Bilateral capacitive array wpt system and adaptive critical coupling coefficient adjustment method

Abstract

This invention provides a two-sided capacitor array WPT system and an adaptive critical coupling coefficient adjustment method. The primary circuit includes a DC power supply, a high-frequency inverter circuit, a primary-side adjustable capacitor array, and a transmitting coil. The secondary circuit includes a receiving coil, a secondary-side adjustable capacitor array, a rectifier module, and a load. The equivalent capacitance of the primary-side adjustable capacitor array and the transmitting coil form a primary-side resonant circuit, and the equivalent capacitance of the secondary-side adjustable capacitor array and the receiving coil form a secondary-side resonant circuit. The primary circuit also includes a current detection circuit for detecting the primary-side resonant current and a drive module for controlling the output voltage and current of the high-frequency inverter circuit to maintain in-phase operation based on the primary-side resonant current. By using a two-sided capacitor array to adjust the natural resonant frequency, the critical coupling coefficient of the system can be adjusted, thus widening the transmission distance range and effectively realizing long-distance constant power and constant efficiency wireless power transmission. The circuit topology is simple and easy to implement.

Description

Technical Field

[0001] This invention relates to wireless power transfer technology, specifically to a bilateral capacitor array (WPT) system and an adaptive critical coupling coefficient adjustment method. Background Technology

[0002] Wireless power transfer (WPT) technology uses media such as magnetic fields, electric fields, lasers, and microwaves to achieve non-electrical contact transmission of electrical energy. This technology effectively solves the problems of limited equipment flexibility and safety hazards caused by traditional wired power supply methods. Currently, it is used in electric vehicles, consumer electronics, and home appliances.

[0003] Currently, most research in the field of WPT (Wireless Power Transfer) systems employs resonant wireless power transfer technology, which is primarily based on the principles of magnetic resonance and electric field resonance. Within a certain transmission distance, this system can maintain high transmission efficiency and output power. However, the system is sensitive to transmission distance and the relative position of the coils. Any deviation in coil position will significantly alter transmission efficiency and output power. To address this issue, researchers both domestically and internationally have largely employed two strategies to optimize the impact of coil misalignment: frequency control and impedance matching.

[0004] Reference: Zhang Bo, Shu Xujian, Wu Lihao, et al. Problems and countermeasures to be solved in wireless power transfer technology [J]. Automation of Electric Power Systems. 2019, 43(18): 1-12. By theoretically modeling series-series (SS) and parallel-parallel (PP) WPT systems, a maximum power frequency tracking method is proposed. This method determines the optimal operating frequency by applying a small perturbation to the frequency and measuring the change in output frequency.

[0005] Reference: Xue Ming, Yang Qingxin, Zhang Pengcheng, et al. Research status and key issues of wireless power transfer technology [J]. Journal of Electrical Engineering. 2021, 36(08): 1547-1568. A strategy for tracking the real-time natural resonant frequency is proposed. By detecting the phase difference between the inverter output voltage on the primary side and the current of the transmitting coil, the operating frequency is adjusted in real time so that the phase difference between the inverter output voltage and the current of the transmitting coil is always in the zero phase angle (ZPA) mode.

[0006] References: Li Yang, Shi Shaobo, Liu Xueli, et al. A review of magnetic field-coupled wireless power transfer coupling mechanisms [J]. Journal of Electrical Engineering. 2021, 36(S2): 389-403. Based on the LCC-S-based WPT system, the analysis shows that the cross-coupling between multiple coils in the load causes a shift in the system's operating frequency from the free resonant frequency, resulting in a significant reduction in transmission efficiency. Based on this, a capacitor array is added to the primary side, and a radial basis function neural network is used to select suitable compensation capacitors. Experimental results show that the system can improve the transmission efficiency from the lowest point of 34% to 78%. The above references all optimize the changed power and efficiency, but overall, the system's transmission efficiency and output power still exhibit significant variations.

