A WPT system coupling coil and compensation parameter design method

Abstract

The present invention relates to the technical field of wireless power transmission, and particularly relates to a design method for a coupling coil and compensation parameters of a WPT system. The method includes the steps of: giving the initial values of Q in , Q O , and L Pr , that is, Q in‑s , Q O‑s , and L Pr‑s ; determining the boundary conditions to obtain the design parameters of the compensation and coupling coils that meet the constraints; through simulation, enumerating and selecting the design parameters of the compensation and coupling coils that meet the constraints; substituting into the efficiency constraint formula to determine whether the set constraint threshold is reached; selecting the design parameters of the compensation and coupling coils with the minimum comprehensive index of patience for the constraint threshold as the output. The present invention analyzes and quantitatively analyzes the influence of all potential variable parameters on the performance of the WPT system; adopts the parameter scanning method to evaluate the changes in the self-inductance and mutual inductance of the square coil; and proposes the WPT system of the present invention, which can effectively compensate and couple the deviation tolerance of relevant parameters in practice.

Description

Technical Field

[0001] The present invention relates to the field of wireless power transmission technology, and in particular to a WPT system coupling coil and compensation parameter design method. Background Art

[0002] A typical wireless power transfer (WPT) system usually consists of a grid-side rectifier, a primary inverter, a compensation network, a coupling coil, and a secondary rectifier. The primary inverter converts DC power into high-frequency AC power, while the rectifier reverses this process. The high-frequency AC flows through the compensation circuit and the coupler to achieve contactless transmission of electrical energy. The compensation network usually consists of various types of capacitors and inductors connected in series and in parallel. The resonance between the compensation inductor and capacitor is crucial to reducing reactive power and improving the transmission efficiency of the WPT system.

[0003] However, these compensation capacitors and inductors will have deviations in actual applications, deviating from their expected values. For compensation capacitors, the capacitance parameters will change due to manufacturing precision issues, temperature rise and aging. For compensation inductors, manufacturing precision and lead length differences will also cause differences between actual values ​​and designed values. In addition, the misalignment of the coupling coil position will not only cause the mutual inductance to change, but also cause the self-inductance of the coil to change due to magnetism and the aluminum shielding plate. Therefore, deviations in compensation and coupling related parameters are inevitable and unpredictable, resulting in detuning of the WPT system, the output power cannot meet the load requirements, and the system reactive power increases and the transmission efficiency decreases. At the same time, the voltage and current of the resonant element may exceed the safety threshold, resulting in insulation failure or even system damage. Therefore, it is necessary to analyze the impact of parameter deviation on the WPT system and develop a design process for WPT systems with high parameter deviation tolerance.

[0004] Most of the current deviation technologies for compensation and coupling parameters of WPT systems only focus on the partial deviation effects, such as analyzing the impedance angle, output power and transmission efficiency of the LCC-S topology as the capacitor errors change, or comparing the sensitivity of transconductance, input angle and voltage gain to the compensation errors between various compensation networks. However, for the sake of simplicity, these technologies all assume that the compensation errors do not occur at the same time, which is inconsistent with the actual working conditions. In addition, the above research is based on the determination of coil parameters and constant load resistance, and does not discuss the factors and improvement measures that affect the tolerance of compensation and coupling related parameters.

[0005] There are also related technologies that propose controllable capacitors, which have the potential to achieve the desired compensation and eliminate compensation errors. However, the transmission efficiency and reliability will be reduced because a controlled capacitor requires one or two additional power switches, and the cost of the WPT system will also increase. In addition, it is also difficult to simply and accurately measure the changes in the self-inductance and mutual inductance of the coil. Therefore, a simple and low-cost method must be found to improve the tolerance of the compensation and coupling-related parameter deviations of the WPT system.

[0006] There are three methods for designing coupling coils, namely design flowcharts, parameter scanning, and evolutionary algorithms. Since there are many factors that affect the performance of coupling coils, design flowcharts usually result in suboptimal designs and can only achieve a single optimization goal. Parameter scanning and evolutionary algorithms aim to achieve multi-objective optimization. However, the existing technology has not yet clearly analyzed the impact of compensation and coupling-related parameter deviations on the system. In practice, traditional design methods perform poorly in terms of tolerance for compensation and coupling-related parameter deviations.

