A maximum efficiency tracking control method for battery wireless charging

Abstract

The application provides a maximum efficiency tracking control method for battery wireless charging, a layered cooperative control loop of "secondary side duty cycle adjustment" and "primary side input voltage disturbance" is constructed, and a time sequence conflict between battery charging management and system energy efficiency optimization is skillfully separated. A secondary side constant current / constant voltage PI controller monitors the battery terminal voltage / current in real time, adjusts the duty cycle of a Buck-Boost circuit quickly, strictly suppresses voltage / current fluctuations caused by load mutation or parameter drift, ensures that the battery is always in the best constant current or constant voltage charging state, effectively eliminates overcharging and undercharging risks, and guarantees the service life of the battery from the source. On this basis, through the top layer independently running efficiency tracking mechanism, the overall transmission efficiency of the system is actively optimized without affecting the accuracy of the battery constant current / constant voltage charging, and the technical problem that the battery protection and high efficiency transmission cannot be considered in the traditional wireless charging system is solved.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission and battery charging control technology, specifically relating to a control method that tracks the maximum efficiency operating point of a system by adjusting the output voltage of a primary-side controllable input power supply, and maintains constant current or constant voltage charging of the battery by adjusting the duty cycle of the Buck-Boost converter at the receiving end. Background Technology

[0002] With social development and progress, the pursuit of clean and sustainable energy and the improvement of the electrification level of the whole society have become inevitable trends. Since the Second Industrial Revolution, continuous innovation in electrical technology has profoundly promoted the leap in living standards and the development of all walks of life.

[0003] Traditional power transmission relies on physical connections such as metal wires, which has inherent limitations such as restricted wiring, poor flexibility, and susceptibility to contact sparks and wear. With the continuous improvement of social electrification, there is a growing demand for more flexible and convenient contactless power transmission solutions. Wireless power transfer technology is one such technology that transfers electrical energy from the power source to the load side without direct electrical contact. Among them, the magnetically coupled resonant wireless power transfer system has brought about a revolutionary change in the way electrical equipment is powered due to its unique advantages. This system enables instant charging, eliminating dependence on cables. It not only avoids safety risks such as leakage, short circuits, and electric sparks that may be caused by exposed wires or aging joints, but also significantly improves ease of use and safety. Furthermore, this technology supports simultaneous charging of multiple devices within the same power supply area, greatly enhancing the adaptability and flexibility of the power supply system.

[0004] Based on the above advantages, wireless power transmission technology can effectively break through the limitations of traditional wired power transmission methods, which is conducive to promoting the efficient use of energy, driving technological innovation and upgrading of related industries, improving the quality of life, supporting sustainable development goals, enhancing energy supply security, and expanding the application boundaries of scientific research, thereby having a profound impact on social and economic development and environmental protection.

[0005] In practical applications of wireless power transfer systems, when batteries are used as a load, a key issue is that the battery's equivalent load impedance undergoes significant dynamic changes with the charging process and state of charge. To effectively extend battery life while achieving fast charging, the system must continuously operate at its optimal efficiency and ensure a constant output voltage or current. This technical requirement not only ensures the stability of energy input during charging, preventing battery life reduction due to overcharging, overcurrent, and thermal runaway, but also significantly improves power transfer efficiency at the system level, achieving a highly efficient and safe charging process. Achieving this goal is of indispensable importance for optimizing the overall performance of the entire wireless power transfer system.

[0006] In view of this, the present invention provides a solution that can extend battery life while ensuring charging efficiency. Summary of the Invention

[0007] This invention provides a maximum efficiency tracking control method for wireless battery charging, which aims to ensure charging efficiency while extending battery life and improving system reliability in the face of dynamic changes in battery charging state.

[0008] To achieve the above objectives, the technical solution provided by this invention is:

[0009] A magnetically coupled resonant wireless power transfer system for wireless battery charging is characterized by comprising a controllable input power supply, an inverter, a compensation circuit, a rectifier circuit, a DC / DC converter module, a battery, a wireless communication module, a primary-side maximum efficiency tracking controller, and a secondary-side constant current / constant voltage PI controller.

