations according to claim 1, characterized in that: The right nth duty ratio D described in S4 Rn When the coupling coefficient k ps Greater than the initial maximum coupling coefficient k max0 When the control square wave duty cycle of the DC-DC conversion circuit is , where n is a positive integer, it must satisfy the range judgment formula on the right: in, The symbol indicates rounding up. At this time, the right side nth duty cycle D Rn , the nth equivalent AC load R on the right before the rectifier and filter circuit of the system eqRn , the right side nth extreme coupling coefficient k exRn , the right side nth maximum coupling coefficient k maxRn The expression is as follows:

10. The method for designing parameters of a wireless charging system with a wide range of anti-coupling coefficient variations according to claim 1, characterized in that: The left nth duty ratio D described in S4 Ln When the coupling coefficient k ps Less than the initial minimum coupling coefficient k min0 When the control square wave duty cycle of the DC-DC conversion circuit is , where n is a positive integer, it must satisfy the left range judgment formula: in, The symbol indicates rounding up. At this time, the left nth duty cycle D Ln , the nth equivalent AC load R on the left before the rectifier and filter circuit of the system eqLn , the left side nth extreme coupling coefficient k exLn , the left nth minimum coupling coefficient k minLn The expression is as follows:

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