[0007] In order to solve the above problems, after evaluating the impact of parameter changes in the WPT system on system characteristics, this technology proposes a WPT system coupling coil and compensation parameter design method and process based on compensation and coupling related parameter deviation considerations. Summary of the invention

[0008] The purpose of the present invention is to provide a WPT system coupling coil and compensation parameter design method, which is used to solve the prior art problems mentioned in the background technology.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A WPT system coupling coil and compensation parameter design method, comprising the following steps:

[0011] By analyzing the deviation characteristics, the inverter quality factor Q is given in The initial value is denoted as Q in-s , Load quality factor Q O Q O-s , the self-inductance of the primary coil L P The primary series compensation inductor L r The ratio L Pr The initial value is denoted as L Pr-s ;

[0012] According to the boundary conditions required by the working conditions and the determined Q in , Q O , L Pr The initial value of is obtained to obtain the design parameters of the compensation and coupling coils that meet the constraints;

[0013] Through simulation, the design parameters of compensation and coupling coils that meet the constraints are selected in groups;

[0014] Substitute the selected compensation and coupling coil design parameters into the efficiency constraint formula to determine whether they meet the set constraint threshold; if they meet, they are retained; if not, they are discarded;

[0015] The tolerance comprehensive index of the compensation and coupling coil design parameters that reach the set constraint threshold is obtained, and the compensation and coupling coil design parameters of the constraint threshold with the smallest tolerance comprehensive index are selected as output.

[0016] Furthermore, the boundary conditions at least include: input voltage and output power.

[0017] Furthermore, the compensation and coupling coil design parameters include: the self-inductance L of the primary coil P The upper limit value of the secondary coil self-inductance L S The upper limit value of , the lower limit value of mutual inductance M.

[0018] Furthermore, the simulation is performed by ANSYS software.

[0019] Furthermore, the efficiency constraint formula is:

[0020]

[0021] Among them, I S is the RMS value of the secondary coil current, R E is the equivalent load resistance; P Lr ,、 P LP , P LS , P Cr , P CP , and P CS There are three inductance components L r , L P and L S and three compensation capacitors C r , C P and C S The loss of Q r , Q P , Q S is the quality factor of the primary compensation inductor, primary coil, and secondary coil; L Pr YesL P and L r ratio; tanδ is the dissipation factor of the capacitor; Q in and Q O They are defined as the inverter quality factor and the load quality factor respectively, and are obtained by the following formula:

[0022]

[0023] Where ω is the operating frequency and M is the mutual inductance.

[0024] Furthermore, the constraint threshold is 90%.

[0025] Furthermore, the tolerance comprehensive index is defined as:

[0026]

[0027] Among them, α, β, γ are weight coefficients; k US-max and k US-min It is k US The maximum and minimum values ​​of λ min The minimum value of the system input power factor; Δη max The maximum value of the system transmission power change;

[0028] Among them, k US It is expressed as:

[0029]

[0030] Where j is an imaginary unit; α is expressed as:

[0031]

[0032] k RE K is the ratio of the rated equivalent load resistance to the actual load resistance under constant output power condition; UCr-max , K UCp-max and K UCs They are respectively expressed as: the maximum value of the voltage rise ratio of the primary parallel compensation capacitor, the primary series compensation capacitor and the secondary series compensation capacitor.

[0033] The present invention has at least the following beneficial effects:

[0034] (1) The present invention analyzes and quantifies the impact of all potential variable parameters (i.e., capacitance, compensation inductance, coil self-inductance, and mutual inductance) on the performance of the WPT system. In addition, the analysis is performed under the condition of constant output power, because the battery voltage can be considered as a constant in a short period of time, and the output power of the WPT system remains essentially unchanged during constant current charging.

[0035] (2) The present invention uses three design degrees of freedom, namely, the inverter quality factor, the load quality factor, and the ratio of the primary coil self-inductance to the compensation inductance, to evaluate the influence of system parameters on the deviation tolerance of compensation and coupling related parameters. The analysis results show that a well-designed coupler helps to improve the variation tolerance of compensation and coupling related parameters.

[0036] (3) The present invention adopts parameter scanning method to evaluate the changes of self-inductance and mutual inductance of square coils; some guidelines are proposed to design the WPT system of the present invention, which can effectively compensate and couple the relevant parameter deviation tolerance in practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0038] Figure 1 This is a typical schematic diagram of the LCC compensation topology;

[0039] Figure 2 The maximum and minimum ratios of the actual output voltage to the theoretical value vary with Qin, QO and LPr. (a) L Pr =3 and (b) L Pr =12, the maximum ratio varies with Qin and LPr; (c) Q O =6, the maximum ratio increases with Q in and L Pr Change. (a) L Pr =3 and (b) L Pr =12, the minimum ratio increases with Q in and L Pr Change; (c) Q O =6, the minimum ratio increases with Q in and L Pr change.;

[0040] Figure 3 It is a schematic diagram of the process of the present invention;

[0041] Figure 4 This is a schematic diagram of the relationship between the alignment position transmission efficiency and the coupler characteristics in Example 1;

[0042] Figure 5 Schematic diagram of the trade-off between compensation and coupling coil parameter deviation tolerance and alignment condition transfer efficiency. DETAILED DESCRIPTION

[0043] 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.

