CPT system with secondary side decoupling plate and its pickup end detuning evaluation method

Abstract

The application provides a CPT system with a secondary side decoupling pole plate and a pickup end detuning evaluation method thereof, and the system comprises a direct current power supply, an inverter, a primary side compensation network, a coupling mechanism, a secondary side compensation network, a rectifier, a load and a detection circuit, and is characterized in that the coupling mechanism is a three-port network, wherein: a first pole plate P1 and a second pole plate P2 are connected with an external capacitor C ex1 a third pole plate P3 and a fourth pole plate P4 are connected with an external capacitor C ex2 a fifth pole plate P5 and a sixth pole plate P6 are connected with an external capacitor C ex3 a detection end is connected with a detection circuit. The effect is that the indirect detection of the phase information of the pickup end induced voltage can be realized without affecting the wireless energy transmission, and the detuning degree of the pickup end loop can be evaluated, and the error between the detuning degree evaluation value and the actual value is not more than 1Ω.

Description

Technical Field

[0001] This invention relates to wireless power transfer technology, specifically to a CPT system with a secondary decoupling plate and a method for evaluating the detuning of its pickup end. Background Technology

[0002] Capacitive power transfer (CPT) is a wireless power transfer (WPT) technology that utilizes the electric field between metal plates as the transmission medium. As an important form of WPT technology, CPT systems possess numerous advantages such as miniaturization, light weight, flexible shape, and low eddy current losses. In recent years, researchers have expanded the application scenarios of CPT technology to areas such as bio-implantable devices, consumer electronics, and electric vehicles.

[0003] The ever-expanding application scenarios place higher demands on the stability of wireless power transmission systems. Therefore, the detuning problem of CPT systems urgently needs to be addressed. The main reasons for system detuning are as follows: (1) the primary and secondary side coupling mechanisms are misaligned, leading to changes in the parameters of the coupling mechanism; (2) parameter errors and temperature drift effects of system components. In addition, since the CPT system operates at a high frequency, the imaginary part of the rectifier input impedance cannot be ignored, and the magnitude of this imaginary part changes with the load, which will bring further challenges to the system's resonance stability.

[0004] To ensure that the CPT system can promptly adjust and return to its resonant state when parameters change, it is essential to measure the degree of detuning. When the system's pickup circuit is in resonance, there are various ways to combine directly observable electrical parameters to determine the resonant state of the transmitter circuit. However, for the pickup circuit, since the induced voltage at the pickup end cannot be directly observed, it is impossible to simply determine the circuit's resonant state by measuring the phase difference between the induced voltage and the circuit current. In conclusion, assessing the degree of detuning in the pickup circuit is both a prerequisite and a challenge in determining the resonant state of the CPT system.

[0005] In the existing technology, there is little research on the assessment of the detuning degree of CPT system. Only a few scholars have studied the resonant state of IPT system, but the technical solutions they proposed only determine whether there is detuning, without assessing the degree of detuning. At the same time, some methods are not applicable to CPT system. On the one hand, there is little research on capacitive decoupling coupling mechanism. On the other hand, due to the characteristics of CPT system, the imaginary part of the rectifier input impedance will interfere with the assessment of the detuning degree at the pickup end. Summary of the Invention

[0006] In view of this, the primary objective of this invention is to propose a CPT system with a secondary decoupling plate, which can indirectly measure the system phase information and, considering ideal model errors and measurement errors, can evaluate and correct the degree of detuning of the pickup loop.

[0007] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0008] A CPT system with a secondary-side decoupling plate includes a DC power supply, an inverter, a primary-side compensation network, a coupling mechanism, a secondary-side compensation network, a rectifier, a load, and a detection circuit. The key feature is that the coupling mechanism is a three-port network, wherein an external capacitor C is connected to the first plate P1 and the second plate P2. ex1 The coupling mechanism's transmitting end is connected to the primary-side compensation network, and the third plate P3 and the fourth plate P4 are connected to an external capacitor C. ex2 The coupling mechanism pick-up end is connected to the secondary side compensation network, and the fifth plate P5 and the sixth plate P6 are connected to an external capacitor C. ex3 The detection terminals are formed and connected to the detection circuit. The third electrode plate P3 and the fourth electrode plate P4 are respectively matched with a portion of the first electrode plate P1 and the second electrode plate P2; the fifth electrode plate P5 and the sixth electrode plate P6 are respectively matched with another portion of the first electrode plate P1 and the second electrode plate P2.

[0009] Optionally, the primary-side compensation network adopts an LCL compensation topology, and the secondary-side compensation network adopts a series resonant topology.