[0010] The output terminal of the controllable input power supply is connected to the input terminal of the inverter, which serves as the power input for the entire wireless power transmission system to provide an adjustable DC voltage for the "disturbance input voltage" operation in maximum efficiency tracking control; the inverter is used to convert DC power into high-frequency AC power to supply the compensation circuit.

[0011] The compensation circuit includes a transmitter compensation network and a receiver compensation network; the input of the transmitter compensation network is connected to the output of the inverter, and the output of the receiver compensation network is connected to the input of the rectifier circuit; the transmitter coil of the transmitter compensation network and the receiver coil of the receiver compensation network together constitute a magnetic coupling mechanism, which wirelessly transmits electrical energy from the transmitter to the receiver through magnetic coupling resonance.

[0012] The rectifier circuit rectifies the high-frequency AC power received by the compensation network at the receiving end into DC power, which is then supplied to the subsequent DC / DC converter module.

[0013] The DC / DC conversion module adopts a Buck-Boost circuit, the input end of which is connected to the output end of the rectifier circuit, and the output end is connected to the battery;

[0014] The secondary side constant current / constant voltage PI controller collects the battery voltage U bat and the battery current I bat , and adjusts the Buck-Boost converter duty cycle D according to the error between I bat and the constant current reference value I ref in the constant current charging stage, and adjusts the duty cycle D according to the error between U bat and the constant voltage reference value U ref in the constant voltage charging stage, so that the battery terminal current or voltage is kept within the preset range.

[0015] The wireless communication module sends the battery voltage U bat , the battery current I bat , the charging phase flag and the battery terminal stable state collected by the secondary side constant current / constant voltage PI controller to the primary side maximum efficiency tracking controller (also a PI controller), and the primary side maximum efficiency tracking controller evaluates the system efficiency and issues adjustment instructions; the primary side maximum efficiency tracking controller also collects the input voltage U in and the input current I in of the controllable input power supply output end, and calculates the system efficiency η according to the input power P in and the battery output power P out , and the system efficiency of the kth working point is:

[0016] .

[0017] That is, the present application is controlled by the secondary side constant current / constant voltage PI controller and the primary side maximum efficiency tracking controller; wherein the secondary side constant current / constant voltage PI controller constructs a secondary side constant current / constant voltage control loop, which is a fast inner loop; the primary side maximum efficiency tracking controller constructs a primary side maximum efficiency tracking control loop, which is a slow outer loop. The outer loop pauses updating the disturbance direction after adjusting the input voltage each time, and the inner loop adjusts the duty cycle D in priority; when the battery terminal meets the preset stable condition, the outer loop calculates the stable efficiency after disturbance and decides the next input voltage adjustment direction. The outer loop adjustment period is greater than the stable time of the inner loop, and is not limited to a fixed time ratio.

[0018] The above stable conditions include at least one of the following: in the constant current stage, the battery current satisfies , and ε I is the current deviation threshold; in the constant voltage stage, the battery voltage satisfies , U is a voltage deviation threshold; the above conditions are continuously met for a preset sampling number Ns; or the change rate of the battery current and the battery voltage is lower than a preset threshold.

[0019] Further, the compensation circuit adopts an LCC-LCC resonant compensation circuit.

[0020] The transmitting end compensation network comprises a compensation inductor L f1 , a compensation capacitor C1, and a compensation capacitor C f1 , and a transmitting coil L p ; the compensation inductor L f1 and the compensation capacitor C1 are connected in series on a main path; a parallel branch connected with the compensation capacitor C f1 is led out at a node between the compensation inductor L f1 and the compensation capacitor C1, and connected to one end of the inverter; one end of the transmitting coil L p is connected to the other end of the compensation capacitor C1, and the other end of the transmitting coil L p is connected to the other end of the inverter;

[0021] The receiving end compensation network comprises a receiving coil L s , a compensation capacitor C2, a compensation inductor L f2 , and a compensation capacitor C f2 ; one end of the receiving coil Ls is connected to one end of a rectifier, and the other end is connected in series with the compensation capacitor C2; the main path is connected in series with the compensation inductor L f2 after the compensation capacitor C2; a parallel branch connected with the compensation capacitor C f2 is led out at a node between the compensation capacitor C2 and the compensation inductor L f2 , and connected to the other end of the rectifier;

[0022] The LCC-LCC resonant compensation circuit can filter out high-order harmonics, so that the transmitting coil current is determined only by the compensation inductor L f1 , and a constant reactive current flows in the transmitting coil, and the inverter output current is zero when the receiving end is far away from the transmitting end.