[0044] The present invention focuses on the design of compensation and coupling related parameters of wireless power transmission systems. The parameter deviation of passive components in the compensation link is inevitable and unpredictable. The resonance loss caused by parameter drift may lead to the deterioration of the stability, reliability, safety and transmission efficiency of the WPT system. The existing design methods do not fully consider the impact of compensation parameter deviations. Some design methods assume that compensation errors do not occur at the same time, which is inconsistent with actual working conditions.

[0045] The present invention comprehensively considers the possibility of deviation of compensation inductance and capacitance parameters. Commercial capacitors have several accuracy levels, such as ±10%, ±5%, etc., and even very small errors may lead to larger output characteristic deviations. Therefore, considering the aging effect, the deviation range of the compensation capacitor is set to ±10%. Compared with capacitors, the errors of compensation inductance and coil self-inductance are smaller. This is because they have no aging problems, and the use of molds can reduce manufacturing errors. The main reason for inductance deviation is misalignment, so the deviation range of compensation inductance and coil self-inductance is set to ±5%. The mutual inductance of the designed coupler is very sensitive to offset, and the variation range of mutual inductance is also set to ±10%.

[0046] The present invention takes the LCC-S topology as an example to illustrate the influence of compensation and coupling related parameter deviations on the system output voltage, power factor, transmission efficiency and resonant capacitor voltage.

[0047] The equivalent circuit diagram of the wireless power transmission system considering compensation and coupling related parameters is shown below:

[0048] See also Figure 1 , in the figure, U P is the root mean square (RMS) value of the primary inverter output voltage, and U S is the RMS value of the secondary rectifier input voltage. in and I P (I S ) is the RMS value of the primary inverter output current and the primary (secondary) coil current. r and C r They are the primary series compensation inductor and primary parallel compensation capacitor respectively. P (C S ) is the primary (secondary) series compensation capacitor, L P (L S ) is the self-inductance of the primary (secondary) coil. M is the mutual inductance, and R E Represents the equivalent load resistance.

[0049] When the compensation parameters satisfy the following formula,

[0050]

[0051] Where ω is the operating frequency, the output voltage can be expressed as:

[0052]

[0053] Since inductors and capacitors are not ideal devices in actual systems, there will be some losses when current flows through them. The quality factor Q is an important indicator of inductance, which is defined as the ratio of reactive power to active power.

[0054]

[0055] Where L is the inductance, I L is the inductor current, P L is the total loss, including the copper loss of the coil and the iron loss of the core.

[0056] The loss of the compensation capacitor accounts for a large proportion of the total system loss, so it needs to be taken into account in the theoretical analysis. The loss of the capacitor can be calculated by the dissipation factor, usually expressed as tanδ and can be found in the device manual.

[0057]

[0058] Among them, C, I C and P L They are the capacitance, current and loss of the capacitor respectively.

[0059] The transmission efficiency of the ideal LCC-S compensated WPT system can then be calculated:

[0060]

[0061] Where P Lr ,、P LP , P LS , P Cr , P CP , and P CS There are three inductor components (i.e. L r , L P and L S ) and three compensation capacitors (i.e., C r , C P and C S ) loss. Q r and Q P (Q S ) is the primary compensation inductance and the quality factor of the primary (secondary) coil. Pr YesL P The ratio of Q to Lr. in and Q O They are defined as the inverter quality factor and load quality factor respectively, which can be obtained by the following formula

[0062]

[0063] The present invention analyzes the influence of parameter drift on a WPT system with constant output power, and then finds out the dominant factors affecting the deviation tolerance of its compensation and coupling related parameters.

[0064] k m , k Lr , k LP , k LS , k Cr , k CP and k CS Defined as the ratio of the actual value to the ideal value of the corresponding component.

[0065] M=k m M0 (7)

[0066]

[0067]

[0068] The subscript 0 represents an ideal value, and the ideal value of the compensation device satisfies the resonance condition of formula (1).