[0010] Optionally, the first electrode plate P1 and the second electrode plate P2 are L-shaped and are spliced ​​together at the transmitting end of the coupling mechanism in a complementary manner; the third electrode plate P3 and the fourth electrode plate P4 are rectangular and are symmetrically distributed on both sides of the pickup end of the coupling mechanism, and are corresponding to the main body areas of the first electrode plate P1 and the second electrode plate P2; the fifth electrode plate P5 and the sixth electrode plate P6 are rectangular and are symmetrically distributed in the middle of the pickup end of the coupling mechanism, and are corresponding to the lateral extension areas of the first electrode plate P1 and the second electrode plate P2.

[0011] Optionally, the third electrode plate P3, the fourth electrode plate P4, the fifth electrode plate P5, and the sixth electrode plate P6 are disposed on the same plane.

[0012] Optionally, the detection circuit includes a voltage detection circuit, a current detection circuit, a phase difference detection circuit, and a data correction unit, wherein the voltage detection circuit is used to acquire the detection voltage at the detection terminal, the current detection circuit is used to acquire the loop current at the pickup terminal of the coupling mechanism, the phase difference detection circuit is used to calculate the phase difference between the detection voltage and the loop current, and the data correction unit is used to implement system error correction.

[0013] Optionally, the system errors corrected by the data correction unit include rectifier input impedance error, phase difference between the detection terminal voltage and the pickup terminal induced voltage, and hysteresis error of the sampling circuit.

[0014] Based on the above design, the present invention also provides a method for evaluating the detuning of the pickup end of a CPT system with a secondary-side decoupling plate, the key of which is that it includes the following steps:

[0015] S1: The voltage U3 at the detection port is sampled using a voltage follower to obtain the induced voltage U at the pickup end of the coupling mechanism. 21 Sampled signals with opposite phase It is then converted into a corresponding square wave signal using a zero-crossing comparator.

[0016] S2: Use a current transformer to sample the current I2 in the pickup circuit of the coupling mechanism to obtain the current sampling signal. The signal is further converted into a square wave signal with the same phase by a zero-crossing comparator.

[0017] S3: A phase difference detection circuit is constructed using two D flip-flops, outputting a square wave signal U with a duty cycle of δ. δ Its current square wave signal The rising edge triggers the start and the voltage square wave signal The rising edge triggers the end;

[0018] S4: Identify square wave signal U δ The duty cycle δ, and according to The phase difference between the current I2 at the pickup end of the coupling mechanism and the voltage U3 at the detection end port is obtained.

[0019] S5: Based on phase difference Determine if the pickup circuit is detuned. When the pickup circuit is capacitively detuned, When the pickup circuit is inductively detuned

[0020] Furthermore, the method also includes the following steps:

[0021] S6: Use Advanced Design System simulation software to build a full-bridge rectifier model, perform rectifier input impedance error analysis, and obtain the required input impedance of the full-bridge rectifier. in, This represents the simulated value of the real part of the rectifier input impedance. This is the simulated value of the imaginary part of the input impedance;

[0022] S7: According to Calculate the voltage U3 at the detection port and the induced voltage U at the pickup end of the coupling mechanism. 21 phase difference between in This represents the equivalent impedance between the detection port voltage U3 and the excitation current I1 at the transmitting end of the coupling mechanism;

[0023] S8: According to Calculate the duty cycle error caused by the lag in the sampling circuit, where T is the system operating period and t is the duty cycle. v The lag time of the voltage signal, t i The lag time of the current signal;

[0024] S9: According to Calculate the reactance evaluation value of the pickup end loop of the coupling mechanism, and use the reactance evaluation value of the pickup end loop of the coupling mechanism to evaluate the degree of system detuning.

[0025] Optionally, in step S7, according to Calculate the equivalent impedance between the detection port voltage U3 and the excitation current I1 at the transmitting end of the coupling mechanism, where ω represents the system resonant angular frequency. This represents the mutual capacitance between the transmitter and the receiver. This represents the mutual capacitance between the transmitting and detecting ends. X represents the mutual capacitance between the pickup and detection ends. s Z represents the reactance of the pickup circuit of the coupling mechanism. rec This indicates the input impedance of the rectifier.

[0026] The effects of this invention are:

[0027] This invention proposes a CPT system with a secondary decoupled plate and a method for evaluating the detuning of the pickup end. Its decoupled capacitive coupling mechanism can indirectly detect the phase information of the induced voltage at the pickup end without affecting wireless power transmission, and can evaluate the degree of detuning of the pickup end circuit. When the pickup end circuit is in resonance, the error between the evaluated value and the actual value of the detuning degree does not exceed 1Ω; when the pickup end circuit is inductively detuned and capacitively detuned, the errors between the evaluated value and the actual value are less than 2% and 5%, respectively. Attached Figure Description

[0028] 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.