[0023] Further, the LCC-LCC resonant compensation circuit satisfies the following conditions when the system resonates:

[0024]

[0025] wherein j is an imaginary unit; and ω is the working angular frequency of the system.

[0026] At this time, the inductive reactance and capacitive reactance parameters of the transmitting end compensation network and the receiving end compensation network satisfy the preset resonant matching condition, so that the system works at the set resonant frequency, and the reactive power is offset.

[0027] Further, the output voltage V o is less than the input voltage V in satisfies the relationship:

[0028]

[0029] When 0 < D < 0.5, it is a step-down operation mode; when 0.5 < D < 1, it is a step-up operation mode.

[0030] Meanwhile, the application also provides a maximum efficiency tracking control method based on the above-mentioned magnetic coupling resonance type wireless power transmission system, and the speciality thereof lies in comprising the following steps:

[0031] Step 1, inner loop stability control

[0032] The secondary side constant current / constant voltage control inner loop is started, the duty cycle of the DC / DC converter is adjusted in real time, so that the charging state of the battery end is kept stable; when the battery end current or voltage deviation continuously meets the preset condition, it is determined that the battery end reaches the stable state;

[0033] Step 2, outer loop disturbance optimization

[0034] 2.1) After the battery end is stabilized, the system parameters are collected and the system efficiency of the current stable working point is calculated;

[0035] 2.2) The primary side maximum efficiency tracking control outer loop adjusts the output voltage of the controllable input power supply according to the preset first voltage disturbance step and disturbance direction; after the voltage is adjusted, the outer loop disturbance is suspended, and the inner loop is waited to adjust the battery end to stable again;

[0036] 2.3) After the battery end is stabilized again, the efficiency change is calculated:

[0037] When the efficiency change is in the threshold range, it is determined that the system enters the maximum efficiency point neighborhood, and the optimal input voltage is recorded;

[0038] If the efficiency is improved, the current disturbance direction is kept until the system enters the maximum efficiency point neighborhood;

[0039] If the efficiency decreases, the disturbance direction is reversed, and the disturbance step is switched from the first voltage disturbance step to the second voltage disturbance step until the system enters the maximum efficiency point neighborhood; wherein the second voltage disturbance step is smaller than the first voltage disturbance step;

[0040] Step 3, periodic monitoring and re-optimization

[0041] The system keeps the optimal input voltage to continue charging, and periodically monitors the system efficiency:

[0042] ① When a change in coil coupling state or a decrease in system efficiency is detected, a re-optimization is triggered;

[0043] When the switch from constant current charging stage to constant voltage charging stage is detected, the maximum efficiency tracking outer loop is paused to avoid misjudging the power change caused by the charging stage switch as the efficiency change caused by the input voltage disturbance; after the new charging stage stabilizes, the reference efficiency is recalculated and the outer loop optimization logic is restored.

[0044] After triggering the re-optimization, the second voltage perturbation step size is adopted, and the current input voltage is used as the initial value. Then, the process returns to step 2 until charging is completed.

[0045] ② If no re-optimization is triggered, the system maintains the optimal input voltage and continues to monitor efficiency according to the preset cycle until charging is completed.

[0046] Furthermore, during the execution of the maximum efficiency tracking control method, both the input voltage and duty cycle are limited by preset safety limits. When any variable reaches its limit, or when battery overvoltage, overcurrent, communication interruption, or sampling abnormality occurs, the system suspends maximum efficiency tracking, maintains or reduces the input power, and the secondary side constant current / constant voltage control inner loop or system safety protection mechanism prioritizes the execution of safety control.