[0007] In 2017, Assawaworrarit et al. first applied parity-time (PT) symmetry theory to WPT systems. This research utilized operational amplifier circuits to construct a nonlinear saturated gain-negative resistance system and leveraged the frequency-selective characteristics of the operational amplifier's self-oscillating system. Specifically, the secondary side's reflection impedance was considered a frequency-selective network, dependent only on the frequency of the output voltage and independent of its amplitude and phase; more importantly, its amplitude was unaffected by the transmission distance. Therefore, the system could achieve constant output power and constant transmission frequency. However, due to the low output voltage amplitude of the operational amplifier, the system's output power was relatively low, only 19.7mW. Nevertheless, its ability to achieve constant output power and constant transmission efficiency subsequently inspired numerous researchers to study the application of PT symmetry in WPT. In subsequent research, due to the low output power of the operational amplifier, the use of inverters to output in-phase voltage and current was proposed to construct a nonlinear gain, essentially building a forced response system.

[0008] Reference: Wang Youqing, Zhang Haiyan, Qi Liang. Research on key technologies of magnetically coupled resonant wireless power transfer [J]. Shanghai Electric Technology. 2019, 12(01): 1-6. The PT symmetry theory is applied to the dual-coupled (magnetic field coupling, electric field coupling) WPT system. The coupled-mode theory (CMT) is used to derive the system theoretically. The theory shows that the system can achieve constant output power and constant transmission efficiency over a longer distance than the single-coupled system, but its overall output transmission efficiency is lower. Summary of the Invention

[0009] Based on the above requirements, the primary objective of this invention is to propose a bilateral capacitor array WPT system, which reduces the critical coupling coefficient of the system by introducing only two sets of adjustable capacitor arrays, thereby achieving long-distance constant power and constant efficiency wireless power transmission.

[0010] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0011] A double-sided capacitor array WPT system includes a primary-side circuit and a secondary-side circuit. The key features are: the primary-side circuit is equipped with a DC power supply, a high-frequency inverter circuit, a primary-side adjustable capacitor array, and a transmitting coil; the secondary-side circuit is equipped with a receiving coil, a secondary-side adjustable capacitor array, a rectifier module, and an electrical load.

[0012] The equivalent capacitance of the primary-side adjustable capacitor array and the transmitting coil form a primary-side resonant circuit, and the equivalent capacitance of the secondary-side adjustable capacitor array and the receiving coil form a secondary-side resonant circuit. The primary-side circuit also includes a current detection circuit for detecting the primary-side resonant current and a drive module for controlling the output voltage and output current of the high-frequency inverter circuit to maintain them in phase based on the primary-side resonant current. The secondary-side adjustable capacitor array and the primary-side adjustable capacitor array are used to change the corresponding equivalent capacitance value according to changes in the load, so that the system maintains a parity-time symmetric state.

[0013] Optionally, the high-frequency inverter circuit adopts a full-bridge inverter circuit composed of switching transistors Q1, Q2, Q3 and Q4.

[0014] Optionally, the current detection circuit includes a current sensor and a zero-crossing comparator.

[0015] Optionally, the natural resonant angular frequency of the primary resonant circuit is set to ω. p The natural resonant angular frequency of the secondary resonant circuit is ω. s If the operating angular frequency of the resonant current output by the high-frequency inverter circuit is ω, then the system operates according to ω. p =ω s The constraint relationship ≠ω controls the operating state of the primary-side adjustable capacitor array, the secondary-side adjustable capacitor array, and the high-frequency inverter circuit, so that the system maintains a parity-time symmetric state.

[0016] Optionally, both the primary-side adjustable capacitor array and the secondary-side adjustable capacitor array are composed of multiple capacitor elements connected in parallel, with each capacitor element connected to a circuit breaker.

