Wireless power transmission double-closed-loop compound control system and method based on LCC-S compensation

Abstract

The invention discloses a wireless power transmission double-closed-loop compound control system and method based on LCC-S compensation, aims at the problem that the transmission efficiency of a wireless power transmission system is reduced due to load change, adopts a PI algorithm and a fuzzy PID algorithm to respectively control a primary side full-bridge inverter circuit and a secondary side DC-DC step-down chopper circuit, and has the advantages of simple circuit structure, low cost and the like. Reliability is high, efficiency is high, and maximum efficiency tracking of a wireless power transmission system is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of wireless power transmission, and relates to a wireless power transmission system based on LCC-S compensation and a double closed-loop composite control method thereof, and specifically to a wireless power transmission double closed-loop composite control system and method for maximum efficiency tracking. Background Art

[0002] With the deepening and development of scientific and technological research and the increase in people's demand for electricity, traditional power transmission technology can no longer meet people's requirements for power transmission in many aspects. Wireless power transmission technology came into being to solve this problem. Compared with traditional wired transmission methods, wireless power transmission systems have great advantages. Wireless power transmission technology effectively solves the instability caused by electrical contact and changes the limitations of electrical equipment flexibility being restricted by wires during charging. It has the convenience of no charging wires, so there is no need to plug and unplug wires when transmitting power.

[0003] Wireless power transmission technology can be divided into the following categories: electromagnetic radiation wireless power transmission technology, microwave wireless power transmission technology, laser wireless power transmission technology, magnetic field coupling wireless power transmission technology and electric field coupling wireless power transmission technology. Among them, magnetic field coupling wireless power transmission technology has the advantages of high transmission efficiency, long distance, high power and low sensitivity to coil misalignment.

[0004] At present, the main methods to improve the efficiency of magnetically coupled wireless power transmission systems are: 1. Optimizing the magnetic field coupling mechanism, that is, improving the coil structure and optimizing the parameters to improve the wireless power transmission efficiency; 2. The system efficiency under a fixed load is directly related to the input power, and the transmission efficiency is improved by controlling the input power point; 3. Using an active rectifier to control the change in the conduction angle of the switch tubes on the two bridges to track the maximum efficiency of the system; 4. Solving the frequency splitting problem through the resonant frequency tracking method, using a suitable control strategy to make the system operating frequency track the optimal operating frequency of the system to improve the system efficiency; 5. Achieving maximum efficiency tracking by changing the system equivalent load impedance.

[0005] With the widespread use of magnetic coupling resonant wireless transmission technology, in order to ensure high transmission efficiency, constant loads are often used as power supply objects in experiments. However, in the actual application of wireless power transmission, the load often changes, so the wireless power transmission system is often used in combination with energy storage devices. For example, electric vehicles are always powered by batteries, supercapacitors, or a combination of the two. The equivalent resistance of these power sources changes dynamically during the charging process, which will inevitably affect the charging current and system efficiency. Therefore, it is very necessary to optimize the transmission efficiency of the wireless power transmission system under variable load conditions.

[0006] Domestic and foreign scholars mainly use impedance matching technology and other means to achieve maximum efficiency tracking for traditional wireless power transmission systems, but they mainly focus on the matching network structure. Based on magnetic coupling wireless power transmission technology and combined with control technology, this invention proposes a wireless power transmission double closed-loop composite control system based on LCC-S compensation, which solves the problem of wireless power transmission efficiency reduction caused by load changes. Summary of the invention