[0047] The advantages of this invention are:

[0048] 1. This invention cleverly eliminates the timing conflict between battery charging management and system energy efficiency optimization by constructing a hierarchical collaborative control loop of "secondary-side duty cycle adjustment" and "primary-side input voltage disturbance". The secondary-side constant current / constant voltage PI controller monitors the battery terminal voltage / current in real time. By rapidly adjusting the duty cycle of the Buck-Boost circuit, it strictly suppresses voltage / current fluctuations caused by load changes or parameter drift, ensuring that the battery is always in the optimal constant current or constant voltage charging state. This effectively eliminates the risks of overcharging and undercharging, guaranteeing the battery's lifespan from the source. Furthermore, through a top-level independently operating efficiency tracking mechanism, the overall system transmission efficiency is actively optimized without affecting the battery's constant current / constant voltage charging accuracy, solving the technical challenge of balancing "battery protection" and "high-efficiency transmission" in traditional wireless charging systems.

[0049] 2. The maximum efficiency tracking mechanism employed in this invention breaks away from the reliance of traditional magnetically coupled resonant systems on complex impedance matching or cumbersome mathematical analytical models. This method involves real-time perturbation of the voltage of the controllable input power supply on the primary side in set steps, and using a wireless communication module to calculate the global system efficiency. By comparing the efficiency difference before and after the perturbation, the system autonomously determines the direction of efficiency ramp-up, automatically approaches and continuously locks onto the system's maximum efficiency operating point under the current operating conditions. This allows the system to achieve adaptive and efficient operation over a wide power range and with varying coupling coefficients without requiring manual preset of the optimal operating frequency or load impedance.

[0050] 3. In practical applications, the equivalent load of wireless power transfer systems often drifts unpredictably due to ambient temperature, coil relative position (offset), and battery SOC. The primary-side maximum efficiency tracking control outer loop of this invention addresses this challenge. It does not rely on a fixed theoretical model but instead performs closed-loop optimization based on real-time input-output efficiency feedback. Whenever system characteristics change (e.g., the efficiency peak point shifts), this mechanism can continuously detect efficiency changes and actively adjust the input voltage, quickly pulling the system back to a new optimal operating state. This adaptive optimization characteristic endows the system with excellent robustness and self-regulation capabilities, enabling long-term, high-efficiency operation under unattended conditions.

[0051] 4. This invention, through its secondary-side constant current / constant voltage control inner loop, endows the system with strong immunity to changes in the battery's own state. As the lithium battery undergoes charge-discharge cycles, its equivalent internal resistance naturally increases. The secondary-side constant current / constant voltage control inner loop of this invention does not rely on a precise model of the battery's internal resistance, but directly acquires the real-time voltage / current values ​​at the battery port. When a change in the battery's equivalent impedance causes a deviation from the target value, the secondary-side constant current / constant voltage PI controller can automatically calculate the deviation and increase or decrease the duty cycle of the Buck-Boost main switch to compensate for the impact of impedance changes, strictly maintaining a constant output voltage or current. This ensures that even under conditions of battery aging or drastic changes in state of charge, the system can still maintain a constant current or constant voltage output. Attached Figure Description

[0052] Figure 1 This is a circuit diagram of the wireless charging system for batteries according to the present invention;

[0053] Figure 2 This is a flowchart of the disturbance adjustment process of the present invention. Detailed Implementation

[0054] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0055] This embodiment provides a maximum efficiency tracking control method for a magnetically coupled resonant wireless power transfer system. For example... Figure 1 As shown, the magnetically coupled resonant wireless power transfer system includes a controllable input power supply, an inverter, a compensation circuit, a rectifier circuit, a DC / DC converter module, a battery, a wireless communication module, a primary-side maximum efficiency tracking controller, and a secondary-side constant current / constant voltage PI controller.

[0056] The output of the controllable input power supply is connected to the input of the inverter to provide an adjustable DC voltage.

