A switched capacitor compensation control method for a dual-load wireless power transfer system

Abstract

This invention discloses a switched-capacitor compensation control method for a dual-load wireless power transfer system, achieving optimized wireless power transfer efficiency under various operating conditions. Based on the load state and mutual inductance coefficient under different conditions, the secondary-side compensation switched-capacitor and the primary-side LCC structure switched-capacitor are synchronously controlled by detecting the dual-load current. This allows the dual loads to achieve the target output power while reducing the input impedance angle, thereby improving the overall system transmission efficiency. The system transmission efficiency curves under different load power distributions are analyzed to achieve the optimal power distribution requirement for transmission efficiency. The size of the switched-capacitor can be adjusted by collecting the input voltage and load current of each converter. The process is simple and significantly improves power transfer and efficiency optimization. The same method can also achieve constant current control, and the system parameters are easy to set, exhibiting good economic efficiency and practicality.

Description

Technical Field

[0001] This invention relates to the field of wireless power transmission, and in particular to a switched capacitor compensation control method for a dual-load wireless power transmission system. Background Technology

[0002] Compared to traditional wired charging, wireless charging technology offers advantages such as charging safety, timeliness, and convenience. Currently, electric vehicle charging using magnetically coupled resonant technology achieves a charging efficiency of 85%–90% and employs a single-load system. However, single-load systems also have some drawbacks: firstly, the single load results in lower overall system utilization; secondly, location is limited, requiring the receiving and transmitting coils to be coaxial to achieve maximum transmission efficiency.

[0003] Existing technologies have only achieved power distribution without considering magnetic coupling between secondary coils, without further research on the existence of cross coupling on the secondary side. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application proposes a switched-capacitor compensation control strategy for a dual-load wireless power transfer system under cross-coupling effects. This strategy enhances anti-offset capability while enabling flexible power allocation for wireless charging of new energy vehicle batteries, thereby improving the system's power transfer capacity. The one-to-two wireless power transfer system full-resonant control technology is a new technology derived from wireless power transfer technology, primarily applied to electric vehicles. It enables one charging station to simultaneously power two new energy vehicles. Dual-load wireless charging technology, based on vertical charging stations, allows for bi-directional wireless charging for new energy vehicles with rear-mounted wireless charging, reducing the number of charging stations required and lowering construction costs. It also provides users with a better charging experience, achieving a win-win situation for both the State Grid and new energy vehicle users.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A switched capacitor compensation control method for a dual-load wireless power transfer system includes the following steps:

[0007] Step 1: Construct the circuit topology diagram of the three-coil wireless power transmission system;

[0008] Step 2: Obtain the output voltage U of the DC power supply. dc1 It is then output to the primary-side high-frequency inverter module, which outputs an 80kHz AC square wave to the primary-side coil.

[0009] Step 3: Calculate the load impedance value using the voltage and current of the secondary load;

[0010] Step 4: Given the desired output power of the two secondary sides, construct the control equations for the charging current of the load battery;

[0011] Step 5: Improve the overall system efficiency by controlling the primary-side switching capacitor C1.

[0012] As a further technical solution of the present invention: step 1 specifically includes:

[0013] Step 1.1: Construct the circuit topology of the dual-load wireless power transmission system. The circuit topology specifically includes: DC power supply (1), primary-side high-frequency inverter module (2), transmitting coil module (3), receiving coil module (4), secondary-side rectifier module (5), battery load (6), primary-side switched capacitor (7), secondary-side 1 switched capacitor (8), and secondary-side 2 switched capacitor (9).

[0014] Among them, the DC power supply (1) is connected to the input terminal of the primary side high-frequency inverter module (2), the output terminal of the high-frequency inverter (2) is connected to the input terminal of the transmitting coil module (3), the output terminal of the transmitting coil module (3) is set opposite to the input terminal of the receiving coil module (4), the output terminal of the receiving coil module (4) is connected to the input terminal of the secondary side rectifier module (5), the output terminal of the secondary side rectifier module (5) is connected to the system battery load (6), the primary side switching capacitor (7) is connected in series in the primary side LCC topology, and the secondary side 1 switching capacitor (8) and the secondary side 2 switching capacitor (9) are connected in series in the secondary side topology as compensation capacitors;