[0007] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a wireless power transmission dual closed-loop composite control system and method based on LCC-S compensation. In order to solve the problem that the transmission efficiency of the wireless power transmission system decreases due to changes in the load, a PI algorithm and a fuzzy PID algorithm are used to control the primary side full-bridge inverter circuit and the secondary side DC-DC buck chopper circuit respectively. The circuit has a simple circuit structure, high reliability, high efficiency, and realizes maximum efficiency tracking of the wireless power transmission system.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A wireless power transmission composite control system based on LCC-S compensation includes an AC input circuit, a full-bridge rectifier circuit, a filter and voltage stabilizing capacitor C11, a full-bridge inverter circuit, a primary compensation network, a primary transmitting coil L2, a secondary receiving coil L3, a secondary compensation network, a full-bridge rectifier circuit, a DC-DC direct current chopper circuit, an output filter capacitor C0, a feedback control circuit composed of a controller, and a WiFi communication module. Diodes D11, D12, D13, and D14 form a primary side full-bridge rectifier circuit to rectify the AC power supply into direct current, Q1, Q2, Q3, and Q4 form a primary side full-bridge inverter circuit to invert direct current into high-frequency alternating current, L1, C1, and C2 form a primary side compensation network to improve the power factor of the circuit and improve the input and output characteristics; resistors R1 and R2 are the equivalent series resistances of L1 and L2 respectively, C3 is a secondary side compensation capacitor, and R3 is the equivalent series resistance of L3; the primary transmitting coil L2, the primary compensation network L1 , C1, C2, the secondary receiving coil L3 and the secondary compensation capacitor C3 form an LCC-S resonant compensation coupling network, C1 and C2 perform resonance compensation on L2, and C3 performs resonance compensation on L3; after comparing the output voltage U at both ends of the load with the reference output voltage Uref, the secondary side control logic is input and then the DC-DC duty cycle is controlled by the driver, and then the comparison result of the load voltage and the reference voltage is transmitted to the primary side through the WiFi module, and the input primary side is controlled by the primary side control logic and then the driver controls the primary side full-bridge inverter circuit to be alternately turned on.

[0010] The 220V AC input power is converted into a peak voltage of 310V after full-bridge rectification and C11 filtering. The full-bridge inverter circuit converts the voltage into a high-frequency square wave voltage, which is then converted into a high-frequency sinusoidal voltage through the primary-side LCC compensation network and applied to both ends of L2. L2 transfers the energy to L3, and the voltage at both ends of L3 is converted into a 30V voltage for the load after full-bridge rectification and DC-DC direct current chopper circuit. The primary and secondary side double closed-loop control circuits are used together to regulate the output voltage of the wireless power transmission system to achieve maximum efficiency tracking.

[0011] The beneficial effects of the present invention are:

[0012] The present invention mainly controls the secondary side DC-DC buck chopper circuit through fuzzy PID control and generates PWM modulation signal through PI closed-loop control and phase shift control to control the primary side full-bridge inverter circuit to achieve the maximum efficiency tracking of the wireless power transmission system, and proposes an effective and feasible method for the initial design and optimization of the maximum efficiency tracking composite control strategy of the wireless power transmission system.

[0013] The present invention only needs to construct PI closed-loop phase-shift control and fuzzy PID control in the primary and secondary side circuits of the wireless power transmission system to form a dual closed-loop composite control. The circuit structure is simple, the cost is low, the reliability is high during operation, and the maximum efficiency tracking of the wireless power transmission system can be achieved.

[0014] Since the primary side and the secondary side of the wireless power transmission system of the present invention are LCC-S type compensation networks, the device can output a constant voltage independent of the load at the same operating frequency to meet the requirements of constant voltage charging of the load. At the same time, the device works at one frequency point without frequency splitting and operates stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a circuit principle block diagram of the wireless power transmission system of the present invention;

[0016] Figure 2 It is the main circuit diagram of the wireless power transmission system of the present invention;

[0017] Figure 3 It is a functional relationship diagram of equivalent load resistance and charging time of the wireless power transmission system of the present invention;

[0018] Figure 4 is a functional relationship diagram of the wireless power transmission system efficiency and equivalent load resistance of the present invention;

[0019] Figure 5 It is a primary side control working state diagram of the wireless power transmission system of the present invention. DETAILED DESCRIPTION

[0020] The specific implementation manner and working principle of the present invention are further described in detail below with reference to the accompanying drawings.