[0057] The compensation circuit adopts an LCC-LCC resonant compensation circuit, including a transmitter compensation network and a receiver compensation network. The input of the transmitter compensation network is connected to the output of the inverter, and the output of the receiver compensation network is connected to the input of the rectifier circuit. The transmitting coil of the transmitter compensation network and the receiving coil of the receiver compensation network together form a magnetic coupling mechanism, which wirelessly transmits electrical energy from the transmitter to the receiver through magnetic coupling resonance. The specific topology connection is as follows: The transmitter compensation network includes a compensation inductor L... f1 Compensation capacitor C1, compensation capacitor C f1 and transmitting coil L p Compensating inductor L f1 The compensation capacitor C1 and the compensation inductor L are connected in series in the main circuit; f1 A parallel branch is drawn from the node between the compensation capacitor C1 and the compensation capacitor C2 to connect the compensation capacitor C3. f1 One end of the inverter is connected to the inverter; the end of the compensation capacitor C1 is connected to the transmitting coil L. p One end, transmitting coil L p The other end connects to the other end of the inverter. The receiver compensation network includes the receiving coil L. s Compensating capacitor C2, compensating inductor L f2 and compensation capacitor C f2 One end of the receiving coil Ls is connected to one end of the rectifier, and the other end is connected in series with a compensation capacitor C2; after the compensation capacitor C2, the main circuit is connected in series with a compensation inductor L. f2 ; In the compensation capacitor C2 and compensation inductor L f2 At the node between them, a parallel branch is led out to connect the compensation capacitor C. f2 To the other end of the rectifier.

[0058] The working principle of this LCC-LCC resonant compensation circuit is as follows: When the system is designed by parameters to operate at the resonant frequency:

[0059]

[0060] The current in the transmitting coil is supplied by the compensating inductor L on this side. f1 This design achieves constant current output at the transmitting end, independent of the load state at the receiving end. Therefore, when the receiving end is unloaded, only a constant reactive current flows through the transmitting coil, while the inverter output current approaches zero, automatically avoiding the risk of a system short circuit. Simultaneously, this structure effectively filters harmonics, improving power quality. Parameter settings are achieved through compensation inductor L... f1 Inductance value, compensation capacitor C f1 The capacitance value of the compensation capacitor C1 is calculated based on the capacitance value and the inductance value of the transmitting coil; the capacitance value is then calculated using the compensation inductance L. f2 Inductance value, compensation capacitor C f2the capacitance of the compensation capacitor C2 is calculated based on the capacitance value and the inductance value of the receiving coil, so that the capacitive property and resistive property of the system cancel each other out, reducing reactive power and improving transmission efficiency. The LCC-LCC resonant compensation circuit can also filter out high-order harmonics generated in the energy conversion link, reduce the influence of harmonics on the magnetically coupled resonant wireless power transmission system, improve power quality, reduce interference to other electronic devices, and help improve the overall performance and stability of the system.

[0061] The DC / DC conversion module adopts a Buck-Boost buck-boost circuit, whose input end is connected to the output end of the rectifier circuit, and the output end is connected to the battery. The Buck-Boost circuit comprises a main switching tube Q5, an energy storage inductor L1, a diode D5 and a capacitor C4. Its working principle is as follows: when the main switching tube Q5 is turned on, the rectified and filtered voltage charges the energy storage inductor L1 through Q5, and the inductor current increases linearly. At this time, the diode D5 is cut off, and the capacitor C4 supplies power to the load (battery R L ); when the main switching tube Q5 is turned off, the energy storage inductor L1 generates a reverse induced electromotive force, the diode D5 is conducted, and L1 forms a freewheeling loop through D5 and C4, charging the capacitor C4 and supplying power to the load. If the inductor current drops to zero, only C4 discharges to the load (battery R L ), controlling the main switching tube Q5 to be turned on and off repeatedly, a negative output voltage can be obtained at the load (battery R L ), and the DC / DC conversion circuit can realize voltage boosting and bucking of the output voltage.

