Adaptive resonance WPT system based on energy negative feedback

Abstract

The invention discloses an adaptive resonance WPT system based on negative energy feedback, comprising a resonance network and a reactive power pickup circuit; wherein the resonance network comprises a transmission network and a receiving network; the reactive power pickup circuit is connected in series between an excitation voltage source of the transmission network and a transmitting end resonance capacitor; the reactive power pickup circuit comprises a rectifier capacitor, a third MOSFET tube and a second MOSFET tube, the third MOSFET tube and a fourth MOSFET tube are connected in series and then connected in parallel with the rectifier capacitor; one end of the transmitting end resonance capacitor is connected between the third MOSFET tube and the fourth MOSFET tube; one end of the excitation power supply is connected between the rectifier capacitor and the fourth MOSFET tube; reactive power negative feedback is realized by conducting and adjusting the phase of the third MOSFET tube and the fourth MOSFET tube, thereby realizing adaptive resonance of the WPT system.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transmission, and in particular to an adaptive resonance WPT system based on negative energy feedback. Background Art

[0002] Stable energy supply is a key link to ensure the normal deployment of such equipment. The process of charging and replacing batteries by salvaging is complicated and labor-intensive, and the interface of underwater contact power supply is prone to wear and has a short lifespan. In comparison, wireless power transmission technology (WPT) can achieve non-contact energy supply through high-frequency electromagnetic fields, and has great advantages in sealing and convenience. However, due to the instability of the underwater environment, there is high-frequency random interference in the relative position of the coupling mechanism, and the self-inductance between the coupling coils will also change accordingly. The introduced impedance mismatch problem can easily induce system detuning, and the power transmission capacity is difficult to guarantee. In severe cases, it may even cause non-monotonic changes in the power curve, resulting in failure of the control link.

[0003] To solve the above problems, many impedance control technology routes have been proposed. The principle of cascaded DC-DC converter is the simplest and most versatile, but this type of technology has a low power density and can only perform pure resistive control, which makes it difficult to deal with the detuning problem caused by reactance changes. The non-monotonic relationship between duty cycle and output power caused by parasitic parameters also places high demands on parameter accuracy. Active rectification technology replaces diodes with active switching devices such as MOSFET, so that a single circuit has both rectification and impedance regulation capabilities, and has higher power density. However, since this type of topology is mostly at the end of the system and will introduce a zero-power mode that does not supply energy to the load, the reactance control effect is relatively limited and will weaken the power transmission capability to a certain extent.

[0004] The essence of system detuning is that impedance changes cause an offset between the natural frequency and the operating frequency of the WPT system. Therefore, phase tracking through frequency adjustment is an efficient impedance control solution. Different solutions in the prior art only sample the current at the time when the switch is turned off and update the frequency by judging whether it is near 0, omitting the phase calculation link of voltage and current, but it is necessary to ensure that the system works in a loosely coupled area. Another proposed frequency control scheme that can achieve excellent performance in the over-coupling area, but also pointed out its poor performance in the under-coupling area. There is also a related prior art that provides a frequency control method analyzed from a fractional order perspective, which can achieve decoupling between the control strategy and the coupling strength, but due to the complexity of the control algorithm, a large voltage ripple will appear in the dynamic response process, and zero-phase frequency tracking is performed by real-time detection of the amplitude and phase of the input voltage and current, and a frequency locker is designed to ensure that the system automatically tracks the high-frequency resonance point when the frequency is split, which increases the achievable range of frequency tracking, but the detection circuit contains many power amplifiers and switching devices, which has an adverse effect on power density and cost.

[0005] By reconstructing the resonant network and changing the value of the resonant inductor or capacitor, the natural frequency of the system can be corrected to the operating frequency and detuning correction can be achieved. Among them, constructing a capacitor-inductor matrix and using switching devices to control the number of components involved in the resonance process is the most direct control method, but this solution can only achieve discrete control and the system volume is too large. A bidirectional switch is connected in parallel at both ends of a larger resonant capacitor, and the working time of the resonant capacitor in a single working cycle is changed by controlling the conduction time of the switch tube, so as to achieve the purpose of adjusting the equivalent capacitance value, and the number of components is reduced. However, the switching device will directly bear the resonant voltage, and the stress level is relatively high.

