Electric field resonance type wireless power transmission system based on switched capacitor dynamic compensation technology

Abstract

The application provides an electric field resonance type wireless power transmission system based on a switched capacitor dynamic compensation technology, which can maintain constant output power when the load changes and the coupling performance of a coupling mechanism changes. First, the equivalent circuit parameters of the coupling mechanism when the plate spacing changes and the plate offset changes are obtained through a finite element simulation software, then the adjustable external capacitor connected in parallel on both sides of the plate is adjusted to maintain the resonance of the internal self-capacitance of the coupling mechanism and the compensation inductance, and the adjustable compensation capacitor in the primary side and the secondary side compensation network is adjusted to maintain the constant output power when the mutual capacitance of the coupling mechanism changes, and finally the conduction angle of the adjustable capacitor is calculated. Compared with the prior art, the application does not need an additional power electronic converter and an adjustable inductor, has low cost and light weight, and can realize constant power output when the load changes, the plate spacing in the coupling mechanism changes and the plate offset changes.

Description

Technical Field

[0001] This invention relates to the field of wireless power transmission, and more specifically to a constant power control method for an electric field resonant wireless power transmission system based on switched capacitor dynamic compensation technology to resist offset. Background Technology

[0002] Wireless Power Transfer (WPT) technology is a wireless connection that transmits power through a high-frequency alternating electromagnetic field. It is currently widely used in smartphones, medical devices, electric vehicles, and industrial automation. Compared to wired charging, wireless charging offers advantages such as no plugging or unplugging, instant charging, and flexibility. In contrast to the four-coil magnetically coupled resonant wireless power transfer system, the four-coil compensated electric field resonant wireless power transfer technology boasts high power transmission and efficiency. However, when the plates within the coupling mechanism shift, the distance between the plates changes, or the load magnitude changes, it affects the system's constant output characteristics. Constant current charging followed by constant voltage charging is a common charging method for lithium-ion batteries. However, during constant current charging, the charging power varies significantly with charging time, leading to low utilization of power devices. Constant power charging, on the other hand, makes the charging current and charging voltage inversely proportional, providing a faster charging rate while also reducing heat sink size and mitigating battery aging issues.

[0003] Currently, when the coupling mechanism is offset, there are several ways to achieve constant power charging through the wireless power transmission system via electric field energy transfer: (1) DC-DC converter adjustment method: By controlling the duty cycle of the Boost converter and Buck converter, the input voltage is adjusted, the reactance of the active variable reactance rectifier is changed, the change of coupling capacitance is compensated, and constant power output is achieved. However, this method requires an additional DC-DC converter, which increases the number of circuit components and cost; (2) Resonant inductor adjustment method: By adjusting the adjustable inductor, the change of coupling capacitance is dynamically compensated, and the constant output of the system is maintained. Among them, there are three forms of adjustable inductors, including adjustable inductors composed of soft-switching transformers, adjustable inductors controlled by current, and adjustable inductors composed of phase-controlled inductors. However, the disadvantage of the first two types of adjustable inductors is that the constant inductor is not always the same. The value of the inductor must be the largest and a magnetic core is required, which increases the size, weight and cost of the system. The disadvantage of the third type of adjustable inductor is that it requires both a fixed inductor and a fixed capacitor, which increases the number of circuit components. (3) Capacitor matrix adjustment method: The value of the compensation capacitor is changed by switching the capacitor matrix. The problem with this method is that it requires multiple switching transistors. The compensation capacitor value obtained by the capacitor matrix is ​​discrete and cannot achieve stepless tuning. (4) Frequency adjustment method: The inverter frequency is adjusted to track the resonant frequency of constant voltage output and constant current output. The phase shift angle is controlled to adjust the gain, so that the output remains constant when the parameters of the electric field coupling mechanism change and the load is switched. However, it is only applicable to the transmitter tuning and the working frequency band is limited. It is not applicable when the dielectric characteristics in the electric field coupling mechanism change, the parameters of the compensation circuit components drift and the load changes significantly.