[0021] like Figure 1 , 2 As shown, a wireless power transmission dual closed-loop composite control system based on LCC-S compensation includes a high-frequency AC power supply 1, a primary side bridge rectifier circuit 2, a primary side full-bridge inverter circuit 3, a primary side resonant compensation network 4, a primary side transmitting coil 5, a secondary side receiving coil 6, a secondary side resonant compensation network 7, a secondary side bridge rectifier circuit 8, a secondary side buck chopper circuit 9 and a load circuit 10, characterized in that:

[0022] The high-frequency AC power source 1 is connected to the primary side bridge rectifier circuit 2, the primary side full-bridge inverter circuit 3, the primary side resonant compensation network 4 and the primary side transmitting coil 5, and the secondary side receiving coil 6 is connected to the secondary side resonant compensation network 7, the secondary side bridge rectifier circuit 8, the secondary side buck chopper circuit 9 and the load circuit 10, and the primary side transmitting coil 5 is electromagnetically coupled with the secondary side receiving coil 6;

[0023] A primary WiFi communication module 11 is connected to the primary full-bridge inverter circuit 3, and the primary WiFi communication module 11 communicates with the secondary WiFi communication module 12 on the secondary side to transmit the load output voltage or output current. The output end of the primary WiFi communication module 11 is connected to the primary control logic circuit 13, and the control signal output by the primary control logic circuit 13 controls the operation of the above-mentioned primary bridge rectifier circuit 2 after passing through the primary drive circuit 14;

[0024] The secondary side buck chopper circuit 9 is connected to a comparator module 15, which is connected to a secondary side control logic circuit 16 after comparing the load output voltage U and the load reference voltage Uref. The control signal output by the secondary side control logic circuit 16 controls the secondary side buck chopper circuit 9 to work after passing through a secondary side drive circuit 17;

[0025] The primary resonant compensation network 4 and the secondary resonant compensation network 7 are composed of the primary capacitors C1, C2, the secondary capacitor C3, the primary inductor L1, and the primary and secondary coils L2, L3 to form the LCC-S resonant compensation network, which is used to improve the power factor and input-output characteristics of the wireless power transmission system.

[0026] The high-frequency AC power supply 1 is generated by a power supply U, the primary bridge rectifier circuit 2 is composed of a diode D11, a diode D12, a diode D13, and a diode D14, the primary full-bridge inverter circuit 3 is composed of a switch tube Q1, a switch tube Q2, a switch tube Q3, and a switch tube Q4, and the primary resonant compensation network 4 is composed of primary capacitors C1, C2, a primary inductor L1, and a primary coil L2 in series, wherein the primary capacitor C1 is connected in series between the primary capacitor C2 and the primary coil L2, and together with the primary capacitor C2 and the primary coil L2, constitutes a compensation network of a primary-side LCC structure, and the resistor R1 and the resistor R2 are the equivalent series resistances of the inductor L1 and the primary coil L2, respectively.

[0027] The secondary side resonant compensation network 7 is composed of a secondary side capacitor C3 and a secondary side coil L3 connected in series, wherein the resistor R3 is the series equivalent resistance of the secondary side coil L3, the secondary side bridge rectifier circuit 8 is composed of a diode D21, a diode D22, a diode D23, and a diode D24, the secondary side step-down chopper circuit 9 is composed of an IGBT switch tube SB, an inductor LB, and a diode DB, and the load circuit 10 is composed of a resistor RS, a resistor Rcp, and a capacitor C.

[0028] The full-bridge inverter circuit 3 is composed of a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4.

[0029] A dual closed-loop composite control system for wireless power transmission based on LCC-S compensation, characterized in that its control method comprises the following steps:

[0030] exist Figure 2 In the main circuit diagram of the wireless power transmission system, Kirchhoff's voltage law is applied in the primary and secondary LCC-S topology structures, and the following equations are obtained to describe this wireless power transmission system:

[0031]

[0032] In order to simplify the calculation and meet the resonance requirements, ω is approximated and it is considered that:

[0033]

[0034] Combining formula (1.1) and formula (1.2), the primary and secondary side resonant current phase currents I11, I12 and I21 can be obtained as follows:

[0035]

[0036] Through Fourier decomposition, the expressions of U1, I11, I12 and I21 are obtained as follows:

[0037]

[0038]

[0039] From this, we can derive the expressions of system output power and input power:

[0040]

[0041] From formula (1.6) and formula (1.7), the system conversion efficiency η can be obtained as:

[0042]

[0043] Substituting each item into the system efficiency expression, we can get the functional relationship between system efficiency and each parameter, such as Figure 3 shown.