[0006] In summary, the auxiliary circuits of existing detuning correction technologies are large in size, have complex algorithms, and have high requirements for parameter accuracy, which are not sufficient to meet the assembly requirements and response rate requirements of marine equipment. Summary of the invention

[0007] In order to solve the problems existing in the above-mentioned prior art, the present invention provides an adaptive resonant WPT system based on energy negative feedback, which introduces reactive power by constructing a detuned state in the resonant network. The reactive power in turn corrects the energy negative feedback logic of the detuned state to ensure that the system spontaneously maintains a resonant state. Its auxiliary circuit is small in size, does not require additional algorithm control, and has high accuracy.

[0008] In order to achieve the above technical objectives, the present invention provides the following technical solutions: an adaptive resonance WPT system based on energy negative feedback, comprising:

[0009] Resonant network and reactive power pickup circuit; wherein the resonant network includes a transmitting network and a receiving network; the transmitting network is sequentially connected in series with an excitation power supply, a transmitting end resonant capacitor, a transmitting coil and a transmitting end resistor;

[0010] The reactive power pickup circuit is connected in series between the excitation voltage source and the transmitting end resonant capacitor;

[0011] The reactive power pickup circuit includes a rectifier capacitor, a third MOSFET tube and a second MOSFET tube, and the third MOSFET tube and the fourth MOSFET tube are connected in series and then connected in parallel with the rectifier capacitor;

[0012] One end of the transmitting end resonant capacitor is connected between the third MOSFET tube and the fourth MOSFET tube;

[0013] One end of the excitation power supply is connected between the rectifier capacitor and the fourth MOSFET tube;

[0014] By adjusting the conduction and phase of the third MOSFET tube and the fourth MOSFET tube, reactive power negative feedback is achieved, thereby realizing adaptive resonance of the WPT system.

[0015] Optionally, when the reactive current changes from negative to positive, the third MOSFET is turned on and the fourth MOSFET is turned off; when the reactive current changes from positive to negative, the third MOSFET is turned off and the fourth MOSFET is turned on;

[0016] When the total reactance is inductive, the phase of the third MOSFET tube and the fourth MOSFET tube lags by 90°, and when the total reactance is inductive, the phase of the third MOSFET tube and the fourth MOSFET tube leads by 90°;

[0017] The reactive current is the reactive current of the input resonant current in the resonant network, and the total reactance is the total reactance of the equivalent resistance of the resonant capacitor, the transmitting coil, and the mutual inductance between the transmitting network and the receiving network in the resonant network.

[0018] Optionally, the excitation power supply includes a first MOSFET tube, a second MOSFET tube and a voltage source, the first MOSFET tube and the second MOSFET tube are connected in series with the voltage source, the first MOSFET tube and the second MOSFET tube serve as the positive pole of the excitation power supply, and the second MOSFET tube and the voltage source serve as the negative pole of the excitation power supply; the positive pole of the excitation power supply is connected to one end of the transmitting coil; the negative pole of the excitation power supply is connected between the rectifier capacitor and the fourth MOSFET tube.

[0019] Optionally, the receiving network includes a receiving coil, a receiving end resistor, a receiving end resonant capacitor, a rectifier circuit, and an actual load, wherein the receiving coil, the receiving end resistor, and the receiving end resonant capacitor are connected in series in sequence, a rectifier circuit is connected in series between the receiving coil and the receiving end resonant capacitor, and the rectifier circuit is connected in parallel with the actual load.

[0020] Optionally, the rectifier circuit adopts a full-bridge rectifier circuit.

[0021] Optionally, the convergence of the adaptive resonant WPT system is judged through modal analysis and mathematical models.

[0022] Optionally, the rectifying capacitor is positively correlated with the time taken for the adaptive resonance to reach stability.