[0069] The output voltage change ratio of the LCC-S compensated WPT system with parameter drift can be derived

[0070]

[0071] in,

[0072]

[0073] It is the ratio of the rated equivalent load resistance to the actual load resistance under the constant output power state.

[0074]

[0075] It can be obtained by solving,

[0076]

[0077] By solving (13), we obtain two solutions.

[0078]

[0079] in,

[0080]

[0081]

[0082] It can be seen from formula (13) that when d>0, there are two load resistors that make the system output the same rated power. According to the circuit law, the larger the load resistance, the higher the transmission efficiency of the system. Set to In practical application scenarios, this can be achieved through a secondary DC-DC converter.

[0083] When d≤0, the constant power output cannot be maintained due to parameter changes, and the output power will decrease. The DC-DC with PI closed-loop control controls the output power to the maximum power at that time, and its value can be derived from the following formula:

[0084]

[0085] Then k RE It can be derived as follows.

[0086]

[0087] In summary, when the output power is constant, parameter changes cause the equivalent load resistance to change, and the rate of change can be expressed as follows.

[0088]

[0089] It can be seen from (10) that the output voltage of the WPT system considering parameter deviation is (Q in , Q O , L Pr , k m , k Lr , k LP , k LS , k Cr , k CP , k CS ), which is a 10-dimensional variable problem, making the theoretical analysis complicated. Compensation and coupling related parameters (k m , k Lr , k LP , k LS , k Cr , k CP , k CS ) deviations are unpredictable and inevitable, which may significantly reduce the transmission efficiency, stability and robustness of the WPT system. (Q in , Q O , L Pr ), which is determined by the operating frequency, rated coil parameters, compensation inductance and load resistance, and can be optimized in the design stage to improve the tolerance of parameter changes.

[0090] Therefore, the next major task is to analyze (Q in , Q O, L Pr ) on the sensitivity of system compensation and coupling related parameter deviations, and then determine the design constraints of a system with high compensation and coupling related parameter change rate tolerance.

[0091] Considering the deviation of compensation and coupling related parameters, the variation range of mutual inductance is also set to ±10%. That is, 0.9≤k m , k Cr , k CP , k CS ≤1.1,0.95≤k Lr , k LP , k LS ≤1.05.

[0092] According to the previous analysis, it is almost impossible to intuitively judge the impact of each variable on the output voltage due to the numerous influencing factors. Considering the inevitable and unpredictable characteristics of parameter deviation, the worst case, that is, the extreme value of the output voltage, should be used to quantitatively measure the impact of compensation and coupling related parameter deviations on the output voltage. However, since this is a 10-D problem, it is also very difficult to obtain an accurate analytical solution for the extreme value. Numerical methods are an alternative. Q in and Q O Sweep from 0.2 to 10, L Pr Sweep from 1 to 16. Use global search algorithm to calculate each combination (Q in , Q O , L Pr )'s maximum and minimum k US It should be noted that although the inverter quality factor, load quality factor, L Pr will vary with the deviation of the parameters, but (Q in , Q O , L Pr ) is calculated using ideal system parameters, i.e. the WPT system remains unchanged after design. Calculate the maximum and minimum k US , k US-max , and k US-min , as shown in Figure 2.

[0093] from Figure 2 (c) and (f) show that L Pr The effect of is monotonic, so only L Pr =3 and L Pr = 12 is enough to illustrate the picture in and Q O K US-max and k US-min In addition, Q in The increase and Q O and L PrThe reduction of k US-max The rate of change of Figure 2 (d) and (e) show that k US-min Basically unchanged, except for Q in and Q O There is a small raised area when they are very small. This is because (Qi n , Q O , L Pr ) combination to obtain the minimum output voltage, d is less than 0, that is, the output power cannot be maintained at the rated value. Figure 2 (d) and (e) The location of the raised area and Figure 2 (f) k US-min It can be seen from the changing trend that to obtain a higher minimum output voltage, a smaller Q is required. in , Q O and L Pr .

[0094] Similarly, similar methods can be used to analyze the impact of these three parameters on system transmission efficiency, power factor and compensation capacitor voltage, so as to find the appropriate Q in , Q O and L Pr The combined value guides the design of coupling coil parameters for high-tolerance wireless power transfer systems.