[0004] Therefore, designing a control method that can maintain constant output when the coupling performance of the coupling mechanism changes and the load changes is of great significance for achieving efficient energy transmission in electric field resonant wireless power transmission systems. Summary of the Invention

[0005] The purpose of this invention is to provide a control method for an electric field-coupled wireless power transfer system that maintains constant power output when the electrode plates of the coupling mechanism shift, the electrode plate distance changes, or the load changes. To achieve the above objective, the technical solution adopted by this invention is as follows:

[0006] The electric field resonant wireless power transfer system based on switched capacitor dynamic compensation technology includes a fully controlled H-bridge inverter, an M1-SS-M2 wireless power transfer stage, a diode bridge rectifier, and a load R. L The inverter operates in a complementary conduction mode, and the M1-SS-M2 wireless power transfer stage includes a primary-side adjustable compensation capacitor ΔC. f1 Primary-side loosely coupled transformer T1, primary-side adjustable external capacitor ΔC ex1 The coupling mechanism consists of four capacitor plates P1, P2, P3, and P4, with an adjustable external capacitor ΔC on the secondary side. ex2Secondary loosely coupled transformer T2, secondary adjustable compensation capacitor ΔC f2 ; among which, L f1 L1 is the self-inductance of the loosely coupled transformer in the primary-side compensation network, and L2 and L... f2 M1 represents the self-inductance of the loosely coupled transformer in the secondary compensation network, and M2 represents the mutual inductance of the loosely coupled transformers in the primary and secondary compensation networks, respectively. When the plates within the coupling mechanism shift, the distance between the plates changes, or the load changes, the constant output characteristics of the system will be affected. It is necessary to adjust the duty cycle of the switchable capacitor to dynamically adjust the capacitor value and achieve constant power output. The specific steps of the control method for the electric field resonant wireless power transfer system based on the switched capacitor dynamic compensation technology are as follows:

[0007] 1) Use finite element simulation software to simulate the self-capacitance C1, C2, and mutual capacitance C of the coupling mechanism when the plates shift and the distance between the plates changes. M The situation is changing;

[0008] 2) Calculate the primary-side adjustable external capacitor ΔC under different positions of the coupling mechanism and load variations, with the goal of constant system output power and zero phase angle of inverter output voltage and current. ex1 Secondary adjustable external capacitor ΔC ex2 Primary-side adjustable compensation capacitor ΔC f1 and the secondary adjustable compensation capacitor ΔC f2 ;

[0009] 3) Based on the working principle of soft-switching controllable capacitors, ΔC ex1 ΔC ex2 ΔC f1 and ΔC f2 This is converted into the conduction angle of a soft-switching controllable capacitor, ensuring a constant output power.

[0010] In step 1), the parametric scanning function of the finite element simulation software is used to simulate the offset of the coupling mechanism plates and the change in distance between the plates, obtaining the distance between any two plates P. i and P j The coupling capacitance C between them ij (i = 1, 2, 3, 4, i ≠ j), based on the two-port network characteristics of the coupling mechanism, the self-capacitance C1, C2 and mutual capacitance C in its equivalent excitation current source model are... M for

[0011]

[0012] In step 2), the electric field resonance constant power output control based on switched capacitor dynamic compensation technology is achieved by calculating the adjustable external capacitor ΔC. ex1 ΔC ex2 and adjustable compensation capacitor ΔCf1 ΔC f2 Achieve constant power output when the coupling mechanism changes.

[0013] An adjustable capacitor ΔC is connected in parallel across the two ends of the coupling mechanism. ex1 and ΔC ex2 At that time, the self-capacitance C in the equivalent excitation voltage source model v1 C v2 and mutual capacitance C vm for

[0014]

[0015] The resonance condition of the proposed system is

[0016]

[0017] Where ω is the system's resonant angular frequency.

[0018] Based on the equivalent model of the electric field resonant wireless power transfer system using switched capacitor dynamic compensation technology, Kirchhoff's voltage law can be applied.

[0019]

[0020] Among them, I f1 I1, I2, I f2 V represents the current flowing through the four loops. AB ΔC represents the effective value of the fundamental wave of the inverter's output square wave voltage. f1 With ΔC f2 C f1 With C f2 The adjustment amount, r f1 r1, r2 and r f2 These are the internal resistances of the four circuits, R. e This is the equivalent load resistance at the input of the diode rectifier bridge.

[0021] The system's output power P out and input impedance Z in for

[0022]

[0023] To meet the system's requirement of constant output power P d To achieve zero phase angle at inverter output, the following conditions must be met.