[0023] Optionally, the magnitude of the resonant current of the adaptive resonance of the WPT system is a ratio of the excitation source to the sum of the equivalent resistance and the transmitting end resistance.

[0024] The present invention has the following technical effects:

[0025] The present invention proposes a detuning correction scheme based on negative energy feedback. The scheme extracts and stores the energy contained in the reactive current in the detuned state through an energy pickup circuit composed of two active switching devices and a storage capacitor. Subsequently, by adjusting the phase of the switching device in the energy pickup circuit and selecting the appropriate time to inject the picked-up reactive energy for a second time, this part of the energy can be converted into active power, thereby achieving detuning correction without changing the system frequency and the parameters of the resonant components. Compared with existing research, this method only requires two switching devices and a storage capacitor to maintain the resonant state when the system's own impedance fluctuates over a large range. More importantly, since the negative energy feedback characteristic used in the present invention is a spontaneous phenomenon of the resonant system, it does not require additional detection and control algorithms, and its dynamic characteristics and versatility in detuning correction are extremely advantageous. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0027] Figure 1 A schematic diagram of a general WPT network structure provided by an embodiment of the present invention;

[0028] Figure 2 A schematic diagram of a detuning correction idea based on reactive power secondary shaping provided in an embodiment of the present invention;

[0029] Figure 3 A WPT system with energy negative feedback function provided by an embodiment of the present invention;

[0030] Figure 4 A logic block diagram of realizing detuning correction through negative energy feedback provided in an embodiment of the present invention;

[0031] Figure 5 The modal diagrams of the initial active and reactive currents provided in the embodiments of the present invention, wherein (a) is a structural diagram of mode 1, (b) is a structural diagram of mode 2, (c) is a structural diagram of mode 3, and (d) is a structural diagram of mode 4;

[0032] Figure 6 A schematic diagram of the key parameter convergence process provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Wireless power transmission technology can provide a stable energy supply for the normalized deployment of unmanned intelligent devices. However, the uncertainty of the working environment, especially the impact of ocean currents, wind and waves on impedance in marine application scenarios, will cause the system to be detuned, and the introduced reactive power will greatly reduce the power transmission capacity of the system, and even cause the power curve to become non-monotonic and cause the control logic to fail. Most existing detuning correction methods require real-time amplitude and phase detection to update the control variables, and the control rate needs to be improved. To this end, the present invention proposes a novel detuning correction idea of ​​reactive power negative feedback, which can introduce reactive power by constructing a detuning state in the resonant network. The reactive power in turn corrects the energy negative feedback logic of the detuning state to ensure that the system spontaneously maintains a resonant state. Starting from the phase relationship between active and reactive power, the present invention comprehensively analyzes the system design rules that need to be followed when constructing the negative feedback logic, and designs two prototypes with different impedance characteristics to verify its feasibility for arbitrary impedance networks. Experimental results show that the detuning correction scheme can ensure that the system always maintains a resonant state under severe impedance disturbance without the need for a transition process, which can greatly improve the anti-interference ability of the WPT system.

[0035] The classic structure of the series-series wireless power transfer (SS-WPT) system is as follows: Figure 1 As shown, v fais the high frequency excitation voltage source, C1 and L1 are the transmitting end resonant capacitor and the transmitting end coil respectively, L S With C S are the receiving end coil and the receiving end resonant capacitor, R S1 With R S11 are the lumped resistances of the transmitting and receiving ends respectively, and M is the resistance of L1 and L S According to the mutual inductance theory, the receiving end connects L1 and L S The mutual inductance M between them is equivalent to a real resistance R eq and the imaginary reactance X eq The equivalent impedance Z eq Therefore, the WPT system can still be equivalent to a unilateral resonant network consisting of inductors, capacitors and loads, in which the capacitors realize static energy storage through charge accumulation, while the inductors realize dynamic energy storage through the magnetic field generated by the flow of charges: the resonant current generated by the periodic conversion of dynamic and static energy storage realizes continuous power supply for the load. To facilitate subsequent analysis, the following key voltage, current and power formulas for the SS-WPT system are given:

[0036]

[0037] Where f is v fa The operating frequency, ω is the angular frequency, k is the coupling coefficient between the coils, j is the imaginary unit, P o is the output power. When L1, C1 and X eq The total reactance X in When it is not 0, the excitation voltage source v fa With the input resonant current i z1 The detuned state will deviate from the resonant state, and the power transmission performance of the WPT system will also decrease. The fundamental reason why the detuned state causes the WPT power transmission capacity to decrease is that v fa with i z1 The phase difference between the fa Reactive power periodically transferred between the resonant network: The repeated transfer of the same reactive energy takes up v fa Active power output space.

[0038] To this end, the present invention intends to perform detuning correction by constructing an energy negative feedback loop for reactive power. in For example, when it is perceptual, Figure 2 The logic block diagram of the present invention is given as follows: z1 can be decomposed into fa Zero phase active current i a and hysteresis v fa Reactive current i with a phase of 90° b , if the reactive current i bThe stored energy is picked up and stored, and i b The phase adjustment is a If they are consistent, then we can in The WPT system maintains a resonant state under the premise that it is not 0.

[0039] Specific implementation scheme of energy negative feedback

[0040] The picking up and re-injection of the reactive energy is the core problem to be solved in order to realize the detuning correction idea of ​​the present invention. Figure 3 The WPT topology shown in the figure is used for principle verification. Its reactive power pickup circuit consists of a rectifier capacitor C i2 It is composed of two MOSFET tubes S3 and S4: By properly controlling the phase of S3 and S4, the reactive current i b The stored energy is z1 Then, this part of energy is shaped into the active current i a The current with the same phase is then injected into the resonant network again, thereby achieving detuned state correction.

[0041] To facilitate subsequent theoretical analysis, we first establish Figure 1 and Figure 3 The relationship between key variables. Figure 3 In the example, the DC voltage source V i1 The high-frequency inverter power supply v1 formed by MOSFET tubes S1 and S2 will be used to provide Figure 1 The sinusoidal excitation voltage v shown in fa , where S1 is the first MOSFET tube, S2 is the second MOSFET tube, and the receiving end will use diodes D1~D4 and rectifier capacitor C O The full-bridge rectifier converts the AC voltage into a DC voltage V on the actual load R O The fundamental component v of the square wave voltage high frequency inverter power supply v1 fa , and the equivalent load R L The equivalent relationship between the actual load R can be solved by Fourier transform, and the result is shown in formula (2).

[0042]

[0043] Among them, V fa Yes fa Similarly, C i2 Similarly, the reactive energy will be converted into a DC voltage V i2 , and then construct an AC square wave voltage source v2 in an inverting manner and realize the secondary injection of reactive energy. The fundamental component v of v2 fa2 It can be solved by the following formula:

[0044]

[0045] Among them, V fa2 Yes fa2 The amplitude of is the phase of v2 and v1. Figure 4 S3, S4 and C are given i2 The system logic block diagram for reactive power pickup and secondary injection. The specific logic is as follows:

[0046] 1. In the detuned state, the excitation source v1 and the input current i z1 There is a phase difference between the input and the total reactance X in If it is perceptual, v1 is ahead of i z1 , if it is capacitive, v1 lags behind i z1 .

[0047] 2. According to Euler's formula, i z1 The two currents i with a phase difference of 90° can be a with i b Equivalent substitution. a Zero phase with v1, can be regarded as active current, i b With v1, it is ±90° (with X in properties), can be defined as reactive current.