[0015] Step 1.2: Control the primary side DC power supply (1) to obtain a suitable output voltage, obtain a high-frequency voltage with zero phase through the high-frequency inverter (2), pass through the topology compensation coil structure to the transmitting coil module (3) to output to the receiving coil module (4) input voltage, the secondary side rectifier module (5) converts the high-frequency AC power to DC power, the secondary side battery load (6) is connected to the output of the secondary side rectifier module (5) to absorb power;

[0016] Step 1.3: The primary-side switched capacitor (7), secondary-side 1 switched capacitor (8), and secondary-side 2 switched capacitor (9) serve as compensation capacitors for the transmitting coil module (3) and the receiving coil module (4). By controlling the first switching transistor S in the primary-side switched capacitor (7), secondary-side 1 switched capacitor (8), and secondary-side 2 switched capacitor (9), x and the second switching transistor S yBy maintaining the on / off state with a certain duty cycle, the equivalent capacitance of the primary-side switching capacitor (7), secondary-side 1 switching capacitor (8), and secondary-side 2 switching capacitor (9) is changed to obtain a suitable capacitance value. The capacitance values ​​of the secondary-side 1 switching capacitor (8) and secondary-side 2 switching capacitor (9) are changed to obtain the target output current. The capacitance value of the primary-side switching capacitor (7) is changed to change the reactive power of the one-to-two wireless power transmission system.

[0017] Step 1.4: Determine the equivalent circuit of the one-to-two wireless power transmission system. Based on Kirchhoff's voltage and current laws, obtain a set of equations relating the input impedance and the relationship between the output power and the magnitude and phase of the voltage.

[0018] As a further technical solution of the present invention: step 2 specifically includes:

[0019] Step 2.1: Control the first switching transistor S in the primary-side switching capacitor (7), secondary-side 1 switching capacitor (8), and secondary-side 2 switching capacitor (9). x and the second switching transistor S y Maintain the on / off state with a certain duty cycle, turn on the voltage source and determine that the system is working normally;

[0020] Step 2.2: Obtain the output voltage U of the DC power supply (1) dc1 and output current I dc1 After passing through a high-frequency inverter, an AC square wave is obtained with an amplitude of U. dc1 The phase is considered to be zero. According to Fourier decomposition, the voltage can be decomposed as follows:

[0021] (k is an odd number, ω is the angular frequency);

[0022] Step 2.3: The acquired high-frequency voltage passes through the LCC resonant topology compensation circuit and reaches the transmitting coil. By Kirchhoff's voltage theorem, the following specific equation is obtained;

[0023]

[0024] Another L p C p Resonance, the resonant frequency is:

[0025]

[0026] Simplifying the above formula, the output current to the primary-side transmitting coil is:

[0027] I1=-jωC p U in

[0028] In the above formula, L pThe compensating inductor of the resonant topology; C p The parallel compensation capacitor represents the resonant topology; U in U ac1 The fundamental component; I in Input current I ac1 fundamental wave component.

[0029] As a further technical solution of the present invention: step 3 specifically includes:

[0030] Step 3.1: Select a suitable power supply voltage U in Parallel compensation capacitor C of the resonant topology p A suitable output current I1 is obtained for the primary-side transmitting coil;

[0031] Step 3.2: The two secondary receiving coil modules obtain a suitable current through the primary transmitting coil. However, there is also mutual inductance between the two secondary receiving coils, and the currents of the three coils are coupled. The specific current equations for the two secondary windings are as follows:

[0032] a=jωM 12

[0033] b=jωM 13

[0034]

[0035] e=jωM 23

[0036] By applying Kirchhoff's voltage theorem, the current flowing from the output to the two secondary transmitting coils is:

[0037]

[0038] Where C2 represents the series compensation capacitor of the resonant topology of secondary coil 2, i.e., the switching capacitor of secondary coil 1 (8); R2 represents the parasitic resistance of secondary coil 2; R eq2 C3 represents the series compensation capacitor of the resonant topology of the secondary coil 3, i.e., the switching capacitor of the secondary coil 2 (9); R3 represents the parasitic resistance of the secondary coil 3; R eq3 I2 represents the current flowing through the secondary coil 2, and I3 represents the current flowing through the secondary coil 3; M 12 M represents the mutual inductance between coils 1 and 2. 13 This represents the mutual inductance between coils 1 and 3. Because the two secondary coils are relatively close, the mutual inductance M between the two secondary coils is considered. 23 .