[0024]

[0025] Combining equations (2) to (6), and neglecting the internal resistance of each circuit to simplify the calculation, we can obtain:

[0026]

[0027] In the formula, ΔC ex1 and ΔC ex2 With output power P d Irrelevant, ΔC f1 With ΔC f2 With output power P d Therefore, ΔC can be adjusted first. ex1 and ΔC ex2 Let the system resonate, then adjust ΔC. f1 With ΔC f2 The fact that the system output power remains constant demonstrates that the proposed electric field resonant wireless power transfer system based on switched capacitor dynamic compensation technology can maintain constant power output when the plates in the coupling mechanism shift, the distance between the plates changes, and the load changes.

[0028] The soft-switching controllable capacitor in step 3) is a PWM-modulated switching capacitor, consisting of two anti-parallel series-connected metal-oxide-semiconductor field-effect transistors (MOSFETs) S1 and S2 and a capacitor C. c Connected in parallel, and then with capacitor C d Composed of series connections, the MOSFET conduction angle β is controlled by detecting the current flowing through the compensation capacitor branch. x (x=ΔC ex1 ,ΔC ex2 ,ΔC f1 ,ΔC f2 Change capacitor C c The time of introduction and bypassing is used to realize the equivalent capacitance Δy (y = C). ex1 C ex2 C f1 C f2 The relationship between the conduction angle and the equivalent capacitance Δy of the soft-switching controllable capacitor is as follows:

[0029]

[0030] The ΔC calculated in step 2) ex1 ΔC ex2 ΔC f1 ΔC f2 The value of β is obtained by using the bisection method according to equation (8). ΔCex1 β ΔCex2 β ΔCf1 β ΔCf2 This ensures that the system output power remains constant.

[0031] Compared with the prior art, the significant advantages of this invention are: it does not require an additional power electronic converter and adjustable inductor, is low in cost and light in weight, and can achieve stepless tuning and constant power output when the electrode plates in the coupling mechanism are offset, the electrode plate distance changes and the load changes.

[0032] The following will provide a detailed description with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] Figure 1 This is an electric field-coupled resonant wireless power transfer system based on a four-coil structure compensated by a soft-switching controllable capacitor;

[0034] Figure 2 It is a coupling mechanism;

[0035] Figure 3 An equivalent model of an electric field-coupled resonant wireless power transfer system based on a four-coil structure with soft-switching controllable capacitors for compensation.

[0036] Figure 4 It is a soft-switching controllable capacitor structure;

[0037] Figure 5 The output power waveform is shown when the load changes from 100Ω to 50Ω and then to 25Ω.

[0038] Figure 6 The system output power waveform is shown when the vertical distance between the plates of the coupling mechanism changes from 9cm to 11cm and then to 13cm.

[0039] Figure 7 The output power waveform of the system when the electrode plate on the same side is offset from 0cm to 15cm and then to 30cm is given.

[0040] Specific implementation mode

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0042] like Figure 1 As shown, the electric field resonant wireless power transfer system based on switched capacitor dynamic compensation technology includes a fully controlled H-bridge inverter, an M1-SS-M2 wireless power transfer stage, a diode bridge rectifier, and a load R. L The inverter operates in a complementary conduction mode, and the M1-SS-M2 wireless power transfer stage includes a primary-side adjustable compensation capacitor ΔC. f1 Primary-side loosely coupled transformer T1, primary-side adjustable external capacitor ΔC ex1 The coupling mechanism consisting of four capacitor plates P1, P2, P3, and P4, as follows: Figure 2 As shown, the adjustable external capacitor ΔC on the secondary side ex2Secondary loosely coupled transformer T2, secondary adjustable compensation capacitor ΔC f2 ; among which, L f1 L1 is the self-inductance of the loosely coupled transformer in the primary-side compensation network, and L2 and L... f2 M1 represents the self-inductance of the loosely coupled transformer in the secondary compensation network, and M2 represents the mutual inductance of the loosely coupled transformers in the primary and secondary compensation networks, respectively. When the plates within the coupling mechanism shift, the distance between the plates changes, or the load changes, the constant output characteristics of the system will be affected. It is necessary to adjust the duty cycle of the switchable capacitor to dynamically adjust the capacitor value and achieve constant power output. The specific steps of the control method for the electric field resonant wireless power transfer system based on the switched capacitor dynamic compensation technology are as follows:

[0043] 1) Use finite element simulation software to simulate the self-capacitance C1, C2, and mutual capacitance C of the coupling mechanism when the plates shift and the distance between the plates changes. M The situation is changing;

[0044] 2) Calculate the primary-side adjustable external capacitor ΔC under different positions of the coupling mechanism and load variations, with the goal of constant system output power and zero phase angle of inverter output voltage and current. ex1 Secondary adjustable external capacitor ΔC ex2 Primary-side adjustable compensation capacitor ΔC f1 and the secondary adjustable compensation capacitor ΔC f2 ;

[0045] 3) Based on the working principle of soft-switching controllable capacitors, ΔC ex1 ΔC ex2 ΔC f1 and ΔC f2 This is converted into the conduction angle of a soft-switching controllable capacitor, ensuring a constant output power.

[0046] In step 1), the parametric scanning function of the finite element simulation software is used to simulate the offset of the coupling mechanism plates and the change in distance between the plates, obtaining the distance between any two plates P. i and P j The coupling capacitance C between them ij (i = 1, 2, 3, 4, i ≠ j), based on the two-port network characteristics of the coupling mechanism, the self-capacitance C1, C2 and mutual capacitance C in its equivalent excitation current source model are... M for

[0047]

[0048] In step 2), the electric field resonance constant power output control based on switched capacitor dynamic compensation technology is achieved by calculating the adjustable external capacitor ΔC. ex1 ΔC ex2 and adjustable compensation capacitor ΔCf1 ΔC f2 The value achieves constant power output when the coupling mechanism changes.

[0049] An adjustable capacitor ΔC is connected in parallel across the two ends of the coupling mechanism. ex1 and ΔC ex2 At that time, the self-capacitance C in the equivalent excitation voltage source model v1 C v2 and mutual capacitance C vm for

[0050]

[0051] The resonance condition of the proposed system is

[0052]

[0053] Where ω is the system's resonant angular frequency.

[0054] The equivalent model of the electric field resonant wireless power transfer system based on switched capacitor dynamic compensation technology is as follows: Figure 3 As shown, from Kirchhoff's voltage law, we can obtain...

[0055]

[0056] Among them, I f1 I1, I2, I f2 V represents the current flowing through the four loops. AB ΔC represents the effective value of the fundamental wave of the inverter's output square wave voltage. f1 With ΔC f2 C f1 With C f2 The adjustment amount, r f1 r1, r2 and r f2 These are the internal resistances of the four circuits, R. e This is the equivalent load resistance at the input of the diode rectifier bridge.

[0057] The system's output power P out and input impedance Z in for

[0058]

[0059] To meet the system's requirement of constant output power P d To achieve zero phase angle at inverter output, the following conditions must be met.

[0060]

[0061] Combining equations (2) to (6), and neglecting the internal resistance of each circuit to simplify the calculation, we can obtain:

[0062]

[0063] In the formula, ΔC ex1 and ΔC ex2 With output power P d Irrelevant, ΔC f1 With ΔC f2 With output power P d Therefore, ΔC can be adjusted first. ex1 and ΔC ex2 Let the system resonate, then adjust ΔC. f1 With ΔC f2 The fact that the system output power remains constant demonstrates that the proposed electric field resonant wireless power transfer system based on switched capacitor dynamic compensation technology can maintain constant power output when the plates in the coupling mechanism shift, the distance between the plates changes, and the load changes.

[0064] The soft-switching controllable capacitor in step 3) is a PWM-modulated switching capacitor, such as... Figure 4 As shown, it consists of two metal-oxide-semiconductor field-effect transistors (MOSFETs) connected in reverse series and a capacitor C. c Connected in parallel, and then with capacitor C d Composed of series connections, the MOSFET conduction angle β is controlled by detecting the current flowing through the compensation capacitor branch. x (x=ΔC ex1 ,ΔC ex2 ,ΔC f1 ,ΔC f2 Change capacitor C c The time of introduction and bypassing is used to realize the equivalent capacitance Δy (y = C). ex1 C ex2 C f1 C f2 The relationship between the conduction angle and the equivalent capacitance Δy of the soft-switching controllable capacitor is as follows:

[0065]

[0066] The ΔC calculated in step 2) ex1 ΔC ex2 ΔC f1 ΔC f2 The value of β is obtained by using the bisection method according to equation (8). ΔCex1 β ΔCex2 β ΔCf1 β ΔCf2 This ensures that the system output power remains constant.