[0017] Based on the above system, this invention also proposes an adaptive critical coupling coefficient adjustment method for a bilateral capacitor array (WPT) system, which mainly includes the following steps:

[0018] S1: The primary resonant current is acquired through the current detection circuit;

[0019] S2: Determine the deviation of the current input impedance of the system from the input impedance under parity-time symmetry based on the current primary resonant current;

[0020] S3: When the deviation value obtained in step S2 is greater than the preset threshold, the system critical coupling coefficient is changed by adjusting the equivalent capacitance values ​​of the primary adjustable capacitor array and the secondary adjustable capacitor array, so that the current system coupling coefficient is greater than or equal to the system critical coupling coefficient.

[0021] S4: Adjust the operating angular frequency of the system according to the natural resonant angular frequencies of the primary and secondary resonant circuits after adjustment, so that the system can be restored to a parity-time symmetric state, and return to step S1 for repeated execution.

[0022] Optionally, in step S2, the current input impedance Z1' of the system is determined according to... Calculate, where V p i' is the fundamental component of the output voltage of the high-frequency inverter circuit. p The current transmitting coil current; the input impedance Z1 in the parity-time symmetrical state is according to... Calculate, where L p R is the self-inductance of the transmitting coil. p L is the parasitic resistance value of the transmitting coil. s R is the self-inductance value of the receiving coil. s R is the parasitic resistance value of the receiving coil. eq The equivalent resistance of the electrical load is given by the deviation value Δ = |Z1 - Z'1|.

[0023] Optionally, in step S3, when the deviation value obtained in step S2 is greater than a preset threshold, the current coupling coefficient of the system is first measured using an LCR bridge, and this value is used as the critical coupling coefficient k of the system. a Then according to The constraint relationship is used to determine the equivalent capacitance value C of the secondary adjustable capacitor array. s L s R is the self-inductance value of the receiving coil. s R is the parasitic resistance value of the receiving coil. L The resistance value of the electrical load is used, and finally the equivalent capacitance value of the primary-side adjustable capacitor array is adjusted according to the constraint relationship that the natural resonant angular frequency of the primary-side resonant circuit is equal to the natural resonant angular frequency of the secondary-side resonant circuit.

[0024] Optionally, according to Determine the system's operating angular frequency, where ω0 is the natural resonant angular frequency of the primary and secondary resonant circuits, and k is the current coupling coefficient of the system. This indicates the quality factor of the secondary circuit.

[0025] The effects of this invention are:

[0026] This invention proposes an adaptive critical coupling coefficient adjustment method for a bilateral capacitor array WPT system. By using a bilateral capacitor array to adjust the natural resonant frequency, the critical coupling coefficient of the system can be adjusted, thus widening the transmission distance range and effectively realizing long-distance constant power and constant efficiency wireless power transmission. The circuit topology is simple and easy to implement. Attached Figure Description

[0027] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0028] Figure 1 This is a system architecture diagram in a specific embodiment of the present invention;

[0029] Figure 2 for Figure 1 The equivalent circuit diagram;

[0030] Figure 3 This is a control flowchart for adaptive critical coupling coefficient adjustment in a specific embodiment of the present invention;

[0031] Figure 4 This is a graph showing the relationship between the operating frequency and the coupling coefficient.

[0032] Figure 5 The waveform of the input signal before adjustment of the adjustable capacitor array is shown.

[0033] Figure 6 This is a waveform diagram of the input signal after adjustment by the adjustable capacitor array;

[0034] Figure 7 The waveform of the output signal before adjustment of the adjustable capacitor array is shown.

[0035] Figure 8 This is a waveform diagram of the output signal after adjustment by the adjustable capacitor array;

[0036] Figure 9 A comparison diagram of the transmitting coil current before and after adjustment of the adjustable capacitor array;

[0037] Figure 10 The graph shows the changes in transmission efficiency and coupling coefficient before and after adjustment of the adjustable capacitor array.