[0044] When the supercapacitor charging current is constant, according to Kirchhoff's voltage law, the charging voltage across the supercapacitor can be obtained as:

[0045] U F (t) = I C R S +U C (1.9)

[0046] In the process of charging the supercapacitor, the change of the voltage US(t) across the supercapacitor from 0 to t is ΔUS. Then, in the stage of charging time from 0 to t, the supercapacitor charging current Ic can be expressed as:

[0047]

[0048] According to the above derivation, the equivalent load impedance RCL of the supercapacitor at time t can be expressed as:

[0049]

[0050] Substituting each term into the load impedance expression, we can obtain the functional relationship between load impedance and charging time, such as Figure 4 shown.

[0051] According to the functional relationship between load impedance and charging time and the functional relationship between system efficiency and various parameters, a composite control strategy is adopted to adjust the secondary side DC-DC buck chopper circuit and the primary side full-bridge inverter circuit to achieve maximum efficiency tracking of wireless power transmission efficiency.

[0052] On the primary side, the load impedance reference voltage value Uref is compared with the load impedance voltage output value U, and the comparison result is used as the PI closed-loop control input. After that, a PWM modulation signal is generated through phase shift control to control the alternating conduction of the full-bridge inverter circuit.

[0053] On the secondary side, the load impedance reference voltage value Uref is compared with the load impedance voltage output value U to obtain the error e and the error change rate ec as the input of the fuzzy controller. The fuzzy controller first fuzzifies the input, then performs fuzzy reasoning, and finally defuzzifies the result of the fuzzy reasoning to output the three parameters Kp, Ki, and Kd of the PID controller, thereby achieving the effect of adaptive tuning of the PID controller parameters. The outputs Kp, Ki, and Kd are obtained according to the fuzzy rule table to realize fuzzy PID control.

[0054] By adopting the PI phase shift control strategy in the wireless power transmission system, the primary full-bridge inverter circuit operates in five working modes, namely, mode 1-5. Figure 5 As shown, the switch can achieve zero voltage switching (ZVS) when turned on, and achieve approximately zero voltage turn-off (ZVT) under the action of parasitic capacitance.

[0055] The load-side comparator uses the error e between the load output voltage and the load reference voltage and its rate of change ec as the input of the fuzzy controller. These inputs are fuzzified in the fuzzy controller, and then the parameters kp, ki and kd of the PID controller are determined by fuzzy reasoning. This method combined with the primary-side PI phase-shift control structure can achieve maximum efficiency tracking of the wireless power transmission system.

[0056] like Figure 1 As shown, a wireless power transmission double-side composite control system based on LCC-S compensation includes a high-frequency AC power supply 1, a primary side bridge rectifier circuit 2, a primary side full-bridge inverter circuit 3, a primary side resonant compensation network 4, a primary side transmitting coil 5, a secondary side receiving coil 6, a secondary side resonant compensation network 7, a secondary side bridge rectifier circuit 8, a secondary side buck chopper circuit 9 and a load circuit 10. The primary side full-bridge inverter circuit 3 is connected to a primary side WiFi communication module 11, and the primary side WiFi communication module 11 communicates with the secondary side secondary side WiFi communication module 12 to transmit the load output voltage or output current. The primary side WiFi communication module 11 The output end is connected to the primary side control logic circuit 13, and the control signal output by the primary side control logic circuit 13 controls the operation of the primary side bridge rectifier circuit 2 after passing through the primary side drive circuit 14; the secondary side buck chopper circuit 9 is connected to the comparator module 15, which is connected to the secondary side control logic circuit 16 after comparing the load output voltage U and the load reference voltage Uref, and the control signal output by the secondary side control logic circuit 16 controls the operation of the secondary side buck chopper circuit 9 after passing through the secondary side drive circuit 17; the maximum efficiency tracking of the wireless power transmission system and the constant voltage output of the load are realized through the primary side and the secondary side double-side closed-loop composite control.