[0067] Compared with the prior art, the significant advantages of this invention are: it does not require an additional power electronic converter or adjustable inductor, is low in cost and light in weight, and can achieve stepless tuning and constant power output when the electrode plates in the coupling mechanism are offset, the electrode plate distance changes and the load changes.

[0068] Example: Simulation Result Analysis

[0069] Build a coupled mechanism model in the finite element simulation software COMSOL, such as Figure 2 As shown, from top to bottom on the left are P1 and P2, and from top to bottom on the right are P3 and P4. Each electrode plate is 60cm long, 60cm wide, and 1cm thick. The distance between electrodes on the same side is 5cm, and the vertical distance between electrodes is 9cm. Using the parametric scanning function in the finite element simulation software, the mutual capacitance C of the coupling mechanism is obtained when the vertical distance between the electrodes is 9cm, 11cm, and 13cm respectively. M The mutual capacitances C1 and C2 are 21.247 pF, 17.586 pF, and 14.985 pF, respectively; the self-capacitances C1 and C2 are 34.125 pF, 30.913 pF, and 28.631 pF, respectively; and the self-capacitances C2 and C3 are 33.579 pF, 30.067 pF, and 27.399 pF, respectively. When the two plates P3 and P4 on the same side are simultaneously offset by 0 cm, 15 cm, and 30 cm, the mutual capacitances C of the coupling mechanism are obtained. M The capacitances are 21.247pF, 16.845pF, and 10.608pF respectively, the self-capacitance C1 is 34.125pF, 32.538pF, and 29.386pF respectively, and the self-capacitance C2 is 33.579pF, 32.067pF, and 28.937pF respectively.

[0070] by Figure 1 Taking the electric field-coupled resonant wireless power transfer system based on a four-coil structure with soft-switching controllable capacitors as an example, a model is built using circuit simulation software. The DC voltage V on the input side of the inverter circuit is shown. dc The voltage is 100V, the system resonant angular frequency ω is 200kHz, and the self-inductance L of the loosely coupled transformer T1 in the primary compensation network is... f1 L1 and L2 have inductances of 8mH and 17mH respectively, mutual inductance M1 is 0.7mH, and the self-inductance L of the loosely coupled secondary transformer T2 is... f2 L2 has a current of 8mH and L2 has a current of 17mH, mutual inductance M2 is 0.7mH, and filter capacitor C is... f The value is 1μF; when the system's rated output power is 100W, the load R L The impedance is 100Ω, so no adjustable compensation capacitor is needed. The primary-side compensation capacitor C... f1 The secondary-side compensation capacitor C is 79.157pF. f2The capacitance is 79.157pF, and the primary-side adjustable external capacitor ΔC is... ex1 The capacitance is 12.755pF, and the adjustable external capacitor ΔC on the secondary side is also 12.755pF. ex2 It is 13.301pF.

[0071] When the load changes, the distance between the plates within the coupling mechanism changes, or the plates P3 and P4 on the same side of the coupling mechanism shift simultaneously, an adjustable capacitor needs to be connected. The primary-side adjustable compensation capacitor ΔC... f1 and the secondary adjustable compensation capacitor ΔC f2 C c 8.873nF, C d The primary-side adjustable external capacitor ΔC is 23.415nF. ex1 and the adjustable external capacitor ΔC on the secondary side ex2 C c It is 7.941 pF, C d It is 15.441 pF, while ΔC f1 ΔC f2 ΔC ex1 ΔC ex2 MOSFET conduction angle β ΔCf1 β ΔCf2 β ΔCex1 β ΔCex2 It is determined by the operating conditions.

[0072] First, the constant output power characteristics of the electric field resonant wireless power transfer system based on switched capacitor dynamic compensation technology were verified under load changes: when the coupling mechanism does not shift, only the load R... L When changed, it will not affect the resonance condition within the system; therefore, the adjustable capacitor ΔC connected in parallel across the plates... ex1 ΔC ex2 The value remains unchanged; when the load is switched to 50Ω, ΔC is obtained from equation (7). f1 The value is 10.12 nF, and ΔC is... f2 The MOSFET conduction angle β is 20.241 nF, obtained from equation (8). ΔCf1 1.9887, β ΔCf2 It is 2.6125; when the load R L When switching to 25Ω, ΔC is obtained from equation (7). f1 The value is 5.7829 nF, and ΔC f2 The MOSFET conduction angle β is 23.132nF, obtained from equation (8). ΔCf1 1.4481, β ΔCf2 The output power of the system using dynamic compensation technology based on switched capacitors when the load changes is 2.919; Figure 5As shown in the figure, the output power is within 0-0.02s when the load is 100Ω, the output power is within 0.02-0.04s when the load is 50Ω, and the output power is within 0.04-0.06s when the load is 25Ω. It can be seen that the system basically achieves a constant power output of 100W when the load changes.