[0029] Figure 1 This is a circuit diagram of a CPT system with a secondary decoupling plate in a specific embodiment of the present invention;

[0030] Figure 2 The equivalent circuit diagram of the coupling mechanism based on the Z-parameter is shown.

[0031] Figure 3 This is a diagram showing the distribution of the coupling mechanism plates in a specific embodiment;

[0032] Figure 4 The curves show the mutual capacitance values ​​between the ports under different plate offsets;

[0033] Figure 5 This is a schematic diagram of the detection circuit in a specific embodiment;

[0034] Figure 6 A conversion curve for detecting the phase difference relationship between voltage and current;

[0035] Figure 7 The input impedance curve of the rectifier;

[0036] Figure 8 The waveforms are for port voltage U3, pickup current I2, and phase difference duty cycle δ, where, Figure 8 (a) is a waveform diagram of the parameters corresponding to the resonant state of the pickup terminal circuit. Figure 8 (b) is a waveform diagram of the parameters corresponding to the inductive detuning state of the pickup terminal loop. Figure 8 (c) is a waveform diagram of the parameters corresponding to the capacitive detuning state of the pickup terminal circuit;

[0037] Figure 9 The evaluation values ​​of the pickup terminal circuit reactance are given under different detuning conditions. Detailed Implementation

[0038] 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.

[0039] 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.

[0040] like Figure 1As shown, this embodiment provides a CPT system with secondary-side decoupling plates, which includes a DC power supply, an inverter, a primary-side compensation network, a coupling mechanism, a secondary-side compensation network, a rectifier, a load and a detection circuit. Said coupling mechanism is a three-port network, wherein: the first plate P1 and the second plate P1 are connected to an external capacitor C ex1 form the transmitting end of the coupling mechanism and are connected to said primary-side compensation network, and the third plate P3 and the fourth plate P4 are connected to an external capacitor C ex2 form the pick-up end of the coupling mechanism and are connected to said secondary-side compensation network, and the fifth plate P5 and the sixth plate P6 are connected to an external capacitor C ex3 form the detection end and are connected to said detection circuit. Said third plate P3 and said fourth plate P4 are respectively arranged to match a partial area of said first plate P1 and said second plate P2; said fifth plate P5 and said sixth plate P6 are respectively arranged to match another partial area of said first plate P1 and said second plate P2.

[0041] Through Figure 1 it can be seen that the primary-side compensation network adopts an LCL compensation topology, the secondary-side compensation network adopts a series resonance topology, and the detection end is usually kept open; considering that there is a coupling capacitance between every two plates, use C ij to represent (1≤i<j≤6), and the external capacitor C of each port ex1 to C ex3 as a part of the coupling mechanism are sequentially connected in parallel to C 12 , C 34 and C 56 .

[0042] Based on the Z-parameter-based multi-port capacitive coupling mechanism modeling method, the coupling mechanism is modeled, and by using the coupling capacitance parameter C ij , the voltage and current relationship of each port can be obtained as shown in formula (1).

[0043]

[0044] Wherein, and are the port self-capacitances of the transmitting end, the pick-up end and the detection end respectively, and are the mutual capacitances between the ports of "transmitting end - pick-up end", "transmitting end - detection end" and "pick-up end - detection end" respectively. U1, U2 and U3 respectively represent the port voltages of the coupling mechanism, and I1 and I2 respectively represent the loop currents.

[0045] According to formula (1), the equivalent circuit of the coupling mechanism based on Z parameters can be obtained, as shown in Figure 2 , wherein, U 12 is the induced voltage generated by the transmitting end excited by I2, U21 U is the induced voltage generated at the pickup terminal under the excitation of I1. 31 and U 32 These are the induced voltages generated at the detection terminals under the excitation of I1 and I2, respectively, Z. rec This is the input impedance of the rectifier.

[0046] The induced voltage U at the pickup terminal can be obtained from formula (1). 21 for:

[0047]

[0048] The port voltage U3 at the detection end is:

[0049]

[0050] Comparing formulas (2) and (3), it can be found that if it is possible to make Then it can be approximated as:

[0051]

[0052] Therefore, formula (3) can be rewritten as:

[0053]

[0054] Comparing formulas (2) and (5), it can be found that U at this time 21 Both U3 and U4 have the same phase and lag the current I1 by π / 2. Therefore, the induced voltage U at the pickup terminal can be indirectly obtained by detecting the port voltage U3. 21 The phase information is then obtained. Furthermore, the phase relationship between voltage U3 and current I2 is detected to determine the resonant state of the system's pickup terminal. The phase difference between port voltage U3 and loop current I2 is defined as:

[0055]

[0056] Ideally, the input impedance of a rectifier is purely resistive, that is:

[0057]

[0058] Furthermore, by detecting the voltage U across the load terminals... R and current I R The system load R can be obtained in real time. L Size, such as Figure 1 As shown, the pick-up terminal circuit reactance jX can be calculated from this. s for:

[0059]

[0060] Therefore, the degree of detuning at the pickup end of this CPT system can be evaluated through this reactance value.