[0039] As a further technical solution of the present invention: step 4 specifically includes:

[0040] Step 4.1: When the battery load impedance and mutual inductance of each side are not adjustable, the method of controlling the current by changing the series compensation capacitors C2 and C3 of the resonant topology of the secondary coil 2 has been given in step 3.2:

[0041] I2 = f(C2, C3)

[0042] i3 = H(C2, C3)

[0043] The equations for C2 and C3 with respect to I2 and I3 are solved using an iterative method:

[0044]

[0045] Step 4.2: By controlling the first switching transistor S in the primary-side switching capacitor (7), secondary-side 1 switching capacitor (8), and secondary-side 2 switching capacitor (9) x and the second switching transistor S y The capacitance equation is as follows: Maintaining the on / off state with a certain duty cycle, the capacitance value is calculated as follows:

[0046]

[0047] Among them, C eq C represents the total capacitance of the switched capacitors. a For a fixed capacitor, C b For a series capacitor, β is the switching angle;

[0048] Step 4.3: Control the magnitudes of the secondary coil currents i2 and i3 to change the power distribution between load battery 2 and load battery 3. The specific power calculation is as follows:

[0049] P out2 =I2 2 R eq2

[0050] P out3 =I3 2 R eq3

[0051] In the above formula, P out1 P represents the amount of power received by battery load 1. out2 This indicates the amount of power received by battery load 2.

[0052] As a further technical solution of the present invention: step 5 specifically includes:

[0053] Step 5.1: When the output power remains constant, the overall efficiency of the system is related to the input power. For the input impedance, assume U... in If the phase is zero, then the following equation holds:

[0054] Pin =U in I in cosΦ

[0055]

[0056] P cu =I in 2 Z in cosΦ=I in 2 R in

[0057]

[0058] Where P cu For system losses, Z in It is the input impedance, R in The input resistance is η, cosΦ is the power factor, and η% is the system efficiency.

[0059] Step 5.2: The power factor is maximized, at which point the system efficiency is highest; U in If the phase is zero, then the first switch S of the primary-side switching capacitor (7) is controlled. x1 and the second switching transistor S y1 Maintaining the on / off state with a certain duty cycle, changing the value of C1, so that I in Since the imaginary part is zero, according to Kirchhoff's voltage theorem, the primary input current can be solved as follows:

[0060]

[0061] From the above formula, we obtain the vector expression:

[0062] I in =I′ in +I c1

[0063] Among them, I' in With fixed magnitude and phase, I C1 It is a purely imaginary number, and its size is adjustable. in There exists a minimum value, at which point I... in with I C1 Perpendicular to U in Vertical, so that the input reactive power is zero;

[0064] From the vector expression, the topology loop vector diagram when C1 is not controlled is obtained, as follows: Figure 16 As shown;

[0065] By controlling the value of C1 to maximize the power factor angle, the specific equation is as follows:

[0066]

[0067] The topology vector diagram when the power factor angle is maximum is obtained as follows: Figure 17 As shown; the relationships between the vectors are derived from the vector graph, and I is then analyzed through C1. in Phase adjustment achieves maximum system efficiency.

[0068] As a further technical solution of the present invention: During the operation of the system, the state of the battery changes continuously with the degree of charging. In order to charge the battery with a certain appropriate power, constant current charging is adopted. The charging battery is controlled only by current to stabilize the output current. The current magnitude of the secondary side of the charging battery is collected by the signal acquisition and transmission module and compared with the rated charging current. Through PID control, excitation pulses are given to the three switching capacitors at the corresponding trigger angles to control the magnitude of the output current.

[0069] As a further technical solution of the present invention: the setting of the power of the rechargeable battery requires the acquisition of the equivalent load voltage drop on the battery, that is, the product of the equivalent load voltage drop and the current. After comparing it with the ideal receiving power, the desired input power is obtained. That is, the output voltage is obtained by detecting the load voltage drop of the secondary rectifier bridge, and the receiving power of the system is obtained by acquiring the current of the receiving coil circuit. The ideal input power can be obtained by adjusting the excitation pulse of the switching capacitor.

[0070] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0071] This invention provides a one-to-two wireless power transfer method under cross-coupling effect, and proposes a topology and parameter configuration method for dual wireless charging under cross-coupling effect, which realizes the control of charging current and the transmission and distribution of different power between batteries, saving the cost of charging piles. Attached Figure Description

[0072] Figure 1 This is a system topology diagram of the present invention;

[0073] Figure 2 The equivalent load R of the present invention L2 15Ω, R L3 When the impedance is 20Ω, the secondary side 1 power distribution is 4451W.

