Optimal efficiency control method of bidirectional bilateral LCC induction type wireless charger

Abstract

The invention relates to the technical field of power electronic optimization control, and particularly discloses a self-adaptive optimal efficiency control method for a bidirectional bilateral LCC constant-power induction type wireless charger, and the method comprises the steps: estimating a coupling coefficient of a wireless charging coupler before charging is started; coupling coefficients are discretized during off-line calculation, optimal control parameters under the discrete coupling coefficients are solved, a lookup table is formed and stored in a secondary side controller, so that the optimal efficiency is still kept and constant-power charging or maximum-power tracking is realized even under the condition that a coupler deviates; according to the invention, the bidirectional bilateral LCC constant power induction type wireless charger can still maintain high average output power and efficiency during offset.

Description

Technical Field

[0001] This invention relates to the field of power electronics optimization control technology, specifically to an adaptive constant power optimal efficiency control method for a bidirectional, bilateral LCC constant power inductive wireless charger. Background Technology

[0002] The DS-LCC compensated topology not only solves the safety issue but also supports bidirectional power transfer. Due to this key advantage, the DS-LCC topology is widely used in IPT systems and has been adopted by industry standards. However, traditional DS-LCC wireless chargers are only constant current (CC) chargers. To achieve constant power (CP) charging functionality in DS-LCC wireless chargers, the prior art, "Wireless Electric Vehicle Charging," IEEE Transactions on Industrial Electronics, Vol. 70, No. 1, pp. 709-720, proposes a DS-LCC charger containing two switched control capacitors (SCCs). While this method successfully achieves constant power charging, the reliance on multiple SCCs also introduces some drawbacks, including increased device cost and additional power loss. The prior art, "The 9th International Conference on Green Energy and Applications (ICGEA) 2025," Singapore, 2025, pp. 1-5, proposes a constant power optimal efficiency control (CPOEC) strategy suitable for DS-LCC bidirectional wireless chargers. The ACPOEC strategy is based on three-phase shift (TPS) modulation and utilizes a pre-calculated lookup table obtained through offline optimization to achieve constant power charging while reaching the corresponding optimal efficiency. However, this method lacks adaptability; when the electromagnetic coupler shifts, the charging efficiency will deviate from the set optimal operating point, resulting in an overall decrease in charging power and efficiency. Therefore, it is necessary to design an adaptive optimal efficiency control method for a bidirectional, bilateral LCC constant power inductive wireless charger to address the problems of high charger cost, large power loss, and decreased charging power and efficiency in existing technologies. Summary of the Invention

[0003] To address the problems existing in the prior art, the purpose of this invention is to provide an adaptive constant power optimal efficiency control method for a bidirectional bilateral LCC inductive wireless charger.

[0004] The technical solution adopted by this invention to solve its technical problem is: an optimal efficiency control method for a bidirectional, double-sided LCC inductive wireless charger, comprising the following steps:

[0005] S1. The layout and construction of a constant power wireless charging system: the transmitting end system is equipped with an inverter, and the receiving end system is equipped with an active full-bridge rectifier.

[0006] S2. The phase difference between the fundamental components of the primary and secondary voltages is denoted as δ, and a phase shift compensation angle Δδ is introduced.

[0007] S3. Parameter estimation strategy for coupling coefficient k: A current sensor is installed on the receiving end to measure the current I. L2 Experimental measurements were conducted under different coupling coefficients k, and a lookup table was obtained. This lookup table was stored in the controller and used to measure the current I before each charging start. L2 Estimate the value of the coupling coefficient k;

[0008] S4. Constant power charger control strategy: The receiving end is equipped with a secondary controller and a battery voltage sensor. The secondary controller extracts the optimal duty cycle D based on the voltage measurement value from the battery voltage sensor and a pre-made lookup table. s_opt and the optimal phase shift compensation angle Δδ opt These two control parameters will be sent to the phase synchronization and pulse modulator in the secondary controller, which will then modulate the active rectifier based on these parameters. Simultaneously, the secondary controller will also determine the optimal duty cycle D of the primary side. p_opt Extracted and transmitted wirelessly to the main edge controller;

[0009] S5. The optimal variable in the lookup table is generated offline based on the established loss model.

[0010] Specifically, the inverter of the constant power wireless charging system in step S1 includes MOSFETs S1, S2, S3, and S4, which are used to generate AC voltage to drive the resonant circuit. The transmitter also includes a series inductor L1, a parallel capacitor C1, and a series compensation capacitor C. p , Primary coil self-inductance L p Internal resistance R LP And its input DC voltage V1, the inverter's output voltage and current are respectively expressed as u ab and i L1 .