[0038] Figure 11 The graph shows the changes in output power and coupling coefficient before and after adjustment of the adjustable capacitor array. Detailed Implementation

[0039] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0040] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0041] like Figure 1 As shown, this embodiment provides a two-sided capacitor array WPT system, including a primary-side circuit and a secondary-side circuit. The primary-side circuit includes a DC power supply, a high-frequency inverter circuit, a primary-side adjustable capacitor array, and a transmitting coil. The secondary-side circuit includes a receiving coil, a secondary-side adjustable capacitor array, a rectifier module, and an electrical load. The equivalent capacitance of the primary-side adjustable capacitor array and the transmitting coil form a primary-side resonant circuit, and the equivalent capacitance of the secondary-side adjustable capacitor array and the receiving coil form a secondary-side resonant circuit. The secondary-side adjustable capacitor array and the primary-side adjustable capacitor array are used to change the corresponding equivalent capacitance value according to the change of load, so that the system maintains a parity-time symmetric state.

[0042] from Figure 1 It can be seen that L p L s R p R s These represent the self-inductance and parasitic resistance of the transmitting and receiving coils, respectively; M is the mutual inductance between the transmitting and receiving coils; Q1, Q2, Q3, and Q4 are the four switching transistors of the high-frequency inverter circuit, using a full-bridge inverter circuit composed of transistors Q1, Q2, Q3, and Q4; U d D1, D2, D3, and D4 are the input voltage of the DC power supply; D1, D2, D3, and D4 are the four diodes of the rectifier module; R L i is the load resistance; p i s These are the resonant currents corresponding to the transmitting coil and the receiving coil, respectively.

[0043] To achieve negative resistance in the primary circuit, a current detection circuit for detecting the primary resonant current and a drive module for controlling the output voltage and output current of the high-frequency inverter circuit to maintain in-phase operation based on the primary resonant current are also included in the primary circuit. Figure 2 As can be seen, the current detection circuit includes a current sensor and a zero-crossing comparator. In this embodiment, a high-frequency inverter circuit (composed of four MOSFETs Q1, Q2, Q3, and Q4 connected together) is used to detect the DC power supply U. d The inverter produces a high-frequency voltage, which is then used to obtain the output current signal i via a current sensor. p The zero-crossing comparator then feeds the zero-crossing signal back to the drive module of the high-frequency inverter, generating a corresponding drive signal. Through this process, the output voltage and output current of the full-bridge inverter can be kept in phase, thus achieving an equivalent nonlinear saturation gain, i.e., negative resistance -R. N .

[0044] To simplify the analysis, we can Figure 1 The circuit shown is simplified as follows Figure 2 The structure shown has a natural resonant angular frequency of ω for the primary resonant circuit. p The natural resonant angular frequency of the secondary resonant circuit is ω. s The operating angular frequency of the resonant current output by the high-frequency inverter circuit is ω. To maintain the system in a parity-time symmetric state, the system must operate according to ω. p =ω s The constraint relationship ≠ω is controlled, and the specific analysis process is as follows:

[0045] According to Kirchhoff's voltage law Figure 2 The circuit shown can be represented as:

[0046]

[0047] The above equation can be simplified to:

[0048]

[0049] In the formula, k is the coupling coefficient, ω0 is the natural resonant frequency, and the above formula... For a real solution, the following must be satisfied:

[0050]

[0051] Then we have:

[0052]

[0053] Separating the real and imaginary parts in equation (4), we get:

[0054]

[0055] If the system is in a PT-symmetric state, ω≠ω0 must be satisfied, therefore:

[0056]

[0057] Furthermore, from equation (5), we can obtain:

[0058]

[0059] in It is actually the quality factor of the secondary side.

[0060] If ω 1,2 If it is a real number, then it must satisfy:

[0061]

[0062] In actual operation, the quality factor of the coils in the WPT system is very high. Therefore, equation (8) automatically satisfies the inequality condition.

[0063] Will

[0064] k a This is called the critical coupling coefficient, where k ≥ k a The region is called a strongly coupled region.