[0074] Figure 3 The equivalent load R of the present invention L2 15Ω, R L3 When the Ω is 20Ω, the secondary side 2 power distribution is 1853W transmission diagram;

[0075] Figure 4 The equivalent load R of the present inventionL2 15Ω, R L3 Power transfer diagram of primary side when power is distributed at 20Ω;

[0076] Figure 5 The equivalent load R of the present invention L2 20Ω, R L3 Power transfer diagram on the secondary side when the resistance is 25Ω;

[0077] Figure 6 The equivalent load R of the present invention L2 20Ω, R L3 Power transfer diagram on the secondary side when the Ω is 25Ω.

[0078] Figure 7 For the equivalent load R L2 20Ω, R L3 The primary-side power transfer diagram when the Ω is 25Ω.

[0079] Figure 8 For the equivalent load R L2 It is 18Ω, R L3 Power transfer diagram on secondary side 1 when the Ω is 22Ω.

[0080] Figure 9 For the equivalent load R L2 It is 18Ω, R L3 Power transfer diagram on the secondary side when the Ω is 22Ω.

[0081] Figure 10 For the equivalent load R L2 It is 18Ω, R L3 The primary-side power transfer diagram when the Ω is 22Ω.

[0082] Figure 11 This is a comparison of the power transmission in two simulations.

[0083] Figure 12 This is a comparison chart showing the adjustment of each variable in the two simulations.

[0084] Figure 13 This is the flowchart for secondary current control.

[0085] Figure 14 This is the control diagram for the secondary-side C2 and C3 switched capacitors.

[0086] Figure 15 This is the control diagram for the primary-side C1 switched capacitor.

[0087] Figure 16 This is the topology loop vector diagram when C1 is not controlled.

[0088] Figure 17 This is the topology loop vector diagram when the power factor angle is at its maximum.

[0089] Figure 18 Surface diagrams of I2, I3, and C2;

[0090] Figure 19 Surface diagrams of I2, I3, and C3;

[0091] Figure 20 The surface plot of C1 with respect to different values ​​of C2 and C3.

[0092] Figure 21 The graph shows the relationship between system efficiency and I2 and I3.

[0093] Figure 1 In the middle: 1-DC power supply, 2-primary high-frequency inverter module, 3-transmitting coil module, 4-receiving coil module, 5-secondary rectifier module, 6-battery load, 7-primary switching capacitor, 8-secondary 1 switching capacitor, 9-secondary 2 switching capacitor. Detailed Implementation

[0094] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0095] like Figure 1-21 As shown, a switched capacitor compensation control strategy for a dual-load wireless power transfer system based on variable load is disclosed. The method specifically includes the following steps:

[0096] Step 1: Construct the circuit topology diagram of the three-coil wireless power transmission system;

[0097] refer to Figure 1 The circuit topology diagram shown is for a dual-load wireless power transmission system considering cross-coupling effects. The circuit topology specifically includes: DC power supply 1, primary-side high-frequency inverter module 2, transmitting coil module 3, receiving coil module 4, secondary-side rectifier module 5, battery load 6, primary-side switched capacitor 7, secondary-side 1 switched capacitor 8, and secondary-side 2 switched capacitor 9.

[0098] In this configuration, DC power supply 1 is connected to the input terminal of primary-side high-frequency inverter module 2, the output terminal of high-frequency inverter 2 is connected to the input terminal of transmitting coil module 3, the output terminal of transmitting coil module 3 is positioned opposite to the input terminal of receiving coil module 4, the output terminal of receiving coil module 4 is connected to the input terminal of secondary-side rectifier module 5, the output terminal of secondary-side rectifier module 5 is connected to the system battery load 6, primary-side switching capacitor 7 is connected in series in the primary-side LCC topology, and secondary-side 1 switching capacitor 8 and secondary-side 2 switching capacitor 9 are connected in series in the secondary-side topology as compensation capacitors.