[0057] like Figure 2As shown, in the specific implementation process, the high-frequency AC power supply 1 is generated by the power supply U, the primary bridge rectifier circuit 2 is composed of a diode D11, a diode D12, a diode D13, and a diode D14, the primary full-bridge inverter circuit 3 is composed of a switch tube Q1, a switch tube Q2, a switch tube Q3, and a switch tube Q4, and the primary resonant compensation network 4 is composed of primary capacitors C1, C2, a primary inductor L1, and a primary coil L2 connected in series, wherein the primary capacitor C1 is connected in series between the primary capacitor C2 and the primary coil L2, and together with the primary capacitor C2 and the primary coil L2, constitutes a compensation network of the primary side LCC structure, and the resistor R1 and the resistor R2 are the equivalent series resistances of the inductor L1 and the primary coil L2, respectively.

[0058] The secondary side resonant compensation network 7 is composed of a secondary side capacitor C3 and a secondary side coil L3 connected in series, wherein the resistor R3 is the series equivalent resistance of the secondary side coil L3, the secondary side bridge rectifier circuit 8 is composed of a diode D21, a diode D22, a diode D23, and a diode D24, the secondary side step-down chopper circuit 9 is composed of an IGBT switch tube SB, an inductor LB, and a diode DB, and the load circuit 10 is composed of a resistor RS, a resistor Rcp, and a capacitor C.

[0059] When the input voltage on the primary side of the wireless power transmission system remains unchanged, the output voltage of the load terminal is mainly determined by the mutual inductance between the primary and secondary coils and the compensation inductance on the primary side. Therefore, in order to achieve dynamic stability of the output voltage and tracking of the maximum efficiency of the wireless power transmission system while keeping the input voltage and the primary-secondary structure unchanged, the present invention proposes a phase shift control strategy. By adopting a phase shift control strategy in the system, the switch can achieve zero voltage switching (ZVS) when turned on, and achieve approximate zero voltage shutdown (ZVT) under the action of parasitic capacitance. The model of the closed-loop wireless power transmission system on the primary side uses PI control to drive the phase shift angle of the waveform, thereby achieving a stable output voltage and tracking of the maximum transmission efficiency.

[0060] like Figure 5 As shown, since the full-bridge inverter circuit 3 is composed of a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4, by controlling the switch states of the switch tubes Q1, Q2, Q3 and Q4, the primary side network can have five working modes, which are Figure 5 Mode 1-5 is shown.

[0061] During mode 1, diode D01 and switch Q3 are turned on, and the current forms a loop through diode D01, switch Q3 and the primary-side LCC resonant compensation network. The primary current gradually decreases until the current reaches zero, thereby achieving zero voltage switching. The secondary-side current forms a loop through D21 and D24 in the full-bridge rectifier circuit.

[0062] During mode 2, the switch tube Q3 can achieve zero voltage shutdown under the buffering effect of capacitor C02. During the zero voltage shutdown process of the switch tube Q3, capacitor C3 is charged, capacitor C4 is discharged, and the current forms a loop through diode D01, capacitor C03, capacitor C04 and the primary side LCC compensation resonant network, and the secondary side current forms a loop through D21 and D24 in the full-bridge rectifier circuit.

[0063] During mode 3, the capacitor C4 finishes discharging, and the current forms a loop through the diode D04, the primary-side LCC compensation resonant network and the diode D01. After the current gradually decreases to zero, it begins to commutate and increase in the reverse direction, providing conditions for the zero-voltage turn-on of the switches Q1 and Q4. The secondary-side current forms a loop through D21 and D24 in the full-bridge rectifier circuit.

[0064] During mode 4, the switch tubes Q1 and Q4 are turned on at zero voltage, the current commutation ends, the current forms a loop through the switch tubes Q1, Q4 and the primary-side LCC compensation resonant network, and the secondary-side current forms a loop through D22 and D23 in the full-bridge rectifier circuit.