[0065] Equation (2) can be transformed into:

[0066]

[0067] From equation (10), we can obtain:

[0068]

[0069] From equation (11), we can obtain the expressions for the output power P and transmission efficiency η of the WPT system in PT symmetry state:

[0070]

[0071]

[0072] In the formula, V P This represents the fundamental component of the inverter's output voltage.

[0073] From equations (12) and (13), it can be seen that the WPT system in the PT symmetric state has a transmission efficiency that is only related to the load resistance, the self-inductance L of the transmitting coil and the receiving coil. s L p Parasitic resistance R s R p It is related to, but independent of, the coupling coefficient k. Furthermore, the output power is only related to, the load resistance, and the self-inductance L of the transmitting and receiving coils. s L p Parasitic resistance R s R p ; and V p It is related to the coupling coefficient k.

[0074] Equation (9) can be expanded as follows:

[0075]

[0076] As can be seen from equation (14), due to the self-inductance of the regulating coil (L) s This will affect the parasitic resistance, and there will be coupling between parameters. Therefore, the parasitic resistance can be affected by changing the secondary-side compensation capacitor C. s To achieve the critical coupling coefficient k aThe adjustment is necessary, but considering the PT symmetry state, when the coil parameters remain unchanged, the resonant frequencies of the primary and secondary sides must be consistent. Therefore, if the critical coupling coefficient is to be adjusted by changing the secondary resonant capacitance, the capacitances C of the primary and secondary sides must be adjusted accordingly. p C s The changes must be simultaneous, and the natural resonant frequencies of the primary and secondary sides must be equal. In practice, both the primary-side and secondary-side adjustable capacitor arrays are composed of multiple capacitor elements connected in parallel. Each capacitor element is connected to a circuit breaker, and different equivalent capacitance values ​​are achieved by controlling the switch's closed state. To achieve a wide range of adjustment for the capacitor array, the resistance values ​​of each adjusting capacitor should be different.

[0077] The impact of the equivalent capacitance of the adjustable capacitor array on output power and transmission efficiency is analyzed below:

[0078] Change the equivalent capacitance C of the switch-adjustable capacitor array p C s The essence is to adjust the natural resonant frequency between the transmitting and receiving sides. According to Kirchhoff's voltage law, the secondary impedance is equivalent to the primary impedance and denoted as Z. 21 Then we have:

[0079]

[0080] Then from the negative resistance -R N Looking at it, its input impedance Z1 is:

[0081]

[0082] Let ω = ω 1，2 Substituting into equation (16), we get:

[0083]

[0084] Therefore, when the WPT system is in a PT-symmetric state, its input impedance Z1 is independent of the natural resonant angular frequency ω0, and is only related to the self-inductance L corresponding to the transmitting and receiving coils. p ,L s and parasitic resistance R p R s And related to the load resistance Req. If the input impedance remains constant, the current i in the primary side transmitting coil of Z1 is... p constant.

[0085] According to equation (11), if the current in the transmitting coil remains constant, then the current i in the receiving coil... p If it remains unchanged, then the current i in the receiving coil s Since it remains unchanged, the output power P and transmission efficiency η will also remain unchanged. In summary, by changing the equivalent capacitance C of the adjustable capacitor array...p C s By adjusting the natural resonant frequencies of the transmitting and receiving sides, and consequently adjusting the operating frequency of the system, the transmission efficiency η and output power P of the system remain unaffected when the system re-achieves the PT symmetry state.

[0086] Based on the conclusions drawn from the previous analysis, when k < k a At this point, the system is in the weakly coupled region and is no longer in a PT-symmetric state. In this state, the system's transmission efficiency η and output power P are easily affected by the coupling coefficient k. However, this can be mitigated by changing the adjustable capacitor array C. P C s The equivalent capacitance value is used to reduce the critical coupling coefficient k. a Substituting the adjusted capacitance value into equation (7), we obtain the corresponding operating angular frequency ω'. 1，2 This brings the system back to a PT-symmetric state, enabling the system to achieve constant output power and constant transmission power over a longer transmission distance. Therefore, to detect whether the WPT system is in a strongly coupled region, this embodiment also proposes an adaptive critical coupling coefficient adjustment method for a bilateral capacitor array WPT system, which only requires measuring the current i in the primary side transmitting coil. p According to equation (17), if the entire WPT system is in a PT-symmetric state, that is, in a strongly coupled region, the input impedance of the system is Z1, and the measured transmitting coil current i' is used. p Calculate the input impedance Z'1 at this time:

[0087]

[0088] Assumption:

[0089] Δ=|Z1-Z'1| (19)

[0090] When Δ≤ε, the system is considered to be in the PT state, i.e., in the strongly coupled region, and ε is the error magnitude. When Δ>ε, the system is considered not to be in the PT state, i.e., in the weakly coupled region, and ε is the error magnitude.

[0091] Therefore, as Figure 3 As shown, in this embodiment, the adaptive critical coupling coefficient adjustment method of the bilateral capacitor array WPT system specifically includes the following steps:

[0092] S1: The primary resonant current is acquired through a current detection circuit;

[0093] S2: Determine the deviation of the current input impedance of the system from the input impedance under parity-time symmetry based on the current primary resonant current;

[0094] S3: When the deviation value obtained in step S2 is greater than the preset threshold, the system critical coupling coefficient is changed by adjusting the equivalent capacitance values ​​of the primary adjustable capacitor array and the secondary adjustable capacitor array, so that the current system coupling coefficient is greater than or equal to the system critical coupling coefficient.

[0095] S4: Adjust the operating angular frequency of the system according to the natural resonant angular frequencies of the primary and secondary resonant circuits after adjustment, so that the system can be restored to a parity-time symmetric state, and return to step S1 for repeated execution.

[0096] Specifically, in step S3, when the deviation value obtained in step S2 is greater than a preset threshold, the current coupling coefficient of the system is first measured using an LCR bridge, and this value is used as the critical coupling coefficient k of the system. a Then according to The constraint relationship is used to determine the equivalent capacitance value C of the secondary adjustable capacitor array. S Finally, the equivalent capacitance value of the primary-side adjustable capacitor array is adjusted according to the constraint that the natural resonant angular frequency of the primary-side resonant circuit is equal to the natural resonant angular frequency of the secondary-side resonant circuit.

[0097] After the natural resonant frequencies of the primary and secondary sides are adjusted by changing the resonant capacitance, then according to:

[0098] Determine the system's operating angular frequency.

[0099] To verify the correctness of the system and method proposed in this invention, a system was built in Simulink as follows: Figure 2 The simulation circuit is shown in Table 1. The specific simulation parameters are shown in Table 1. The parasitic resistances of the transmitting and receiving coils are empirical values ​​based on previous experimental data.

[0100] Table 1 Simulation Parameters

[0101]

[0102] Substituting the simulation parameters from Table 1 into equation (7), we can obtain the following: Figure 4 The graph shows the change in operating frequency as a function of coupling coefficient. From... Figure 4 It can be seen that when k < 0.15, the system is in a weakly coupled state, with an operating frequency f = f0. At this point, the system's transmission efficiency and transmission power are no longer stable. When k ≥ 0.15, the system is in a strongly coupled state, and the operating frequency exhibits a bifurcation phenomenon, with the operating frequency f = f0. 1,2 At this time, the system's transmission efficiency and transmission power remain stable.

[0103] To verify the conclusions, the experiment compared the input and output waveforms of the system before and after adjustment of the adjustable capacitor array, as well as the output power and transmission efficiency. The C value before adjustment...p C s =77.6nF, which corresponds to the natural resonant frequency f0 = 57.1kHz, and the critical coupling coefficient k a =0.15. Adjusted C' p ,C' s =77.6nF, which corresponds to the natural resonant frequency f0 = 95.4kHz, and the critical coupling coefficient k a =0.09, simulation results are as follows Figures 5-11 As shown.