[0099] The primary-side DC input voltage V of the system dc The voltage is 628.3V. The transmitting coil current I1 has an amplitude of 28.15A. The secondary output currents I2 and I3 are 18.47A and 14.26A, respectively, and the secondary output voltages U2 and U3 are 277V and 285.1V, respectively. The system's driving frequency is 80kHz. The transmitting coil L1, receiving coil L2, and receiving coil L3 are wound with Litz wire to reduce the coil resistance. The inductance of each coil is 100μH, and the mutual inductance M between L1 and L2 and L3 is 30μH. The mutual inductance M between L2 and L3 is... 23 The compensation inductance is 10μH, L p The inductance value is 56.5μH, and the compensation capacitor C p The capacitance is 70nF. The initial values ​​of C2 and C3 are set to 39.6nF and 39.6nF respectively. Even when both secondary coils are in full resonance, C1 is set to 113nF. The values ​​of all filter capacitors are 2μF, which meets the filtering requirements.

[0100] Step 2, obtain the output voltage U of DC power supply 1. dc1 The signal is then output to the primary-side high-frequency inverter module, which outputs an 80kHz AC square wave to the primary-side coil. The specific steps include:

[0101] Step 2.1: Control the first switching transistor S among the primary-side switching capacitor 7, the secondary-side switching capacitor 8, and the secondary-side switching capacitor 9. x and the second switching transistor S y The system is kept in the on / off state with a certain duty cycle, so that β2 is 113°, β3 is 113°, and β1 is 120.7°, so that the system works in the full resonance state, which is also the initial state of the system. The voltage source is turned on and the system is judged to be working normally.

[0102] Step 2.2: Obtain the output voltage U of DC power supply 1 dc1 and output current I dc1 After passing through a high-frequency inverter, an AC square wave is obtained with an amplitude of U. dc1 The phase can be considered zero. According to Fourier decomposition, the decomposition formula of this voltage is:

[0103] (k is an odd number, ω is the angular frequency);

[0104] U can be obtained from the above formula. in =800sinωt, the current transmitted to the primary transmitting coil after the topology compensation structure is:

[0105]

[0106] Detection end for U in The value of I1 is sampled.

[0107] Step 3: Calculate the load impedance value using the voltage and current of the secondary load. The two secondary receiving coil modules obtain a suitable current through the primary transmitting coil. However, there is mutual inductance between the two secondary receiving coils, and current coupling occurs between the three coils. The specific process is as follows:

[0108] Ten voltage pulses were applied to the primary side. The measured secondary-side output currents I2 and I3 were 18.47A and 14.26A, respectively, and the secondary-side output voltages U2 and U3 were 277V and 285.1V, respectively. The equivalent resistances of the load were obtained, and the values ​​of R2 and R3 were 15Ω and 20Ω, respectively.

[0109] Step 4: Given the desired output power of the two sides, construct the load battery charging current control. Based on the theoretical analysis above, the specific set of equations can be constructed as follows:

[0110] Assume the desired output power P of both sides out2 4451W, P out3 If the current is 1853W, then the required current to be constructed is:

[0111]

[0112] It is easy to obtain that the amplitudes of I2 and I3 are 24.36A and 13.61A, respectively. The values ​​of C2 and C3 can then be derived using the formula:

[0113]

[0114] Under the premise of step 1, I2, I3 and C2, C3 satisfy Figure 18 and Figure 19 Surface diagram:

[0115] Therefore, C2 is 30 nF and C3 is 50 nF.

[0116] The first switching transistor S in the switching capacitor C2 on the secondary side 1 controls the switching transistor S. x2 and the second switching transistor S y2 Maintaining an on / off state with a certain duty cycle, it controls the first switching transistor S in the secondary-side switching capacitor C3. x3 and the second switching transistor S y3 Maintaining the on / off state with a certain duty cycle, the values ​​of C2 and C3 can be obtained through the following formula:

[0117]

[0118] In the above formula, based on the values ​​of C2 and C3, their respective conduction angles can be obtained: β2 = 90°, β3 = 133.4°.

[0119] Among them, C a For a fixed capacitor, C b These are series capacitors, each with a value of 50nF.

[0120] Step 5: Improve the overall system efficiency by controlling the primary-side switched capacitor C1:

[0121]

[0122] To optimize system transmission efficiency, based on step 1, a surface plot of C1 with respect to different values ​​of C2 and C3 is provided, such as... Figure 20 As shown.