[0061] To realize port mutual capacitance based on Z-parameter Much larger Therefore, the detection end plate in the coupling mechanism needs to be decoupled from the pickup end plate as much as possible, while ensuring that it is always coupled to the transmitting end plate. To this end, the embodiment proposes a secondary-side decoupling type capacitive coupling mechanism, such as... Figure 3 As shown.

[0062] pass Figure 3 It can be seen that the first electrode plate P1 and the second electrode plate P2 are L-shaped and are spliced ​​together at the transmitting end of the coupling mechanism in a complementary manner. The third electrode plate P3 and the fourth electrode plate P4 are rectangular and are symmetrically distributed on both sides of the pickup end of the coupling mechanism, corresponding to the main body areas of the first electrode plate P1 and the second electrode plate P2. The fifth electrode plate P5 and the sixth electrode plate P6 are rectangular and are symmetrically distributed in the middle of the pickup end of the coupling mechanism, corresponding to the lateral extension areas of the first electrode plate P1 and the second electrode plate P2. Figure 3 (b) It can be seen that the pickup end plates P3 and P4 are two larger square plates, symmetrically placed on both sides of the secondary side; the detection end plates P5 and P6 are composed of two smaller square plates, symmetrically placed in the middle of the secondary side, as shown in the image. Figure 3 As shown in (c). Furthermore, plates P3, P4, P5, and P6 are all located on the same plane, with a spacing of d between adjacent plates, to achieve maximum decoupling between the detection end plate and the pickup end plate. Plates P3 and P5 are directly opposite plate P1, and plates P4 and P6 are directly opposite plate P2, as shown in (c). Figure 3 As shown in (a), when the secondary electrode plate is offset from the primary electrode plate in the x or y direction, the detection electrode plate and the transmitting electrode plate always have an overlapping area. This also indicates that the offset range of the secondary electrode plate is limited by the size of the detection electrode plate. The specific dimensional parameters of the coupling mechanism are shown in Table 1.

[0063] Table 1: Dimensional parameters of the coupling mechanism

[0064]

[0065] A coupled mechanism model was constructed using ANSYS Maxwell, and simulation analysis was performed. The curves showing the change in mutual capacitance between ports with increasing secondary plate offset in different offset directions are shown below. Figure 4 As shown. Among them. Figure 4 (a) represents the offset along the x-axis. Figure 4 (b) represents the offset along the y-axis.

[0066] like Figure 4As shown in (a), when the secondary plate is directly above the primary plate, the mutual capacitance is... When the secondary electrode plate is offset by 20mm along the x-axis, the mutual capacitance changes as follows: It can be seen that the mutual capacitance between the transmitting end plate and the picking end plate... The small change indicates that the energy transferred from the transmitter to the receiver is essentially unaffected within this offset range. Meanwhile, the mutual capacitance value... Much larger Therefore, it can be assumed that the secondary-side pickup plate and the detection plate are always decoupled within this offset range. For example... Figure 4 As shown in (b), when the secondary electrode plate is offset by 20 mm along the y-axis, the mutual capacitance between the ports changes as follows: The same conclusion can be obtained as when there is a deviation in the x-axis direction.

[0067] In summary, the three-port coupling mechanism based on secondary-side decoupling proposed in this embodiment can achieve indirect detection of the phase information of the induced voltage on the pickup side without significantly affecting the system's energy transfer.

[0068] like Figure 5 As shown, to obtain the phase difference between the detection terminal voltage U3 and the pickup terminal loop current I2, the detection circuit includes a voltage detection circuit, a current detection circuit, a phase difference detection circuit, and a data correction unit. The voltage detection circuit is used to acquire the detection voltage at the detection terminal, the current detection circuit is used to acquire the loop current at the pickup terminal of the coupling mechanism, the phase difference detection circuit is used to calculate the phase difference between the detection voltage and the loop current, and the data correction unit is used to implement system error correction.