[0104] from Figure 5 and Figure 6 It can be seen that after adjusting the adjustable capacitor array, the natural resonant frequency is adjusted, and there is no phase angle difference between the inverter output voltage and the transmitting coil current on the input side. This confirms that after adjusting the natural resonant frequency, as long as the system is in a PT symmetrical state, the inverter output voltage V at its input end will remain constant. in and transmitting coil current i s It is in ZPA state.

[0105] from Figure 7 , Figure 8 and Figure 9 It can be seen that after the adjustable capacitor array is adjusted, the natural resonant frequency of the system changes. However, after adjusting the operating frequency of the system according to the frequency obtained by equation (7), the system returns to the PT symmetric state, and its equivalent load voltage U L The amplitudes of the current in the transmitting coil and the receiving coil remain unchanged, and the only difference between them is in frequency. In summary, this verifies that after changing the natural resonant frequency, the current amplitudes in the transmitting coil, the equivalent load voltage, and the current amplitude in the receiving coil remain unchanged after adjusting the corresponding operating frequency by formula (7), and the only difference is in frequency.

[0106] from Figure 10 , Figure 11 It is evident that at k=0.15, if the natural resonant frequency is not adjusted, i.e., the adjustable capacitor array is not adjusted, the system will exhibit both efficiency and power jump points. Figure 11 It can be seen that before adjustment by the adjustable capacitor array, the critical coupling coefficient of the system is 0.15. When the transmission distance of the system is too long, k... <k a At this point, the system is no longer in a PT-symmetric state, and the transmission efficiency will decrease drastically. After adjusting the adjustable capacitor array, the critical coupling coefficient of the system can be reduced to 0.09, allowing it to maintain a transmission efficiency of 87.2% in the range of k = 0.09-0.15. Similarly, before adjusting the adjustable capacitor array, when the system transmission distance is too long, k... <k aThe output power will increase significantly at this time, a phenomenon caused by mode overlap. Sudden power jumps will cause a significant increase in output current, which can burn out the load in severe cases. After adjustment with an adjustable capacitor array, the critical coupling coefficient of the system can be reduced to 0.09, allowing it to maintain 300W output power within the range of k = 0.09-0.15.

[0107] In summary, the proposed WPT system with a bilateral capacitor array and an adaptive critical coupling coefficient adjustment method fully demonstrate that changes in the natural resonant frequency will not affect the output power and transmission efficiency of the WPT system under PT symmetry. By using a bilateral capacitor array to adjust the natural resonant frequency, the critical coupling coefficient can be adjusted, thus widening the transmission distance range. The circuit topology is simple and easy to implement.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and such transformations should be covered within the scope of the claims and specification of the present invention.

Claims

1. A double-sided capacitor array WPT system, comprising a primary-side circuit and a secondary-side circuit, characterized in that: The primary circuit includes a DC power supply, a high-frequency inverter circuit, a primary adjustable capacitor array, and a transmitting coil; the secondary circuit includes a receiving coil, a secondary adjustable capacitor array, a rectifier module, and an electrical load. The equivalent capacitance of the primary-side adjustable capacitor array and the transmitting coil form a primary-side resonant circuit, and the equivalent capacitance of the secondary-side adjustable capacitor array and the receiving coil form a secondary-side resonant circuit. The primary-side circuit is also provided with a current detection circuit for detecting the primary-side resonant current and a drive module for controlling the output voltage and output current of the high-frequency inverter circuit to keep them in phase according to the primary-side resonant current. The deviation of the current input impedance from the input impedance under parity-time symmetry is determined based on the current primary-side resonant current. When the deviation exceeds a preset threshold, the current coupling coefficient of the system is first measured using an LCR bridge and taken as the critical coupling coefficient of the system. Then according to The constraint relationship is used to determine the equivalent capacitance value of the secondary adjustable capacitor array. ,in The self-inductance value of the receiving coil. This is the parasitic resistance value of the receiving coil. The resistance value of the electrical load is used, and finally the equivalent capacitance value of the primary side adjustable capacitor array is adjusted according to the constraint relationship that the natural resonant angular frequency of the primary side resonant circuit is equal to the natural resonant angular frequency of the secondary side resonant circuit. The secondary-side adjustable capacitor array and the primary-side adjustable capacitor array are used to change the corresponding equivalent capacitance value according to the load change, so that the system maintains a parity-time symmetric state.