[0123] Under this expected load power distribution, the system transmission efficiency is as follows:

[0124]

[0125] The system efficiency varies with I2 and I3 as follows: Figure 20 The relationship diagram shown:

[0126] Among them, the fixed capacitor C of the primary-side switching capacitor C1 a1 and series capacitor C b1 Both are 220nF, with a conduction angle β1 of 100.6°, P cu For system losses, Z in It is the input impedance, R in The input resistance is denoted by cosΦ, the power factor is η%, and the system efficiency is η%. The system efficiency is highest when the control power factor is at its maximum. in If the phase is zero, then by controlling C1, I... in With the imaginary part of zero, the system can achieve maximum efficiency.

[0127] To verify the correctness of the theory, a total of three simulations were conducted.

[0128] The first simulation was to verify the power distribution in the specific implementation plan. The control methods in the second and third simulations were the same as those in the first simulation, with the aim of achieving constant current control.

[0129] The first simulation used β2 = 90°, β3 = 133.4°, and the conduction angle β1 of the primary-side switched capacitor C1 = 108.5°. Taking into account all parasitic resistances in the circuit, the results are as follows: Figure 2 , Figure 3 , Figure 4 As shown.

[0130] The equivalent battery loads on the secondary side are 15Ω and 20Ω, respectively, with secondary side output currents of 17.3A and 9.2A, and the primary side output power is 6855W. Figure 4 As shown, the power received by secondary side 1 is 4592W, as... Figure 2 As shown, the power received by secondary side 2 is 1765W, as... Figure 4 As shown in the figure, the overall system transmission efficiency can be calculated to be 92.74%.

[0131] The second simulation set β2 to 114°, β3 to 114°, and the conduction angle of the primary-side switched capacitor C1 to 108.5°. Considering all parasitic resistances in the circuit, the results are as follows: Figure 5 , Figure 6 , Figure 7 As shown.

[0132] The equivalent battery loads on the secondary side are 20Ω and 25Ω, respectively, with secondary-side output DC currents of 12.08A and 10.51A, and the primary-side output power is 8855W. Figure 7 As shown, the power received by secondary side 1 is 4318W, as... Figure 5 As shown, the power received by secondary side 2 is 3634W, as... Figure 6 As shown in the figure. Therefore, the overall system transmission efficiency can be calculated to be 89.8%.

[0133] The third simulation set β2 to 114°, β3 to 133°, and the conduction angle of the primary-side switched capacitor C1 to 146°, and considered all parasitic resistances in the circuit. The results obtained are as follows. Figure 8 , Figure 9 , Figure 10 As shown.

[0134] The equivalent battery loads on the secondary side are 18Ω and 22Ω, respectively, with secondary-side output DC currents of 12.42A and 11.26A, and the primary-side output power is 7015W. Figure 10 As shown, the power received by secondary side 1 is 3140W, as... Figure 8 As shown, the power received by secondary side 2 is 3091W, as... Figure 9 As shown in the figure, the overall system transmission efficiency can be calculated to be 88.82%.

[0135] in Figure 11 , Figure 12 These are summary and classification diagrams of the above figures. Figure 13 , Figure 14 The diagrams show the control of the switching capacitors on the primary and secondary sides, respectively. The simulation results show a small error compared to the theoretical analysis, indicating that the theory is correct. (Note: Because the energy of the secondary battery should not be excessively released, the power rating is lower.)

[0136] This invention proposes a flexible charging technology based on switched capacitor control, taking into account the cross-coupling of the secondary coil. This technology can achieve target power distribution and enable safer and more reliable charging of the battery. When the battery state is different, the charging current can be regulated by the secondary-side compensation switched capacitor to achieve constant current charging of the battery. Furthermore, switched capacitor control is added to the LCC topology of the primary side of the system to further optimize the system transmission efficiency.

[0137] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0138] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment have been appropriately combined to form other embodiments that are easy for those skilled in the art to understand.