[0048] 3. By reasonably adjusting the conduction phase of S3 and S4, where S3 is the third MOSFET tube and S4 is the fourth MOSFET tube, the reactive power stored in the reactive current can be extracted: when i b From negative to positive (when i b The flow direction is from left to right, that is, the current i b When the flow direction is from the positive electrode of the excitation voltage source to the negative electrode), S3 is turned on and S4 is turned off, and the energy storage capacitor C i2 Be i b Inject charge; when i b From positive to negative (from right to left, i b From the negative pole of the excitation voltage source to the positive pole), S3 is closed and S4 is turned on, and the charge is stored in C i2 To achieve this goal, for X in In the case of inductive, the phase of S3 and S4 should lag behind v190°, X in When it is capacitive, the phase of S3 and S4 should lead v1 by about 90°.

[0049] 4. The charge accumulation will be at C i2 Similar to v1, v2 will also generate a new current i in the resonant network with a phase within (-90°, 90°) of its own. cSince the phase is no longer ±90°, this means that i c Can be R eq Do work, that is, from i b Part of the absorbed reactive power is converted into active power. c The imaginary part of b To offset, thereby reducing the proportion of reactive power (as described in Article 3, when the phase of S3 and S4 is based on X in When the property is set to 90° or -90°, and by controlling its opening and closing, the system can achieve spontaneous cancellation under the above operating conditions).

[0050] 5, in i b Until it is completely neutralized, it will continue to be C i2 The injected charge leads to c Continue to rise until i c The imaginary part and i b Completely cancel out and achieve detuning correction.

[0051] Therefore, intuitively, by adjusting the phase of S3 and S4, when X in When it is inductive, v2 lags behind v1 by 90°, and when it is capacitive, it leads by 90°, so as to realize negative feedback of reactive power and achieve the purpose of adaptive detuning correction.

[0052] Convergence judgment of energy negative feedback process

[0053] To prove Figure 4 The feasibility of the detuning correction idea shown in the figure is that the present invention will theoretically derive the convergence of the negative feedback process based on intuitive understanding. First, a modal analysis is performed to determine the initial active and reactive currents i a and i b , the flow direction in different modes is as follows Figure 5 As shown in (a)(b)(c)(d) (with X in For example, sensibility).

[0054] Mode 1: S1 and S4 are turned on, S2 and S3 are turned off. In this mode, i a From the voltage source V i1 Extracting energy to power the resonant network, i b Returns its own stored energy to V i1 At the same time, a with i b All are freewheeling through S4, not C i2 Inject charge.

[0055] Mode 2: S1 and S3 are turned on, S2 and S4 are turned off. a Continue from V i1 Extraction of energy, ib Then return mode 1 to V i1 The energy is injected into the resonant network again. a with i b At the same time, C i2 As charge is injected, the stored charge increases.

[0056] Mode 3: S2 and S3 are turned on, S1 and S4 are turned off. b Will continue to be C i2 Injected charge, on the contrary, i a The value in mode 2 will be stored in C in this mode. i2 The charge is extracted and returned to the resonant network. a with i b Both are freewheeling through S2, V i1 Does not participate in the charge exchange process.

[0057] Mode 4: S2 and S4 are turned on, S1 and S3 are turned off. a with i b Free resonance via S2 and S4.

[0058] From the modal analysis, we know that although the initial active current i a Will be related to the reactive current i b Together in mode 2 is C i2 However, this part of energy will return to the resonant network in mode 3 due to the current reversal, that is, the active power will not be injected by S3, S4 and C i2 Therefore, in theoretical analysis, it can be considered that the active current i directly generated by v1 a is a constant value, and only reactive power i is analyzed separately b The convergence of Figure 4 Whether the negative feedback process analyzed is valid.

[0059] For the reactive current i b The convergence process of C i2 The balance relationship between charge injection and extraction is solved. Assuming that the number of cycles of the system operation is n, i bn is the reactive current in the nth cycle, which flows to C i2 The net charge injected is Q n for,

[0060]

[0061] C i2 The total charge accumulated is,

[0062]

[0063] In the nth cycle, the amplitude of v2 is V 2n And the fundamental wave v fa2 The amplitude V fa2n as follows,

[0064]

[0065] Accordingly, the current i generated by v2 in the nth cycle is cn It can be solved by formula (7). Note that i is defined here cn The positive direction is from left to right to ensure that the positive direction is consistent with i z1 Be consistent.