[0073] Next, we verify the constant output power characteristics of the electric field resonant wireless power transmission system based on switched capacitor dynamic compensation technology when the distance between the plates inside the coupling mechanism changes: When the distance between the plates inside the coupling mechanism changes, the resonance condition in the system will change. When the vertical distance between the plates is 11cm, the adjustable external capacitor ΔC of the primary side is obtained from equation (7). ex1 The capacitance is 13.328pF, and the adjustable external capacitor ΔC on the secondary side is also 13.328pF. ex2 The primary-side adjustable compensation capacitor ΔC is 14.174pF. f1 The secondary-side adjustable compensation capacitor ΔC is 19.193nF. f2 The MOSFET conduction angle β is 19.193nF, obtained from equation (8). ΔCex1 β ΔCex22 β ΔCf1 β ΔCf2 The values ​​are 2.551, 2.6574, 2.5464, and 2.5464 respectively; when the vertical distance between the plates is 13cm, ΔC is obtained from equation (7). ex1 It is 13.899pF, ΔC ex2 The value is 15.131 pF, and ΔC f1 The value is 12.613 nF, and ΔC is... f2 The MOSFET conduction angle β is 12.613nF, obtained from equation (8). ΔCex1 β ΔCex22 β ΔCf1 β ΔCf2 The corresponding values ​​are 2.6199, 2.8482, 2.1671, and 2.1671, respectively. The system output power using dynamic compensation technology based on switched capacitors when the vertical distance between the plates changes is as follows: Figure 6 As shown in the figure, the output power is 9cm when the vertical distance is between 0 and 0.01s, 11cm when the vertical distance is between 0.01 and 0.02s, and 13cm when the vertical distance is between 0.02 and 0.03s. It can be seen that the output power is about 100W when the vertical distance changes, thus achieving constant power output.

[0074] Finally, it was verified that the distance between the plates in the coupling mechanism did not change, but when the plates P3 and P4 on the same side of the coupling mechanism shifted simultaneously, the constant output power characteristics of the electric field resonant wireless power transmission system based on the switching capacitor dynamic compensation technology were obtained: When the plates P3 and P4 on the same side of the coupling mechanism shifted simultaneously by 15cm, the primary adjustable external capacitor ΔC was obtained from equation (7). ex1 The capacitance is 11.2pF, and the adjustable external capacitor ΔC on the secondary side is also 11.2pF. ex2 The primary-side adjustable compensation capacitor ΔC is 11.671pF. f1 The secondary-side adjustable compensation capacitor ΔC is 16.739nF. f2 The MOSFET conduction angle β is 16.739 nF, obtained from equation (8). ΔCex1 β ΔCex22 β ΔCf1 β ΔCf2 The values ​​are 2.3361, 2.3813, 2.4067, and 2.4067 respectively. When the same-side plates P3 and P4 are simultaneously offset by 30cm, ΔC is obtained from equation (7). ex1 It is 10.673pF, ΔC ex2 The value is 11.122 pF, and ΔC is... f1 The value is 7.2318 nF, and ΔC is... f2 The MOSFET conduction angle β is 7.2318nF, obtained from equation (8). ΔCex1 β ΔCex22 β ΔCf1 β ΔCf2 The corresponding values ​​are 2.2857, 2.3286, 1.6908, and 1.6908, respectively. The system output power using dynamic compensation technology based on switched capacitors when the same-side plates P3 and P4 within the coupling mechanism simultaneously shift is as follows: Figure 7 As shown in the figure, the output power is within 0-0.01s when the plate is offset by 0cm, the output power is within 0.01-0.02s when plates P3 and P4 are offset by 15cm simultaneously, and the output power is within 0.02-0.03s when plates P3 and P4 are offset by 30cm simultaneously. It can be seen that the output power of the system is about 100W when the plates P3 and P4 on the same side are offset by different distances, thus achieving constant power output.