2. The WPT system with bilateral capacitor array according to claim 1, characterized in that: The high-frequency inverter circuit is a full-bridge inverter circuit composed of switching transistors Q1, Q2, Q3, and Q4.

3. The WPT system with bilateral capacitor array according to claim 2, characterized in that: The current detection circuit includes a current sensor and a zero-crossing comparator.

4. The WPT system with bilateral capacitor array according to any one of claims 1-3, characterized in that: Let the natural resonant angular frequency of the primary resonant circuit be... The natural resonant angular frequency of the secondary resonant circuit is The operating angular frequency of the output resonant current of the high-frequency inverter circuit is The system will follow The constraint relationship controls the operating state of the primary-side adjustable capacitor array, the secondary-side adjustable capacitor array, and the high-frequency inverter circuit, so that the system maintains a parity-time symmetric state.

5. The WPT system with bilateral capacitor array according to claim 1, characterized in that: Both the primary-side adjustable capacitor array and the secondary-side adjustable capacitor array are composed of multiple capacitor elements connected in parallel, and each capacitor element is connected to a circuit breaker.

6. An adaptive critical coupling coefficient adjustment method based on the bilateral capacitor array WPT system according to any one of claims 1-5, characterized in that, Includes the following steps: S1: The primary resonant current is acquired through the current detection circuit; S2: Determine the deviation of the current input impedance of the system from the input impedance under parity-time symmetry based on the current primary resonant current; S3: When the deviation value obtained in step S2 is greater than the preset threshold, the system critical coupling coefficient is changed by adjusting the equivalent capacitance values ​​of the primary adjustable capacitor array and the secondary adjustable capacitor array, so that the current system coupling coefficient is greater than or equal to the system critical coupling coefficient. S4: Adjust the operating angular frequency of the system according to the natural resonant angular frequencies of the primary and secondary resonant circuits after adjustment, so that the system can be restored to a parity-time symmetric state, and return to step S1 for repeated execution.

7. The adaptive critical coupling coefficient adjustment method for the bilateral capacitor array WPT system according to claim 6, characterized in that, The current input impedance of the system in step S2 according to Calculation, where This represents the fundamental component of the output voltage of the high-frequency inverter circuit. The current transmitting coil current; the input impedance in parity-time symmetrical state. according to Calculation, where This is the self-inductance value of the transmitting coil. This is the parasitic resistance value of the transmitting coil. The self-inductance value of the receiving coil. This is the parasitic resistance value of the receiving coil. The equivalent resistance of the electrical load, deviation value .

8. The adaptive critical coupling coefficient adjustment method for the bilateral capacitor array WPT system according to claim 6, characterized in that, In step S3, when the deviation value obtained in step S2 is greater than the preset threshold, the current coupling coefficient of the system is first measured by an LCR bridge and used as the critical coupling coefficient of the system. Then according to The constraint relationship is used to determine the equivalent capacitance value of the secondary adjustable capacitor array. ,in The self-inductance value of the receiving coil. This is the parasitic resistance value of the receiving coil. The resistance value of the electrical load is used, and finally the equivalent capacitance value of the primary-side adjustable capacitor array is adjusted according to the constraint relationship that the natural resonant angular frequency of the primary-side resonant circuit is equal to the natural resonant angular frequency of the secondary-side resonant circuit.

9. The adaptive critical coupling coefficient adjustment method for the WPT system with a two-sided capacitor array according to claim 8, characterized in that, according to Determine the system's operating angular frequency, where Let be the natural resonant angular frequency of the primary and secondary resonant circuits. The current coupling coefficient of the system. This indicates the quality factor of the secondary circuit.

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