[0069] First, the voltage follower in the voltage detection circuit samples the detection terminal voltage U3 to obtain the voltage U at the pickup terminal. 21 Sampled signals with opposite phase Then, a zero-crossing comparator is used to convert it into a corresponding square wave signal. Similarly, the current I2 at the pickup terminal is sampled using a current transformer to obtain a current sampling signal. The signal is further converted into a square wave signal with the same phase by a zero-crossing comparator. The phase relationship transformation of each voltage and current signal is as follows: Figure 6 As shown.

[0070] The phase difference detection circuit consists of two D flip-flops, which output a square wave signal U with a duty cycle of δ. δ Its current square wave signal The rising edge triggers the start and the voltage square wave signal The rising edge of the signal triggers the termination, therefore the phase relationship between the loop current I2 and the port voltage U3 can be determined from the duty cycle δ of the square wave signal. Figure 6 It can be seen that, under ideal conditions, if the loop current I2 is in phase with the port voltage U3, that is, the pickup loop is in resonance, then the duty cycle δ = 50%; if the loop current I2 leads the port voltage U3, that is, the pickup loop is capacitively detuned, then δ > 50%; if the loop current I2 lags the port voltage U3, that is, the pickup loop is inductively detuned, then δ < 50%.

[0071] Therefore, the phase difference between the loop current I2 and the port voltage U3 can be derived. for:

[0072]

[0073] When the pickup circuit is capacitively detuned When the pickup circuit is inductively detuned

[0074] To ensure that the detection and evaluation results more closely approximate the actual system operation, the errors between the system in actual operation and the ideal situation need to be considered. The system errors corrected by the data correction unit include rectifier input impedance error, phase difference between the detection terminal voltage and the pickup terminal induced voltage, and hysteresis error of the sampling circuit. A detailed analysis follows:

[0075] 1) Rectifier input impedance error:

[0076] Since the system operates at a high frequency, the input impedance of the full-bridge rectifier is no longer a pure resistance, and its imaginary part can no longer be ignored and its magnitude is affected by the diode parameters, load resistance, and DC side voltage of the rectifier.

[0077] Using the Advanced Design System simulation software, a full-bridge rectifier model based on the SiC diode SCS310 was built, and a load R was applied. L For 50Ω~100Ω, DC side voltage U R Simulations were performed under conditions of 10–50V to obtain the real and imaginary parts of the rectifier input impedance, as follows: Figure 7 As shown, Figure 7 (a) represents the real part value. Figure 7 (b) represents the imaginary part. Simulation results show that at an operating frequency of 500kHz, the imaginary and real parts of the full-bridge rectifier are of the same order of magnitude, and the real part also has an error compared to the theoretically calculated value. Therefore, under high-frequency conditions, the input impedance of this full-bridge rectifier should be:

[0078]

[0079] in, This represents the simulated value of the real part of the rectifier input impedance. This is the simulated value of the imaginary part of the input impedance.

[0080] 2) Voltages U3 and U 21 Phase error:

[0081] From formula (3), it can be seen that the port voltage U3 and the induced voltage U 21 There is a phase difference between them, and this error is affected by the pickup current I2.

[0082] According to Kirchhoff's laws and formula (2), the pickup current I2 can be obtained as:

[0083]

[0084] Substituting formulas (8) and (11) into formula (3), we get:

[0085]

[0086] Define the equivalent impedance I1 between the port voltage U3 and the current as:

[0087]

[0088] Comparing formulas (2) and (12), we can obtain the relationship between the port voltage U3 and the induced voltage U. 21 phase difference between for:

[0089]

[0090] From formulas (13) and (14), it can be seen that the port voltage U3 and the induced voltage U 21 phase difference between Through Z rec Simulation values ​​and jX s The measured values ​​are calculated to obtain jX s Perform iterative correction.

[0091] 3) Sampling circuit lag:

[0092] like Figure 6 As shown, the detection terminal voltage U3 is sampled and converted into a square wave signal. Afterwards, the signal lags behind the original signal at the zero-crossing point, and this lag time conforms to the typical value in the detection circuit device manual. Let the lag time of the voltage signal be t. v Similarly, the pickup current I2 also lags behind the square wave signal. Let the lag time of the current signal be t. iHowever, due to differences in sampling methods and the devices used, the sampling lag times for voltage and current are also different. Let's assume that this results in a lag time for the square wave signal U. δ If the resulting duty cycle error is Δδ, then:

[0093]

[0094] Where T is the system operating cycle.