[0075] The above simulations demonstrate that the electric field resonant wireless power transmission system based on switched capacitor dynamic compensation technology proposed in this invention patent can achieve constant power output under load changes, as well as changes in the vertical distance between the plates in the coupling mechanism and the offset of the plates on the same side.

[0076] As can be seen from the above embodiments, the method proposed in this invention can effectively achieve constant output power of the electric field resonant wireless power transmission system when the load and coupling mechanism change.

[0077] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. An electric field resonant wireless power transfer system based on switched capacitor dynamic compensation technology, comprising a fully controlled H-bridge inverter, an M1-SS-M2 wireless power transfer stage, a diode bridge rectifier, and a load. R L The inverter operates in a complementary conduction mode, and the M1-SS-M2 wireless power transfer stage includes a primary-side adjustable compensation capacitor Δ. C f1 Primary-side compensation capacitor C f1 Primary-side loosely coupled transformer T1, primary-side adjustable external capacitor Δ C ex1 The coupling mechanism consists of four capacitor plates P1, P2, P3, and P4, with an adjustable external capacitor Δ on the secondary side. C ex2 Secondary loosely coupled transformer T2, secondary adjustable compensation capacitor Δ C f2 Secondary side compensation capacitor C f2 ; in, L f1 The primary-side self-inductance of the primary-side loosely coupled transformer T1, L 1 represents the secondary self-inductance of the primary-side loosely coupled transformer T1. L 2 represents the primary-side self-inductance of the loosely coupled secondary transformer T2. L f2 For the secondary side self-inductance of the loosely coupled transformer T2, M 1 represents the mutual inductance of the primary-side loosely coupled transformer T1. M 2 represents the mutual inductance of the secondary loosely coupled transformer T2; the primary adjustable compensation capacitor Δ C f1 Primary-side compensation capacitor C f1 The primary winding of the loosely coupled transformer T1 is connected in series with the primary winding and then connected between the two output terminals of the fully controlled H-bridge inverter. One end of the secondary winding of the loosely coupled transformer T1 is connected to the primary adjustable external capacitor Δ. C ex1 The other end of the secondary winding of the primary-side loosely coupled transformer T1 is connected to the common terminal of the first plate P1, and the other end of the primary-side adjustable external capacitor Δ C ex1 The primary-side self-inductance of the primary-side loosely coupled transformer T1 is connected to the common terminal of the second plate P2. L f1 Secondary self-perception L 1. Compensate the primary side capacitors respectively C f1 Primary-side adjustable external capacitor Δ C ex1 The primary side self-capacitance of the coupling mechanism consisting of four capacitor plates P1, P2, P3, and P4; one end of the primary winding of the loosely coupled secondary transformer T2 and the adjustable external capacitor Δ on the secondary side. C ex2 The common terminal of the third plate P3 is connected to the other end of the primary winding of the loosely coupled secondary transformer T2, and the other end of the primary winding is connected to the adjustable external capacitor Δ. C ex2 The common terminal of the fourth plate P4 is connected to the secondary winding of the loosely coupled transformer T2 on the secondary side and the secondary compensation capacitor. C f2 Secondary adjustable compensation capacitor Δ C f2 Connected in series between the two input terminals of the diode bridge rectifier, the filter capacitor... C f and load R L After being connected in parallel between the two output terminals of the diode bridge rectifier, the primary-side self-inductance of the secondary loosely coupled transformer T2 is... L 2. Secondary side self-induction L f2 Each compensates for the adjustable external capacitor Δ on the secondary side. C ex2 The secondary self-capacitance and secondary compensation capacitor of the coupling mechanism consisting of four capacitor plates P1, P2, P3, and P4 C f2 When the plates in the coupling mechanism shift, the distance between the plates changes, or the load changes, the constant output characteristics of the system will be affected. It is necessary to adjust the duty cycle of the switchable capacitor to dynamically adjust the capacitor value and achieve constant power output. The specific steps of the control method for the electric field resonant wireless power transfer system based on switched capacitor dynamic compensation technology are as follows: 1) Simulate the self-capacitance of the coupling mechanism when the plates shift and the distance between the plates changes using finite element simulation software. C 1. C 2 and mutual capacitance C M The situation is changing; 2) Calculate the primary-side adjustable external capacitor Δ under different positions of the coupling mechanism and load variations, with the goal of constant system output power and zero phase angle of inverter output voltage and current. C ex1 Secondary adjustable external capacitor Δ C ex2 Primary-side adjustable compensation capacitor Δ C f1 and the secondary adjustable compensation capacitor Δ C f2 ; 3) Based on the working principle of soft-switching controllable capacitors, Δ C ex1 Δ C ex2 Δ C f1 and Δ C f2 This is converted into the conduction angle of a soft-switching controllable capacitor, ensuring a constant output power.