[0066]

[0067] From (7), we can see that i cn It contains real part and imaginary part. Among them, the real part and the initial active current i a In phase, it means that part of the reactive energy passes through i cn The secondary injection is converted into active power; the imaginary part and i bn In the reverse position, the two cancel each other, which means that the reactive power ratio of the resonant network is reduced. At this time, the total active current i of the system in the nth cycle is an It can be expressed by (8), where Re() represents the real part of the complex number.

[0068] i an =i a +Re(i cn ) (8)

[0069] Although I an Produced by v1 and v2, but considering that the system only has v i1 A real voltage source, maintaining i an The required energy can only be provided by v1. Therefore, from the impedance perspective, if v1 is to generate i an When the current is so large, its equivalent input reactance X in the nth cycle is in_n It can be solved by (9), and the result is shown in (10). The imaginary current i in formula (9) is bn Then it can be brought into formula (4) to iterate the next cycle.

[0070]

[0071]

[0072] The iterative process of (4)-(10) requires certain initial conditions. cn The initial value of i c1 Can be regarded as 0, i an with i bnThe initial value of i a1 with i b1 From formula (1), i z1 The solution formula is obtained, and the result is shown in (11). a1 ,i b1 andi c1 After applying formulas (4)-(10), we can achieve i an With X in_n Iterative calculation of .

[0073]

[0074] Figure 6 Different C i2 Next an ,i bn and X in_n The iterative curve can be used to draw the following conclusions:

[0075] 1) The constructed WPT system can converge to a stable state without the need for additional detection and control links. At this time, the reactive current i b With the equivalent input reactance X in_n Will decay to 0, the active current i a will be raised to the resonance state. Figure 4 The explained negative energy feedback characteristics are valid.

[0076] 2) In the energy shaping circuit, C i2 The capacitance value is positively correlated with the convergence speed. i2 =141μF, 47μF and 2μF, V i2 It takes about 3000, 1000 and 44 cycles to reach steady state, which takes about 35ms, 11ms and 0.5ms respectively.

[0077] 3) C i2 The selection only affects the convergence speed, and the coil current i after reaching stability a_s are consistent with the system being in a resonant state, and can be solved by formula (12). It should be noted that R S1 With R S11 It is ignored in the process of approximation, because the proper elimination of smaller parasitic parameters can simplify the calculation formula while ensuring the calculation accuracy, which is a common method in impedance analysis. a_s Also defined as the steady-state resonant current i z1_s , which is to be used in the subsequent analysis with i in formula (1) z1 Make a distinction.

[0078]

[0079] Voltage stress solution under steady-state conditions

[0080] In the previous section, the convergence of the energy negative feedback process was solved to prove the possibility of using this characteristic for adaptive detuning correction. This section focuses on solving S3, S4 and C in the energy pickup loop. i2 The voltage stress at different detuning levels provides a more comprehensive analysis of the electrical performance of the topology.

[0081] Depend on Figure 1 It can be seen from formula (2) and (11) that for an SS-type WPT topology without an energy pickup loop, the active power P in the detuned state is a and reactive power P r It can be solved by the following formula:

[0082]

[0083] Therefore, v fa The ratio of reactive power to active power required Rad ar as follows:

[0084]

[0085] After adding the energy pickup loop, the system will return to the resonant state. At this time, the resonant current i z1 The value of i z1_s It can be solved by formula (12), accordingly, v fa Provided active power P a_s as follows

[0086]

[0087] Among them, I z1_s is the steady-state resonant current i z1_s According to the proportional relationship described by formula (14), vf a1 At output P a_s When there is such a large active power, the reactive power that should be accompanied is as shown in formula (16):

[0088] P r_s =P a_s Rad ar (16)

[0089] P r_s That is, when the system returns to the resonant state, v fa2 The reactive power required for secondary injection is as follows: i2 It only has the functions of switching and energy storage but does not have the ability to generate additional energy. fa2 with i z1_sThe angle between them must be 90° or -90°, so the reactive power that can be injected is as follows:

[0090]

[0091] When the system returns to full resonance, (16) and (17) should be equal to ensure that v fa The reactive power that should be generated is v fa2 Completely canceled. At this time, v fa2 The amplitude V fa2 It can be solved by the following formula:

[0092]

[0093] C i2 The voltage of S3 and S4 is V i2 , can be obtained according to the Fourier transform formula,

[0094]

[0095] Related experiments

[0096] This article is based on Figure 3 The topology shown in the figure designs an experimental platform for principle verification. Coils L1 and L2 are wound in a circular manner, with inner and outer diameters of 9 cm and 16 cm respectively. They adopt a double-layer structure, with each layer containing 12 turns of coils. Ideally, the rated inductance is 144μH, but due to factors such as manufacturing process and coil offset, this value will fluctuate under actual working conditions, which is a common phenomenon of magnetic core coils. This phenomenon also shows that it is difficult to ensure parameter accuracy in the actual working conditions of the WPT system and it is easy to detune. This experiment will give 5 groups of experimental results under different working conditions by changing the value of the resonant capacitor and the degree of coil offset, so as to achieve a comprehensive characteristic analysis.

[0097] Principle verification experiment (±90° condition)

[0098] This experiment is used to verify: X in When it is inductive, v2 should lag behind X in About 90°; X in When it is capacitive, v2 should be ahead of X in During the experiment, C2 = 24nF to ensure quasi-resonance with L2, load 20Ω, coil distance 6cm, and X is controlled by changing C1 in Properties, Example 1: C1 = 35nF, v2 lags v1 by about 90°; Example 2: C1 = 35nF, v2 leads v1 by about 90°; Example 3: C1 = 15nF, v2 leads v1 by about 90°; Example 4: C1 = 15nF, v2 lags v1 by about 90°.

[0099] Table 2

[0100]

[0101]

[0102] Table 2 lists the key experimental results, and the following conclusions can be drawn:

[0103] 1) Figure 4 As shown, the detuning correction logic based on energy negative feedback was successfully verified.

[0104] 2) As shown in Example 1-2, when X in When it is inductive, setting v2 to lag v1 by about 90° can make the system return to v1 and i through energy negative feedback. z1 It is a zero phase resonant state. On the contrary, if the v2 phase setting is wrong, C i2 Unable to pick up reactive power, resulting in V i2 The voltage approaches 0 V. Example 3-4 is the experimental result when Xin is capacitive, and the same conclusion can be obtained.

[0105] 3) Detuning state correction is achieved in both Examples 1 and 3. However, the resonant current I z1 is 2.5A, which is closer to the theoretical value of 2.35A calculated by formula (12). In contrast, the resonant current I in Example 3 is z1 It is only 2A, which is much higher than the 0.85A in the detuned state, but still less than the 2.5A in Example 1. z1 The depression at the crest causes: X in When the resistor is capacitive, S3 and S4 are in a hard switching state, and the switching loss consumes part of the energy that should be transferred to the load, which greatly reduces the power transmission capability and the system efficiency (i z1 It lags behind v2, but considering the positive direction problem, the phase should be compensated by 180°).

[0106] 4) As shown in Example 1-2, when X in When it is inductive, V i2 The experimental value is basically consistent with the calculated value. in When the capacitance is 0, there is a certain error between the theoretical and experimental values, which is also because the hard switching process consumes C i2 is caused by the partial charge.