[0095] To correct the above errors, after receiving the duty cycle signal representing the phase difference from the detection circuit, the processor must first compensate for the error Δδ; then, it must adjust the voltage U across the load. R Current I R The load value is detected to determine the current load value, which is then compared with the pre-stored rectifier input impedance simulation value database in the processor to obtain the corresponding impedance value, thereby calculating the phase difference between the current voltage and current. Finally, the simulated value of the rectifier input impedance is used to calculate the evaluation value jX of the pickup terminal circuit reactance. * .

[0096] In summary, after correction, the pickup terminal circuit reactance jX * for:

[0097]

[0098] Therefore, this embodiment can be summarized into a method for evaluating the pick-up end detuning of a CPT system with a secondary-side decoupling plate, including the following steps:

[0099] S1: The voltage U3 at the detection port is sampled using a voltage follower to obtain the induced voltage U at the pickup end of the coupling mechanism. 21 Sampled signals with opposite phase It is then converted into a corresponding square wave signal using a zero-crossing comparator.

[0100] S2: Use a current transformer to sample the current I2 in the pickup circuit of the coupling mechanism to obtain the current sampling signal. The signal is further converted into a square wave signal with the same phase by a zero-crossing comparator.

[0101] S3: A phase difference detection circuit is constructed using two D flip-flops, outputting a square wave signal U with a duty cycle of δ. δ Its current square wave signal The rising edge triggers the start and the voltage square wave signal The rising edge triggers the end;

[0102] S4: Identify square wave signal U δ The duty cycle δ, and according to The phase difference between the current I2 at the pickup end of the coupling mechanism and the voltage U3 at the detection end port is obtained.

[0103] S5: Based on phase difference Determine if the pickup circuit is detuned. When the pickup circuit is capacitively detuned, When the pickup circuit is inductively detuned

[0104] To further determine the degree of detuning, the above method may also include the following steps:

[0105] S6: Use Advanced Design System simulation software to build a full-bridge rectifier model, perform rectifier input impedance error analysis, and obtain the required input impedance of the full-bridge rectifier. in, This represents the simulated value of the real part of the rectifier input impedance. This is the simulated value of the imaginary part of the input impedance;

[0106] S7: According to Calculate the voltage U3 at the detection port and the induced voltage U at the pickup end of the coupling mechanism. 21 phase difference between in This represents the equivalent impedance between the detection port voltage U3 and the excitation current I1 at the transmitting end of the coupling mechanism, and is calculated according to:

[0107] calculate;

[0108] S8: According to Calculate the duty cycle error caused by the lag in the sampling circuit, where T is the system operating period and t is the duty cycle. v The lag time of the voltage signal, t i The lag time of the current signal;

[0109] S9: According to Calculate the reactance evaluation value of the pickup end loop of the coupling mechanism, and use the reactance evaluation value of the pickup end loop of the coupling mechanism to evaluate the degree of system detuning.

[0110] To further verify the effectiveness of this invention, a CPT system prototype constructed using the proposed coupling mechanism was tested. Copper foil printed on a PCB was used as the electrode plate of the coupling mechanism, ensuring that electrodes on the same side remained on the same plane. A high-voltage ceramic capacitor was used as the external capacitor C for both the transmitter and receiver. ex1 C ex2 The external capacitor C at the detection end ex3The system consists of a series-parallel array of thin-film capacitors to divide the port voltage U3, achieving the input voltage range of the detection circuit. The compensation capacitor C1 is also composed of a group of thin-film capacitors. The compensation inductor is constructed by winding Litz wire around a high-frequency silicon iron core. The high-frequency core helps increase the inductor's power density and reduce the amount of Litz wire used, thus reducing the size of the compensation inductor. It also reduces electromagnetic radiation and parameter sensitivity. The system parameter values ​​are shown in Table 2.

[0111] Table 2: Circuit parameters of the system prototype

[0112]

[0113] A 500kHz PWM control signal is generated by the DSP to control the inverter. The inverter MOSFET is model C2M0080120D, and the rectifier SiC diode is model SCS310. The load is a sliding rheostat, which facilitates the adjustment of different load values.

[0114] In the detection circuit, the voltage follower uses an OPA2810 dual-supply, rail-to-rail operational amplifier; the current Hall element uses an intrusive current transformer PA1005; the comparator in the zero-crossing comparator circuit is a TLV3501; and the D flip-flop used for phase difference detection is a 74AC11074; finally, the detection data is processed using an STM32F403 controller.

[0115] Regarding the detection and verification of phase difference:

[0116] When the system operating frequency is 500kHz, the load R L =70Ω, voltage U across the load R At 30V, the waveforms of the port voltage U3, loop current I2, and phase difference duty cycle δ were measured under three conditions: resonance, inductive detuning, and capacitive detuning at the pickup terminal, as shown below. Figure 8 As shown. Where α is the phase difference between the current I2 and the inverted signal of the detection terminal voltage U3, i.e.