[0065] During mode 5, switch tube Q1 is turned off, switch tube Q4 continues to be turned on, and the current loop is transferred to capacitor C01 and capacitor C02. At this time, capacitor C01 is in a charging state and capacitor C02 is in a discharging state. Since the voltage across the capacitor cannot change suddenly, switch tube Q1 achieves zero voltage shutdown, and the secondary side current forms a loop through D22 and D23 in the full-bridge rectifier circuit.

[0066] On the secondary side, the error e between the target value and the output value and its rate of change ec are used as inputs to the fuzzy controller. First, these inputs are fuzzified in the fuzzy controller, and then the parameters kp, ki and kd of the PID controller are determined by fuzzy reasoning. This method can achieve adaptive adjustment of the PID controller parameters. According to the fuzzy rule table, the outputs kp, ki and kd are fuzzified to achieve fuzzy PID control. In this context, a two-dimensional fuzzy controller is designed to improve the control accuracy. The input variable of the fuzzy controller is the error e of the output voltage changing with time, where when e is a negative value, it means that the output voltage decreases, and when e is a positive value, it means that the output voltage increases. The magnitude of the error e reflects the amplitude of the output voltage change. The input variable ec = e / t represents the trend of the output voltage error e changing with time. When ec is a positive value, it means that the change of the error e is increasing, and when ec is a negative value, it means that the change of the error e is decreasing. The absolute value of ec is related to the slope of the change of the output voltage error. The specific input variable value determines the corresponding output variable value. After parameter optimization, fuzzy processing uses seven linguistic values ​​to establish membership functions for input and output variables: NB (negative large), NM (negative medium), NS (negative small), Z (zero), PS (positive small), PM (positive medium) and PB (positive large). The fuzzy control rules are shown in Table 1.

[0067] Table 1 Parameters K p Fuzzy control rule table

[0068]

[0069] Table 2 Parameters K i Fuzzy control rule table

[0070]

[0071] Table 3 Parameters K D Fuzzy control rule table

[0072]

Claims

1. A wireless power transmission dual closed-loop composite control system based on LCC-S compensation, comprising a high-frequency AC power supply 1, a primary side bridge rectifier circuit 2, a primary side full-bridge inverter circuit 3, a primary side resonant compensation network 4, a primary side transmitting coil 5, a secondary side receiving coil 6, a secondary side resonant compensation network 7, a secondary side bridge rectifier circuit 8, a secondary side buck chopper circuit 9 and a load circuit 10, characterized in that: The high-frequency AC power source 1 is connected to the primary side bridge rectifier circuit 2, the primary side full-bridge inverter circuit 3, the primary side resonant compensation network 4 and the primary side transmitting coil 5, and the secondary side receiving coil 6 is connected to the secondary side resonant compensation network 7, the secondary side bridge rectifier circuit 8, the secondary side buck chopper circuit 9 and the load circuit 10, and the primary side transmitting coil 5 is electromagnetically coupled with the secondary side receiving coil 6; A primary WiFi communication module 11 is connected to the primary full-bridge inverter circuit 3, and the primary WiFi communication module 11 communicates with the secondary WiFi communication module 12 on the secondary side to transmit the load output voltage or output current. The output end of the primary WiFi communication module 11 is connected to the primary control logic circuit 13, and the control signal output by the primary control logic circuit 13 controls the operation of the above-mentioned primary bridge rectifier circuit 2 after passing through the primary drive circuit 14; The secondary side buck chopper circuit 9 is connected to a comparator module 15, which is connected to a secondary side control logic circuit 16 after comparing the load output voltage U and the load reference voltage Uref. The control signal output by the secondary side control logic circuit 16 controls the secondary side buck chopper circuit 9 to work after passing through a secondary side drive circuit 17; The primary resonant compensation network 4 and the secondary resonant compensation network 7 are composed of the primary capacitors C1, C2, the secondary capacitor C3, the primary inductor L1, and the primary and secondary coils L2, L3 to form the LCC-S resonant compensation network, which is used to improve the power factor and input-output characteristics of the wireless power transmission system.