[0107] WPT systems have higher flexibility and closedness, and have great application potential in harsh environments. However, the detuning problem caused by external interference not only seriously reduces the power transmission capacity and efficiency of the system, but also introduces a very high risk of loss of control. To this end, this paper proposes a detuning correction scheme based on reactive power negative feedback, which can achieve complete decoupling of the resonant state from external factors such as load, distance and parameter accuracy. During the research process, the mechanism of the energy negative feedback process was fully analyzed, and it was put into practice using two additional switching tubes and a storage capacitor, and the influence of the selection of the storage capacitor on the dynamic response capability was analyzed. The experimental part includes a comprehensive verification of the dynamic and steady-state characteristics of this technology. The results show that when the voltage phase design rules analyzed in this paper are met, the system can automatically converge to the resonant state, and can converge to the resonant state within a few milliseconds when the load jumps violently. When the coupling strength continues to fluctuate, the resonant state can be maintained in real time in each cycle. In addition, through comparative experiments, it can be found that the real-time detuning correction can avoid the non-monotonic characteristics of the power curve, the power transmission capacity can be increased by up to 2 times, and the system efficiency can be increased by about 2% at the same output power. The theoretical and experimental results are in good agreement.

[0108] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. Adaptive resonance WPT system based on energy negative feedback, characterized in that: include: Resonant network and reactive power pickup circuit; wherein the resonant network includes a transmitting network and a receiving network; the transmitting network is sequentially connected in series with an excitation power supply, a transmitting end resonant capacitor, a transmitting coil and a transmitting end resistor; The reactive power pickup circuit is connected in series between the excitation power supply and the transmitting end resonant capacitor; The reactive power pickup circuit is composed of a rectifier capacitor, a third MOSFET tube and a fourth MOSFET tube, wherein the third MOSFET tube is connected in series with the rectifier capacitor and then connected in parallel with the fourth MOSFET tube; One end of the transmitting end resonant capacitor is connected between the third MOSFET tube and the fourth MOSFET tube; One end of the excitation power supply is connected between the rectifier capacitor and the fourth MOSFET tube; By adjusting the conduction and phase of the third MOSFET tube and the fourth MOSFET tube, reactive power negative feedback is realized, thereby realizing adaptive resonance of the WPT system; When the reactive current changes from negative to positive, the third MOSFET is turned on and the fourth MOSFET is turned off; when the reactive current changes from positive to negative, the third MOSFET is turned off and the fourth MOSFET is turned on; When the total reactance is inductive, the phase of the third MOSFET tube and the fourth MOSFET tube lags by 90°, and when the total reactance is capacitive, the phase of the third MOSFET tube and the fourth MOSFET tube leads by 90°; The reactive current is the reactive current of the input resonant current in the resonant network, and the total reactance is the total reactance of the equivalent resistance of the resonant capacitor, the transmitting coil, and the mutual inductance between the transmitting network and the receiving network in the resonant network.

2. The system according to claim 1, characterized in that: The excitation power supply includes a first MOSFET tube, a second MOSFET tube and a voltage source. The first MOSFET tube and the voltage source are connected in series and then connected in parallel with the second MOSFET tube. The first MOSFET tube and the second MOSFET tube serve as the positive electrode of the excitation power supply, and the second MOSFET tube and the voltage source serve as the negative electrode of the excitation power supply. The positive electrode of the excitation power supply is connected to one end of the transmitting coil; and the negative electrode of the excitation power supply is connected between the rectifier capacitor and the fourth MOSFET tube.

3. The system according to claim 1, characterized in that: The receiving network includes a receiving coil, a receiving end resistor, a receiving end resonant capacitor, a rectifier circuit, and an actual load, wherein the receiving coil, the receiving end resistor, and the receiving end resonant capacitor are connected in series in sequence, a rectifier circuit is connected in series between the receiving coil and the receiving end resonant capacitor, and the rectifier circuit is connected in parallel with the actual load.

4. The system according to claim 3, characterized in that: The rectifier circuit adopts a full-bridge rectifier circuit.

5. The system according to claim 1, characterized in that: The convergence of the adaptive resonant WPT system is judged through modal analysis and mathematical models.

6. The system according to claim 1, characterized in that: The rectifier capacitor is positively correlated with the time taken for the adaptive resonance to reach stability.

7. The system according to claim 1, characterized in that: The magnitude of the resonant current of the adaptive resonance of the WPT system is the ratio of the excitation source to the sum of the equivalent resistance and the transmitting end resistance.

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