[0062] Let T be the period, T on is the conduction time, T off is the turn-off time, and D is the duty cycle . According to the volt-second balance principle of inductors, after the circuit enters a stable working state, the integral of the voltage across the inductor over time in one period should approach zero, we have: ; , thus the output voltage V o can be expressed as:

[0063]

[0064] When 0<D<0.5, the circuit is equivalent to a buck circuit; when 0.5<D<1, the circuit is equivalent to a boost circuit. The relationship between the duty cycle D and the input voltage and output voltage can be derived as:

[0065]

[0066] By changing the duty cycle D of the Buck-Boost converter, the load voltage / current remains constant even when the battery's equivalent impedance changes. When the secondary-side constant current / constant voltage PI controller receives a negative input load current / voltage, compared to the load's rated current / voltage, if the load current / voltage is less than the rated current / voltage, the equivalent duty cycle D output by the secondary-side constant current / constant voltage PI controller increases, extending the conduction time of switch VD and consequently increasing the current / voltage across the load resistor. Conversely, if the load current / voltage is greater than the rated current / voltage, the equivalent duty cycle D output by the secondary-side constant current / constant voltage PI controller decreases, shortening the conduction time of the main switch Q5 and consequently decreasing the current / voltage across the load resistor. When the difference between the load current / voltage and the rated current / voltage is zero, the load current / voltage stability is ensured. Appropriate parameters improve current / voltage stability, thus extending battery life during charging.

[0067] Based on the above system, this embodiment adopts the following maximum efficiency tracking control method, the specific process of which is as follows: Figure 2 As shown:

[0068] Step 1: Establish the topology model of the magnetically coupled resonant wireless power transmission system, and design parameters to make the system work at the resonant frequency, so as to achieve constant current output at the transmitting end and cancel reactive power.

[0069] Step 2: Initialize the input voltage disturbance direction d and the first voltage disturbance step size ΔU L Second voltage disturbance step size ΔU S Efficiency judgment threshold Re-optimizing the threshold The upper and lower limits of the controllable input voltage and the upper and lower limits of the Buck-Boost duty cycle, where d takes the value of +1 or -1, and Greater than At the start of maximum efficiency tracking, the first input voltage perturbation step size ΔU is used. L ;

[0070] Step 3: Activate the secondary-side constant current / constant voltage control inner loop according to the current charging stage of the battery; during the constant current charging stage, the secondary-side constant current / constant voltage PI controller adjusts the control based on the battery current I... bat With constant current reference value I ref To adjust the duty cycle D of the Buck-Boost converter to maintain the battery charging current within a preset range, the deviation between the two is considered. During the constant voltage charging phase, the secondary-side constant current / constant voltage PI controller adjusts the current based on the battery voltage U. bat With constant pressure reference value U ref To compensate for the deviation between the two, adjust the duty cycle D of the Buck-Boost converter to keep the battery charging voltage within the preset range;

[0071] When the constant current charging stage satisfies: Or, during the constant voltage charging phase, the following conditions must be met: Furthermore, when the corresponding conditions are met continuously for a preset number of Ns sampling cycles, it is determined that the battery has reached a stable state, and the primary side is allowed to track the outer loop of the maximum efficiency control.

[0072] Step 4: Provided that the battery voltage / current is stable as in Step 3, execute the maximum efficiency tracking mechanism.

[0073] 4.1) Acquire the input voltage U at the output terminal of the controllable input power supply. in Input current I in and battery voltage U bat Battery current I bat Calculate the system efficiency at the current stable operating point. ;

[0074] 4.2) The primary-side maximum efficiency tracking control outer loop adjusts the output voltage of the controllable input power supply according to the preset first voltage disturbance step size and disturbance direction:

[0075]

[0076] After the input voltage is adjusted, the primary side maximum efficiency tracking control outer loop keeps the current command unchanged, while the secondary side constant current / constant voltage control inner loop continues to run and readjusts the duty cycle D until the battery terminal meets the stability condition again.

[0077] 4.3) After the battery terminal regains stability, calculate the system efficiency at the current stable operating point. and efficiency change :

[0078]

[0079] When the efficiency change is consecutively preset number of times Satisfy: |Δη(k)|≤ε η If the current operating point is within the neighborhood of the maximum efficiency point, then the current input voltage is maintained or the perturbation step size is reduced, and the current optimal efficiency is recorded. and corresponding input voltage ;

[0080] when When this occurs, it indicates that the current perturbation direction can significantly improve the system efficiency. Keep the perturbation direction d unchanged until the system enters the neighborhood of the point with maximum efficiency.