2. According to claim 1, a wireless power transmission double closed-loop composite control system based on LCC-S compensation is characterized in that: The high-frequency AC power supply 1 is generated by a power supply U, the primary bridge rectifier circuit 2 is composed of a diode D11, a diode D12, a diode D13, and a diode D14, the primary full-bridge inverter circuit 3 is composed of a switch tube Q1, a switch tube Q2, a switch tube Q3, and a switch tube Q4, and the primary resonant compensation network 4 is composed of primary capacitors C1, C2, a primary inductor L1, and a primary coil L2 in series, wherein the primary capacitor C1 is connected in series between the primary capacitor C2 and the primary coil L2, and together with the primary capacitor C2 and the primary coil L2, constitutes a compensation network of a primary-side LCC structure, and the resistor R1 and the resistor R2 are the equivalent series resistances of the inductor L1 and the primary coil L2, respectively.

3. According to claim 1, a wireless power transmission double closed-loop composite control system based on LCC-S compensation is characterized in that: The secondary side resonant compensation network 7 is composed of a secondary side capacitor C3 and a secondary side coil L3 connected in series, wherein the resistor R3 is the series equivalent resistance of the secondary side coil L3, the secondary side bridge rectifier circuit 8 is composed of a diode D21, a diode D22, a diode D23, and a diode D24, the secondary side step-down chopper circuit 9 is composed of an IGBT switch tube SB, an inductor LB, and a diode DB, and the load circuit 10 is composed of a resistor RS, a resistor Rcp, and a capacitor C.

4. According to claim 1, a wireless power transmission double closed-loop composite control system based on LCC-S compensation is characterized in that: The full-bridge inverter circuit 3 is composed of a switch tube Q1, a switch tube Q2, a switch tube Q3 and a switch tube Q4.

5. According to claim 1, a wireless power transmission double closed-loop composite control system based on LCC-S compensation is characterized in that: The control method includes the following steps: Step 1: In the main circuit of the wireless power transmission system, Kirchhoff's voltage law is applied in the primary and secondary LCC-S topology structures to obtain the following equations to describe the wireless power transmission system: In order to simplify the calculation and meet the resonance requirements, ω is approximated and it is considered that: Combining formula (1.1) and formula (1.2), the primary and secondary side resonant current phase currents I11, I12 and I21 can be obtained as follows: Through Fourier decomposition, the expressions of U1, I11, I12 and I21 are obtained as follows: From this, we can derive the expressions of system output power and input power: From formula (1.6) and formula (1.7), the system conversion efficiency η can be obtained as: Step 2: Substitute each item into the system efficiency expression, and the functional relationship between the system efficiency and each parameter can be obtained. When the supercapacitor charging current is constant, according to Kirchhoff's voltage law, the charging voltage across the supercapacitor can be obtained as: U F (t)=I C R S +U C (1.9) In the process of charging the supercapacitor, the change of the voltage US(t) across the supercapacitor from 0 to t is ΔUS. Then, in the stage of charging time from 0 to t, the supercapacitor charging current Ic can be expressed as: According to the above derivation, the equivalent load impedance RCL of the supercapacitor at time t can be expressed as: Step 3. Substitute each term into the load impedance expression to obtain the functional relationship between the load impedance and the charging time. According to the functional relationship between the load impedance and the charging time and the functional relationship between the system efficiency and various parameters, a composite control strategy is adopted to adjust the secondary side DC-DC buck chopper circuit and the primary side full-bridge inverter circuit to achieve maximum efficiency tracking of the wireless power transmission efficiency. Step 4: On the primary side, the load impedance reference voltage value Uref is compared with the load impedance voltage output value U, and the comparison result is used as the PI closed-loop control input, and then a PWM modulation signal is generated through phase shift control to control the full-bridge inverter circuit to alternately conduct; Step 5. On the secondary side, the load impedance reference voltage value Uref is compared with the load impedance voltage output value U to obtain the error e and the error change rate ec as the input of the fuzzy controller. The fuzzy controller first fuzzifies the input, then performs fuzzy reasoning, and finally defuzzifies the result of the fuzzy reasoning to output the three parameters Kp, Ki, and Kd of the PID controller, thereby achieving the effect of adaptive tuning of the PID controller parameters. The outputs Kp, Ki, and Kd are obtained according to the fuzzy rule table to realize fuzzy PID control.

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