2. The electric field resonant wireless power transfer system based on switched capacitor dynamic compensation technology according to claim 1, characterized in that: In step 1), the parametric scanning function of the finite element simulation software is used to simulate the offset of the coupling mechanism plates and the change in distance between the plates, obtaining the distance between any two plates P. i and P j Coupling capacitance between C ij ( i =1, 2,3, 4, i ≠ j Based on the two-port network characteristics of the coupling mechanism, the self-capacitance in its equivalent excitation current source model... C 1. C 2 and mutual capacitance C M for (1) In step 2), the electric field resonance constant power output control based on switched capacitor dynamic compensation technology is achieved by calculating the adjustable external capacitor Δ. C ex1 Δ C ex2 and adjustable compensation capacitor Δ C f1 Δ C f2 The value achieves constant power output when the coupling mechanism changes; An adjustable capacitor Δ is connected in parallel across both ends of the coupling mechanism. C ex1 and Δ C ex2 At that time, the self-capacitance in the equivalent excitation voltage source model C v1 , C v2 and mutual capacitance C vm for (2) The resonance condition of the proposed system is (3) in, ω This is the system's resonant angular frequency; Based on the equivalent model of the electric field resonant wireless power transfer system using switched capacitor dynamic compensation technology, Kirchhoff's voltage law can be applied. (4) in, I f1 , I 1. I 2. I f2 These represent the currents flowing through the four loops, V AB ∆ is the effective value of the fundamental wave of the inverter output square wave voltage. C f1 With ∆ C f2 They are respectively C f1 and C f2 The adjustment amount, r f1 , r 1. r 2 and r f2 These are the internal resistances of the four circuits, R e This is the equivalent load resistance at the input of the diode rectifier bridge; System output power P out and input impedance Z in for (5) To meet the system's requirement of constant output power P d To achieve zero phase angle at inverter output, the following conditions must be met. (6) Combining equations (2) to (6), and ignoring the internal resistance of each circuit to simplify the calculation, we can obtain: (7) In the formula, V ab This represents the effective value of the fundamental wave of the inverter's output square wave voltage. R eq Δ is the equivalent load resistance at the input of the diode rectifier bridge. C ex1 and Δ C ex2 With output power P d Irrelevant, ∆ C f1 With ∆ C f2 With output power P d Therefore, Δ can be adjusted first. C ex1 and Δ C ex2 Let the system resonate, then adjust ∆ C f1 With ∆ C f2 The fact that the system output power is kept constant demonstrates that the proposed electric field resonant wireless power transfer system based on switched capacitor dynamic compensation technology can maintain constant power output when the plates in the coupling mechanism are offset, the distance between the plates changes, and the load changes. The soft-switching controllable capacitor in step 3) is a PWM-modulated switched capacitor, consisting of two anti-parallel series metal-oxide-semiconductor field-effect transistors (MOSFETs) and a capacitor. C c Connected in parallel, and then with a capacitor. C d Composed of series connections, the MOSFET conduction angle is controlled by detecting the current flowing through the compensation capacitor branch. β x ( x =Δ C ex1 ,Δ C ex2 , ∆ C f1 , ∆ C f2 Change the capacitance C c The time of introduction and bypassing is used to realize the equivalent capacitance ∆ y ( y = C ex1 , C ex2 , C f1 , C f2 The change in the conduction angle and the equivalent capacitance ∆ of the soft-switching controllable capacitor. y The relationship is (8) The Δ calculated in step 2) C ex1 Δ C ex2 ∆ C f1 ∆ C f2 The value of , and according to equation (8), the corresponding MOSFET conduction angle can be obtained using the bisection method. β ΔCex1 , β ΔCex2 , β ∆Cf1 , β ∆Cf2 This ensures that the system output power remains constant.

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