Claims

1. A switched capacitor compensation control method for a dual-load wireless power transfer system, characterized in that: Includes the following steps: Step 1: Construct the circuit topology diagram of the three-coil wireless power transmission system; Step 2: Obtain the output voltage U of the DC power supply dc1 It is then output to the primary-side high-frequency inverter module, which outputs an 80kHz AC square wave to the primary-side coil. Step 3: Calculate the load impedance value using the voltage and current of the secondary load; Step 4: Given the desired output power of the two secondary sides, construct the control equations for the charging current of the load battery; Step 5: Switch the capacitor on the primary side. Improve the overall efficiency of the system through control; Step 3 specifically includes: Step 3.1: Select a suitable power supply voltage U in Parallel compensation capacitor C of the resonant topology p A suitable output current I1 is obtained for the primary-side transmitting coil; Step 3.2: The two receiving coil modules on the secondary side obtain a suitable current through the transmitting coil on the primary side. However, there is also mutual inductance between the two receiving coils on the secondary side, and the currents of the three coils are coupled. By applying Kirchhoff's voltage theorem, the current flowing from the output to the two secondary transmitting coils is: ； ； Where L2 is the self-inductance of the transformer on the secondary side 1, and L3 is the self-inductance of the transformer on the secondary side 2; C2 represents the series compensation capacitor of the resonant topology of the secondary coil 2, i.e., the switched capacitor of the secondary side 1; R2 represents the parasitic resistance of the secondary coil 2; R eq2 C3 represents the series compensation capacitor of the resonant topology of secondary coil 3, i.e., the switching capacitor of secondary coil 2; R3 represents the parasitic resistance of secondary coil 3; R eq3 I2 represents the current flowing through the secondary coil 2, and I3 represents the current flowing through the secondary coil 3; M 12 M represents the mutual inductance between coils 1 and 2. 13 This represents the mutual inductance between coils 1 and 3. Because the two secondary coils are relatively close, the mutual inductance M between the two secondary coils is considered. 23 ; Step 4 specifically includes: Step 4.1: When the battery load impedance and mutual inductance of each side are not adjustable, the method of controlling the current by changing the series compensation capacitors C2 and C3 of the resonant topology of the secondary coil 2 has been given in step 3.2: ； ； The equations for C2 and C3 with respect to I2 and I3 are solved using an iterative method: ； ； Step 4.2: Control the first switching transistor S among the primary-side switching capacitor, secondary-side 1 switching capacitor, and secondary-side 2 switching capacitor. x and the second switching transistor S y The capacitance equation is as follows: Maintaining the on / off state with a certain duty cycle, the capacitance value is calculated as follows: ； Among them, C eq C represents the total capacitance of the switched capacitors. a For a fixed capacitor, C b For a series capacitor, β is the switching angle; Step 4.3: Control the magnitudes of the secondary coil currents i2 and i3 to change the power distribution between load battery 2 and load battery 3. The specific power calculation is as follows: ； ； In the above formula, P out2 P represents the amount of power received by battery load 2. out3 This indicates the amount of power received by battery load 3.

2. The switched capacitor compensation control method for a dual-load wireless power transmission system according to claim 1, characterized in that, Step 1 specifically includes: Step 1.1: Construct the circuit topology of the dual-load wireless power transmission system. The circuit topology specifically includes: a DC power supply, a primary-side high-frequency inverter module, a transmitting coil module, a receiving coil module, a secondary-side rectifier module, a battery load, a primary-side switched capacitor, a secondary-side 1 switched capacitor, and a secondary-side 2 switched capacitor. The DC power supply is connected to the input terminal of the primary-side high-frequency inverter module. The output terminal of the high-frequency inverter is connected to the input terminal of the transmitting coil module. The output terminal of the transmitting coil module is positioned opposite to the input terminal of the receiving coil module. The output terminal of the receiving coil module is connected to the input terminal of the secondary-side rectifier module. The output terminal of the secondary-side rectifier module is connected to the system battery load. The primary-side switched capacitor is connected in series in the primary-side LCC topology. The secondary-side 1 switched capacitor and the secondary-side 2 switched capacitor are connected in series in the secondary-side topology as compensation capacitors. Step 1.2: Control the primary side DC power supply to obtain a suitable output voltage, obtain a high-frequency voltage with zero phase through the high-frequency inverter, pass through the topology compensation coil structure to the transmitting coil module to the input voltage of the receiving coil module, the secondary side rectifier module converts the high-frequency AC power into DC power, and the secondary side battery load is connected to the output of the secondary side rectifier module to absorb power. Step 1.3: The primary-side switched capacitor, secondary-side 1 switched capacitor, and secondary-side 2 switched capacitor serve as compensation capacitors for the transmitting coil module and the receiving coil module. This is achieved by controlling the first switching transistor S among the primary-side switched capacitor, secondary-side 1 switched capacitor, and secondary-side 2 switched capacitor. x and the second switching transistor S y By maintaining the on / off state with a certain duty cycle, the equivalent capacitance of the primary-side switching capacitor, secondary-side 1 switching capacitor, and secondary-side 2 switching capacitor is changed to obtain a suitable capacitance value. The target output current is obtained by changing the capacitance values ​​of secondary-side 1 switching capacitor and secondary-side 2 switching capacitor. The reactive power of the one-to-two wireless power transmission system is changed by changing the capacitance value of the primary-side switching capacitor. Step 1.4: Determine the equivalent circuit of the one-to-two wireless power transmission system. Based on Kirchhoff's voltage and current laws, obtain a set of equations relating the input impedance and the relationship between the output power and the magnitude and phase of the voltage.