[0117] like Figure 8 As shown in (a), when the pickup circuit resonates, α = -193.8° is measured, which is the actual phase difference between current I2 and voltage U3. At the same time, the detection circuit measures the square wave signal U δ The duty cycle δ is 53.63%. From formula (9), the calculated phase difference between current I2 and voltage U3 is: The error is 0.73°. Similarly, the voltage and current phase conditions of the pickup circuit under inductive and capacitive detuning are as follows: Figure 8 (b) and Figure 8 As shown in (c), α was measured to be -161.6° and -218.6°, respectively. From this, the actual phase difference between the current and voltage can be obtained. The phase differences are 18.4° and -38.6°, respectively. The detection circuit measured the phase difference duty cycles δ to be 44.69% and 60.52%, respectively, from which the calculated phase differences of the current and voltage can be derived. The values ​​are 19.12° and -37.87°, respectively, with errors of 0.72° and 0.73°.

[0118] Therefore, it can be proven that under the conditions of pickup circuit resonance, inductive detuning, and capacitive detuning, the phase difference between pickup current I2 and port voltage U3 can be calculated relatively accurately using the duty cycle δ measured by the detection circuit.

[0119] System mistuning assessment:

[0120] According to formula (16), the evaluation value of the pickup terminal loop reactance is calculated using the STM32 controller. Under load voltage U R The load R is calculated for 10V, 30V, and 50V respectively. L The calculated evaluation value jX of the pickup terminal circuit reactance in the range of 50Ω to 100Ω. * like Figure 9 As shown.

[0121] Figure 9 In the diagram, the solid lines represent the actual reactance values ​​of the pickup circuit, which are 0Ω, 32.58Ω, and -30.99Ω, respectively. When the pickup circuit resonates, i.e., the actual reactance of the circuit is 0Ω, the calculated evaluation values ​​under different load values ​​and different load voltages are as follows: Figure 9 The numbers above the solid 0Ω line represent the resistance. It can be seen that the maximum error in the assessed value is 0.94Ω, and the minimum is 0.09Ω. When the pickup circuit is inductively detuned, i.e., the actual value of the circuit reactance is 32.58Ω, the error between the assessed and actual reactance values ​​is expressed as a percentage. It can be seen that the maximum error is -1.76%, and the minimum is -0.1%. When the pickup circuit is capacitively detuned, i.e., the actual value of the circuit reactance is -30.99Ω, the maximum error between the assessed and actual reactance values ​​is 4.45%, and the minimum is 0.35%.

[0122] Experiments show that the pickup-end circuit reactance evaluation method proposed in this invention can calculate the circuit reactance value under different detuning conditions, and achieve accurate evaluation of the degree of detuning of the pickup-end circuit.

[0123] In summary, this invention proposes a CPT system with a secondary-side decoupling plate and a method for evaluating pickup detuning. Based on Z-parameters, a mathematical model and equivalent circuit of the multi-port capacitive coupling mechanism are established. Coupling conditions for indirect measurement of induced voltage and an evaluation model for the degree of pickup detuning are presented. Based on the coupling conditions, a secondary-side decoupling capacitive coupling mechanism is proposed, and a detection circuit is designed based on this mechanism. Considering ideal model errors and measurement errors, a method for evaluating and correcting the degree of detuning is proposed.

[0124] Experimental results demonstrate that the decoupled capacitive coupling mechanism proposed in this invention can indirectly detect the phase information of the induced voltage at the pickup end without affecting wireless power transmission. It also assesses the degree of detuning in the pickup end circuit, achieving an error of no more than 1Ω between the assessed and actual values ​​when the pickup end circuit is in resonance; and less than 2% and 5% when the pickup end circuit is inductively or capacitively detuned, respectively.