[0081] when When the current perturbation direction significantly reduces system efficiency, it indicates that the current operating point has approached or exceeded the maximum efficiency operating point. Therefore, d = -d is set to reverse the perturbation direction until the system enters the neighborhood of the maximum efficiency point. If the current voltage perturbation step size ΔU is used... L Then the input voltage perturbation step size is switched to the second input voltage perturbation step size ΔU. S And continue to perform small-step optimization along the reversed perturbation direction; if the second input voltage perturbation step size ΔU has already been adopted. S If the second input voltage perturbation step size remains unchanged, the perturbation direction is reversed to continue the optimization process;

[0082] 4.4) Entering periodic monitoring state within the neighborhood of the maximum efficiency point. In this periodic monitoring state, the system maintains the optimal input voltage. Continue charging and collect input and output parameters and calculate monitoring efficiency according to a preset cycle. If the deviation of the monitoring efficiency from the recorded optimal efficiency exceeds the re-optimization threshold... If a switch between constant current / constant voltage charging stages, a change in coil coupling state, or a significant change in input / output power is detected, a re-optimization is triggered. When re-optimization is triggered, the current input voltage is used as the initial input voltage for re-optimization. The re-optimization uses a second voltage perturbation step size ΔU. S (Return to step 4.1) to perform local optimization near the original maximum efficiency operating point or the stable operating point in the new charging phase. If no re-optimization is triggered, the system maintains the optimal input voltage. It will continue to monitor efficiency according to the preset cycle until charging is complete.

[0083] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A magnetically coupled resonant wireless power transfer system for wireless battery charging, characterized in that, It comprises a controllable input power supply, an inverter, a compensation circuit, a rectifier circuit, a DC / DC conversion module, a battery, a wireless communication module, a primary-side maximum efficiency tracking controller and a secondary-side constant current / constant voltage PI controller; The output end of the controllable input power supply is connected to the input end of the inverter, and is used for providing an adjustable DC voltage; The compensation circuit comprises a transmitting-side compensation network and a receiving-side compensation network; the input end of the transmitting-side compensation network is connected to the output end of the inverter, and the output end of the receiving-side compensation network is connected to the input end of the rectifier circuit; the transmitting coil of the transmitting-side compensation network and the receiving coil of the receiving-side compensation network jointly form a magnetic coupling mechanism, and electric energy is wirelessly transmitted from the transmitting side to the receiving side by means of magnetic coupling resonance; The DC / DC conversion module adopts a Buck-Boost circuit, the input end of which is connected to the output end of the rectifier circuit, and the output end of which is connected to the battery; The secondary-side constant current / constant voltage PI controller collects the battery voltage U. bat and battery current I bat During the constant current charging phase, according to I bat With constant current reference value I ref The error between the two is adjusted by regulating the duty cycle D of the Buck-Boost converter, which is based on U during the constant voltage charging phase. bat With constant pressure reference value U ref The duty cycle D of the error adjustment between the two is used to keep the battery terminal current or voltage within a preset range; The wireless communication module will collect the battery voltage U from the secondary-side constant current / constant voltage PI controller. bat Battery current I bat The charging stage indicator and battery stability status are sent to the primary-side maximum efficiency tracking controller, which then evaluates the system efficiency and issues adjustment commands. Simultaneously, the primary-side maximum efficiency tracking controller acquires the input voltage U at the output of the controllable input power supply. in and input current I in The system efficiency is calculated based on the input power and the battery output power.