3. The switched capacitor compensation control method for a dual-load wireless power transmission system according to claim 1, characterized in that, Step 2 specifically includes: Step 2.1: Control the first switching transistor S among the primary-side switching capacitor, secondary-side 1 switching capacitor, and secondary-side 2 switching capacitor. x and the second switching transistor S y Maintain the on / off state with a certain duty cycle, turn on the voltage source and determine that the system is working normally; Step 2.2: Obtain the output voltage U of the DC power supply dc1 and output current I dc1 After passing through a high-frequency inverter, an AC square wave is obtained with an amplitude of U. dc1 The phase is considered to be zero, and the square wave voltage U is obtained according to Fourier decomposition. ac1 The decomposition formula is: ； Step 2.3: The acquired high-frequency voltage passes through the LCC resonant topology compensation circuit and reaches the transmitting coil. By Kirchhoff's voltage theorem, the following specific equation is obtained; ； Another L p C p Resonance, the resonant frequency is: ； Simplifying the above formula, the output current to the primary-side transmitting coil is: ； In the above formula, L p The compensating inductor of the resonant topology; C p Represents the parallel compensation capacitor of the resonant topology; U in U ac1 The fundamental component; I in Input current I ac1 fundamental component of .

4. The switched capacitor compensation control method for a dual-load wireless power transmission system according to claim 1, characterized in that, Step 5 specifically includes: Step 5.1: When the output power remains constant, the system efficiency η% and the input power P in Regarding the input impedance, assuming U in If the phase is zero, then the following equation holds: ； ； ； ； Where P in P represents the power input. cu For system losses, Z in It is the input impedance, R in The input resistance is η, cosΦ is the power factor, and η% is the system efficiency. Step 5.2: Control the power factor to be at its maximum; at this point, the system efficiency is highest. in If the phase is zero, then by controlling the first switching transistor S of the primary-side switching capacitor... x1 and the second switching transistor S y1 Maintaining the on / off state with a certain duty cycle, changing the value of C1, so that I in Since the imaginary part is zero, according to Kirchhoff's voltage theorem, the primary input current can be solved as follows: ； ； ； From the above formula, we obtain the vector expression: ； Among them, I' in With fixed size and phase, I C1 It is a purely imaginary number, and its size is adjustable. in There exists a minimum value, at which point I... in with I C1 Perpendicular to U in Vertical, so that the input reactive power is zero; From the vector expression, the topology loop vector diagram when C1 is not controlled is obtained. By controlling the value of C1 to maximize the power factor angle, the specific equation is as follows: ； The topology loop vector diagram at which the power factor angle is maximum is obtained: the relationship between each vector is derived from the vector diagram, and I is then analyzed through C1. in Phase adjustment achieves maximum system efficiency.

5. The switched capacitor compensation control method for a dual-load wireless power transmission system according to claim 1, characterized in that, During system operation, the state of the battery changes continuously with the degree of charging. In order to charge the battery with a certain appropriate power, constant current charging is adopted. The charging battery is controlled only by current to stabilize the output current. The current of the secondary side of the charging battery is collected by the signal acquisition and transmission module and compared with the rated charging current. Through PID control, excitation pulses are given to the three switched capacitors at the corresponding trigger angles to control the magnitude of the output current.

6. The switched capacitor compensation control method for a dual-load wireless power transmission system according to claim 1, characterized in that, Setting the power of a rechargeable battery requires measuring the equivalent load voltage drop across the battery, which is the product of the equivalent load voltage drop and the current. This is then compared with the ideal receiving power to obtain the desired input power. This is achieved by detecting the load voltage drop of the secondary rectifier bridge to obtain the output voltage, measuring the current in the receiving coil circuit to obtain the system's receiving power, and adjusting the excitation pulse of the switched capacitor to obtain the ideal input power.

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