[0125] 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 CPT system with a secondary-side decoupling plate, comprising a DC power supply, an inverter, a primary-side compensation network, a coupling mechanism, a secondary-side compensation network, a rectifier, a load, and a detection circuit, characterized in that, The coupling mechanism is a three-port network, wherein: the first plate P1 and the second plate P2 are connected to an external capacitor C. ex1 The coupling mechanism's transmitting end is connected to the primary-side compensation network, and the third plate P3 and the fourth plate P4 are connected to an external capacitor C. ex2 The coupling mechanism pick-up end is connected to the secondary side compensation network, and the fifth plate P5 and the sixth plate P6 are connected to an external capacitor C. ex3 The detection terminals are formed and connected to the detection circuit. The third electrode plate P3 and the fourth electrode plate P4 are respectively matched with a portion of the first electrode plate P1 and the second electrode plate P2; the fifth electrode plate P5 and the sixth electrode plate P6 are respectively matched with another portion of the first electrode plate P1 and the second electrode plate P2. The pickup end performs a detuning assessment according to the following steps: S1: The voltage U3 at the detection port is sampled using a voltage follower to obtain the induced voltage U at the pickup end of the coupling mechanism. 21 Sampled signals with opposite phase It is then converted into a corresponding square wave signal using a zero-crossing comparator. ; S2: Use a current transformer to sample the current I2 in the pickup circuit of the coupling mechanism to obtain the current sampling signal. It is further converted into a square wave signal with the same phase by a zero-crossing comparator. ; S3: A phase difference detection circuit is constructed using two D flip-flops, outputting a square wave signal U with a duty cycle of δ. δ Its current square wave signal The rising edge triggers the start and the voltage square wave signal The rising edge triggers the end; S4: Identify square wave signal U δ The duty cycle δ, and according to The phase difference between the current I2 at the pickup end of the coupling mechanism and the voltage U3 at the detection end port is obtained. ; S5: Based on phase difference Determine if the pickup circuit is detuned. When the pickup circuit is capacitively detuned, When the pickup circuit is inductively detuned, ; S6: Use Advanced Design System simulation software to build a full-bridge rectifier model, perform rectifier input impedance error analysis, and obtain the required input impedance of the full-bridge rectifier. ,in, This represents the simulated value of the real part of the rectifier input impedance. This is the simulated value of the imaginary part of the input impedance; S7: According to Calculate the voltage U3 at the detection port and the induced voltage U at the pickup end of the coupling mechanism. 21 phase difference between ,in This represents the equivalent impedance between the detection port voltage U3 and the excitation current I1 at the transmitting end of the coupling mechanism; S8: According to Calculate the duty cycle error caused by the lag in the sampling circuit, where T is the system operating period and t is the duty cycle. v The lag time of the voltage signal, t i The lag time of the current signal; S9: According to Calculate the reactance evaluation value of the pickup end loop of the coupling mechanism, and use the reactance evaluation value of the pickup end loop of the coupling mechanism to evaluate the degree of system detuning.

2. The CPT system with a secondary-side decoupling plate according to claim 1, characterized in that: The primary-side compensation network adopts an LCL compensation topology, and the secondary-side compensation network adopts a series resonant topology.

3. The CPT system with a secondary-side decoupling plate according to claim 1 or 2, characterized in that: The first electrode plate P1 and the second electrode plate P2 are L-shaped and are spliced ​​together at the transmitting end of the coupling mechanism in a complementary manner; the third electrode plate P3 and the fourth electrode plate P4 are rectangular and are symmetrically distributed on both sides of the pickup end of the coupling mechanism, and are set corresponding to the main body area of ​​the first electrode plate P1 and the second electrode plate P2; the fifth electrode plate P5 and the sixth electrode plate P6 are rectangular and are symmetrically distributed in the middle of the pickup end of the coupling mechanism, and are set corresponding to the lateral extension area of ​​the first electrode plate P1 and the second electrode plate P2.

4. The CPT system with a secondary-side decoupling plate according to claim 3, characterized in that: The third electrode plate P3, the fourth electrode plate P4, the fifth electrode plate P5, and the sixth electrode plate P6 are disposed on the same plane.

5. The CPT system with a secondary-side decoupling plate according to claim 1, 2, or 4, characterized in that: The detection circuit includes a voltage detection circuit, a current detection circuit, a phase difference detection circuit, and a data correction unit. The voltage detection circuit is used to acquire the detection voltage at the detection end, the current detection circuit is used to acquire the loop current at the pickup end of the coupling mechanism, the phase difference detection circuit is used to calculate the phase difference between the detection voltage and the loop current, and the data correction unit is used to implement system error correction.

6. The CPT system with a secondary-side decoupling plate according to claim 5, characterized in that: The system errors corrected by the data correction unit include rectifier input impedance error, phase difference between the detection terminal voltage and the pickup terminal induced voltage, and hysteresis error of the sampling circuit.

7. The CPT system with a secondary-side decoupling plate according to claim 1, characterized in that: In step S7, according to Calculate the equivalent impedance between the detection port voltage U3 and the excitation current I1 at the transmitting end of the coupling mechanism, where Indicates the system's resonant angular frequency. This represents the mutual capacitance between the transmitter and the receiver. This represents the mutual capacitance between the transmitting and detecting ends. This represents the mutual capacitance between the pickup and detection ends. Indicates the reactance of the pickup circuit at the coupling mechanism. This indicates the input impedance of the rectifier.

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