[0095] In order to achieve multi-objective optimization of the coupler, the relationship between parameter variation tolerance and transmission efficiency was analyzed, and the tolerance of compensation and coupling coil parameter variation was proposed to be expressed by a comprehensive index χ, which is defined as:

[0096]

[0097] Among them, α, β, and γ are weight coefficients, which are 0.5, 0.1, and 1 respectively. Since the variables in formula (20) are dimensionless, the definition method of the comprehensive index is feasible.

[0098] See also Figure 3 , the specific design flow is as follows:

[0099] By analyzing the deviation characteristics of compensation and coupling coil parameters, the appropriate Q in , Q O and L Pr Parameters, which are independent of specific application conditions and have a certain degree of universality, can guide the design of a WPT system with high parameter tolerance. The design process is shown in the figure below.

[0100] The first step is to analyze the deviation characteristics and give Q in , Q O and L Pr Initial values ​​of parameters;

[0101] The second step is to determine the input voltage, output power and other boundary conditions for specific application conditions. in , Q O and L Pr The initial values ​​of the parameters are used to obtain the compensation and coupling coil design parameters, including L P The upper limit value, L S The upper limit of , and the lower limit of M.

[0102] The third step is to select the coil parameters that meet the constraints through ANSYS simulation and select the coil parameters that meet L P The upper limit value, L S The upper limit value of and the lower limit value of M are brought into the efficiency constraint formula to determine whether the efficiency constraint is met, such as not less than 90%.

[0103] In the fourth step, the coil parameters designed after the third step are compared, and the coupling coil design result with the smallest comprehensive index χ for tolerance is selected as the output.

[0104] At this point, the design parameters of the coupling coil are obtained, and the compensation link is still designed according to the resonance conditions.

[0105] In order to further illustrate the present application, the following specific embodiments are provided:

[0106] Embodiment 1:

[0107] This section takes the design case of high CCP deviation tolerance of 22kW WPT of electric bus as an example, and optimizes the parameter variation tolerance of WPT system by designing system parameters (Qin, QO, LPr). Among the 6 parameters (Qin, QO, LPr) determined, RE is determined by the load, and Lr is determined by mutual inductance and voltage gain. Therefore, the key to design (Qin, QO, LPr) is to optimize the parameters of the coupler, namely LP, LS, and M.

[0108] The traditional design method only optimizes the transmission efficiency, power density and misalignment tolerance characteristics of the coupler. However, CCP variation tolerance is also a very important feature, because according to the previous analysis, the WPT system designed without considering parameter drift performs poorly in terms of transfer efficiency, robustness and safety. Since there are many factors that affect the performance of the coupling coil, such as the structure and size of the coil and the core, the number of turns of the coil, etc., it is very likely to achieve a better trade-off between transmission efficiency, parameter variation tolerance and power density through the reasonable design of the coupling coil. On this basis, a design example of a 22kW WPT charger with multi-objective optimization is given.

[0109] Figure 4The relationship between the transmission efficiency and the reduction in mutual inductance, the size of the secondary coil, and the weight of the receiving coil is given. The offset characteristic is expressed by the reduction in mutual inductance. The weight of the receiving coil is the sum of the weight of the secondary coil and the core, and the weight of the packaging is not considered. In practical applications, the size and weight of the receiving coil installed on the vehicle are usually more concerned, so the relationship between the transmission efficiency and the size and weight of the transmitter is not studied.

[0110] from Figure 4 It can be seen that near the peak point, a small increase in efficiency comes at the expense of a significant increase in the mutual inductance drop rate and the size and weight of the receiver. For example, the transfer efficiency of this design can reach up to 98.06%, but the length of the primary and secondary coils are both 800mm, the maximum mutual inductance drop rate is 30.41%, and the secondary weight is 24.2kg. In order to achieve a good balance between the transfer efficiency, misalignment tolerance, and power density of the system, the cost function is a good choice, but due to the inconsistent sizes of these variables, the coefficients of each variable are difficult to determine. Alternatively, this paper manually selects the optimal solution. Taking the mutual inductance drop rate and the receiver weight as design constraints, which are less than 20% and 20kg respectively, as shown in Figure 4 In the simulation of this paper, the maximum length of the receiver coil less than 20kg is 700mm, so the size is no longer restricted separately.

[0111] In order to achieve multi-objective optimization of the coupler, the relationship between parameter variation tolerance and transfer efficiency is analyzed, such as Figure 5 The tolerance to changes in compensation and coupling coil parameters is represented by a comprehensive index χ, as shown in formula (20).