2. The magnetically coupled resonant wireless power transfer system according to claim 1, characterized in that: The compensation circuit adopts an LCC-LCC resonant compensation circuit; The transmitter compensation network includes a compensation inductor L. f1 Compensation capacitor C1, compensation capacitor C f1 and transmitting coil L p Compensating inductor L f1 The compensation capacitor C1 and the compensation inductor L are connected in series in the main circuit; f1 A parallel branch is drawn from the node between the compensation capacitor C1 and the compensation capacitor C2 to connect the compensation capacitor C3. f1 One end of the inverter is connected to the inverter; the end of the compensation capacitor C1 is connected to the transmitting coil L. p One end, transmitting coil L p The other end connects to the other end of the inverter; The receiver compensation network includes a receiver coil L s Compensating capacitor C2, compensating inductor L f2 and compensation capacitor C f2 One end of the receiving coil Ls is connected to one end of the rectifier, and the other end is connected in series with a compensation capacitor C2; after the compensation capacitor C2, the main circuit is connected in series with a compensation inductor L. f2 ; In the compensation capacitor C2 and compensation inductor L f2 At the node between them, a parallel branch is led out to connect the compensation capacitor C. f2 To the other end of the rectifier.

3. The magnetically coupled resonant wireless power transfer system according to claim 2, characterized in that: The LCC-LCC resonant compensation circuit satisfies the following when the system resonates: wherein j is the imaginary unit; ω is the working angular frequency of the system.

4. The magnetically coupled resonant wireless power transfer system according to claim 1 or 2, characterized in that: The output voltage V of the Buck-Boost circuit o With input voltage V in Satisfying Relationship: when 0<D<0.5, the system operates in a step-down working mode, and when 0.5<D<1, the system operates in a step-up working mode.

5. A maximum efficiency tracking control method based on the magnetically coupled resonant wireless power transfer system according to any one of claims 1-4, characterized in that, comprising the following steps: Step 1, Inner-loop stability control Start the constant current / constant voltage control inner loop on the secondary side, and keep the charging state of the battery end stable by adjusting the duty cycle of the DC / DC converter in real time; when the current or voltage deviation of the battery end continuously meets the preset condition, it is determined that the battery end reaches a stable state; Step 2, Outer-loop disturbance optimization 2. 1) After the battery end is stabilized, collect system parameters and calculate the system efficiency at the current stable working point; 2.2) The primary-side maximum efficiency tracking control outer loop adjusts the output voltage of the controllable input power supply according to a preset first voltage disturbance step size and a preset disturbance direction; after the voltage adjustment, the outer-loop disturbance is suspended, and the inner loop is waited to adjust the battery end to be stable again; 2.3) After the battery end is stabilized again, calculate the efficiency change amount: when the efficiency change is within the threshold range, determine that the system enters the neighborhood of the maximum efficiency point, and record the optimal input voltage; if the efficiency increases, maintain the current disturbance direction until the system enters the neighborhood of the maximum efficiency point; if the efficiency decreases, reverse the disturbance direction, and switch the disturbance step size from the first voltage disturbance step size to a second voltage disturbance step size until the system enters the neighborhood of the maximum efficiency point; wherein the second voltage disturbance step size is smaller than the first voltage disturbance step size; Step 3, Cyclic monitoring and re-optimization the system maintains the optimal input voltage to continue charging, and monitors the system efficiency periodically: ① when the change of coil coupling state or the decrease of system efficiency is monitored, trigger re-optimization; When the switch from constant current charging stage to constant voltage charging stage is detected, the maximum efficiency tracking outer loop is paused to avoid misjudging the power change caused by the charging stage switch as the efficiency change caused by the input voltage disturbance; after the new charging stage stabilizes, the reference efficiency is recalculated and the outer loop optimization logic is restored. After triggering the re-optimization, the second voltage perturbation step size is adopted, and the current input voltage is used as the initial value. Then, the process returns to step 2 until charging is completed. ② If no re-optimization is triggered, the system maintains the optimal input voltage and continues to monitor efficiency according to the preset cycle until charging is completed.

6. The maximum efficiency tracking control method according to claim 5, characterized in that: During the execution of the maximum efficiency tracking control method, both the input voltage and duty cycle are limited by preset safety limits. When any variable reaches its limit, or when battery overvoltage, overcurrent, communication interruption, or sampling abnormality occurs, the system suspends maximum efficiency tracking, maintains or reduces the input power, and the secondary side constant current / constant voltage control inner loop or system safety protection mechanism prioritizes the execution of safety control.

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