[0112] Figure 5 The χ in is calculated using the simulated drop rates of the mutual and self inductances of the coupler, while the deviations of the series compensation inductance and capacitance are ±5% and ±10%, respectively. Figure 5 It shows that the variation tolerance of compensation and coupling related parameters and the transmission efficiency cannot reach extreme values ​​at the same time. The highest transmission efficiency is 97.51%, but the parameter variation tolerance index of this candidate design is only 0.988. In general, except at the peak, there are multiple coupler coils that can achieve the same transmission efficiency, but their error tolerances are very different. Table. I shows the parameter characteristics of several groups of coupling coils.

[0113] Table I: Comparison of parameters of simulated coupled coils

[0114]

[0115]

[0116] According to Table.I, the transmission efficiency of the first and fifth groups is almost the same, but their parameter variation tolerance is very different, especially in the maximum rise ratio of the output voltage kUS-max, the voltage of the primary parallel capacitor kUCr-max and the secondary series capacitor kUCS-max. The same conclusion can be drawn from the second and fourth groups. In order to achieve a good balance between CCP variation tolerance and transmission efficiency, the second group of particles was selected as the optimization result. The efficiency of this candidate is only 0.08% lower than the highest one, but the parameter variation tolerance index is 0.108 lower and 10.9% higher. In addition, the length of the secondary coil is only 600 mm and the weight of the receiver is 18.2 kg, which also shows an improvement in power density (0.45 kW / mm2, 1.21 kW / kg) compared with the third particle with the highest efficiency (700 mm, 19.5 kg, 0.34 kW / mm2, 1.13 kW / kg).

[0117] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A WPT system coupling coil and compensation parameter design method, characterized in that: The following steps are involved: By analyzing the deviation characteristics, the inverter quality factor Q is given in The initial value is denoted as Q in-s , Load quality factor Q O Q O-s , the self-inductance of the primary coil L P The primary series compensation inductor L r The ratio L Pr The initial value is denoted as L Pr-s ; According to the boundary conditions required by the working conditions and the determined Q in , Q O , L Pr The initial value of is used to obtain the design parameters of the compensation and coupling coils that meet the constraints; Through simulation, the design parameters of compensation and coupling coils that meet the constraints are selected in groups; Substitute the selected compensation and coupling coil design parameters into the efficiency constraint formula to determine whether they meet the set constraint threshold; if they meet, they are retained; if not, they are discarded; Obtain the tolerance comprehensive index of the compensation and coupling coil design parameters that reach the set constraint threshold, and select the compensation and coupling coil design parameters of the constraint threshold with the smallest tolerance comprehensive index as output The efficiency constraint formula is: Among them, I S is the RMS value of the secondary coil current, R E is the equivalent load resistance; P Lr ,、P LP , P LS , P Cr , P CP , and P CS There are three inductance components L r , L P and L S and three compensation capacitors C r , C P and C S The loss of Q r , Q P , Q S is the quality factor of the primary compensation inductor, primary coil, and secondary coil; L Pr YesL P and L r ratio; tanδ is the dissipation factor of the capacitor; Q in and Q O They are defined as the inverter quality factor and the load quality factor respectively, and are obtained by the following formula: Where, ω is the operating frequency, M is the mutual inductance; The tolerance composite index is defined as: Among them, α, β, γ are weight coefficients; k US-max and k US-min It is k US The maximum and minimum values ​​of the system input power factor; λmin is the minimum value of the system input power factor; Δη max k is the maximum value of the system transmission power change; US is the output voltage change ratio; Among them, k US It is expressed as: Where U s is the actual value of the effective value of the secondary rectifier input voltage; j is the imaginary unit; α is expressed as: k RE It is the ratio of the rated equivalent load resistance to the actual load resistance under the constant output power state; K UCr-max , K UCp-max and K UCs-max They are respectively expressed as the maximum value of the voltage rise ratio of the primary parallel compensation capacitor, the primary series compensation capacitor and the secondary series compensation capacitor.

2. A WPT system coupling coil and compensation parameter design method according to claim 1, characterized in that: The boundary conditions required by the working condition include at least: input voltage U P , output power P O .

3. A WPT system coupling coil and compensation parameter design method according to claim 1, characterized in that: The compensation and coupling coil design parameters include: the self-inductance L of the primary coil P The upper limit value of the secondary coil self-inductance L S The upper limit value of , the lower limit value of mutual inductance M.

4. A WPT system coupling coil and compensation parameter design method according to claim 1, characterized in that: in, The simulation is performed by ANSYS software.

5. A WPT system coupling coil and compensation parameter design method according to claim 1, characterized in that: The constraint threshold is 90%.

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