[0011] Specifically, the rectifier of the constant power wireless charging system in step S1 includes MOSFETs S5, S6, S7, and S8, which are used to convert AC power into DC power. The receiver also includes a series inductor L2, a parallel capacitor C2, and a series compensation capacitor C. s DC bus capacitor C O Secondary coil self-inductance L s Coil resistance R LS And battery voltage V2, DC bus capacitance C O For voltage stabilization, the input voltage and current of the rectifier are expressed as u. cd and i L2 .

[0012] Specifically, the self-inductance L of the primary coil p and secondary coil self-inductance Ls Let the mutual inductance between them be M, and the coupling coefficient k be:

[0013]

[0014] Output voltage u ab The fundamental component is the variable u p Input voltage u cd The fundamental component is the variable u s u p and u s If the phase difference is δ, then the phase shift compensation angle is: Δδ=δ-π / 2;

[0015] The constant power wireless charging system ensures that each switch operates under zero-voltage switching (ZVS) conditions, with optimal phase shift compensation angle Δδ. opt The expression is:

[0016] Δδ opt =-D S π / 2+cos -1 {Λ -1 ×[-2πωL1L2I ZVS +V2L1(D S π 2 -8sin 2 (D S π / 2))]};

[0017] Where Λ=8MV1 sin(πD) P / 2), I ZVS It is the preset ZVS current threshold used to charge and discharge the equivalent output capacitor of the MOSFET during the dead time.

[0018] The formula for calculating transmission power P is: P = M / (ωL1L2)|U P ||U S |sin(π / 2+Δδ).

[0019] Specifically, in step S3, before the constant power wireless charging system starts charging, MOSFETs S7 and S8 are closed, and the input voltage u cd =0, ignoring losses in the wireless charger, measure the current I. L2 The relationship between the coupling coefficient k and the coupling coefficient k satisfies:

[0020]

[0021] Measuring current I L2 It is proportional to the coupling coefficient k, therefore, by measuring the current I... L2 The value of k is used to estimate the coupling coefficient k.

[0022] Specifically, the optimization objective of the offline optimization algorithm in step S5 is to select the optimal control variable to maximize efficiency within different battery voltage ranges while ensuring constant output power. To obtain maximum efficiency, a loss model is established, and the total power loss is divided into inverter loss, resonant network loss, and rectifier loss. Inverter loss includes conduction loss and switching loss. Since all switching devices have achieved zero-voltage switching (ZVS), the switching loss is minimal and is ignored in the overall loss optimization.

[0023] Specifically, the inverter loss is expressed as: P inv =2R ON *I L1 2 ;

[0024] Rectifier losses are expressed as: P rec =2R ON *I L2 2 ;

[0025] The resonant network loss is expressed as:

[0026] P res =I P 2 *R L1 +I S 2 *R L2 +I LP 2 *(R LP +R CP )+I LS 2 *(R LS +R CS )+I C1 2 *R C1 +I C2 2 *R C2 Among them, R CP R CS R C1 and R C2 Representing capacitor C P C S The equivalent series resistance (ESR) of C1 and C2;

[0027] Therefore, the total power loss of the charger is expressed as: P I =P inv +P rec +P res .

[0028] Specifically, the offline optimization algorithm based on the loss model includes the following steps:

[0029] S51. Initialization: Provide system parameters, input DC voltage V1, and coupling coefficient range k. min to k max Battery voltage range V 2min To V 2max and reference power P ref ;

[0030] S52. Discretization of coupling coefficient k: Sample the coupling coefficient k within a predetermined range with an appropriate step size;

[0031] S53, Discretization of battery voltage V2: Sample battery voltage V2 within a predetermined range with an appropriate step size;

[0032] S54. Control variable search for constant power charging: If the calculated power is different from the reference power P ref If the control variables are consistent within the tolerance e, then the corresponding control variables are retained; if the optimal duty cycle D... s_opt The optimal duty cycle D of the main side controller p_opt All have reached their maximum value of 1, and the transmission power still does not meet the reference power P. ref Then keep D. p_opt =D s_opt =1 and the corresponding optimal phase shift Δδ opt It is used to track the maximum power that can be transmitted at optimal efficiency;

[0033] S55. Variable optimization to achieve maximum efficiency: By comparing the calculated power losses, the combination with the minimum loss is selected to determine the optimal combination of control variables.

[0034] The present invention has the following beneficial effects:

[0035] The present invention presents an optimal efficiency control method for a bidirectional, double-sided LCC inductive wireless charger. In this strategy, the charging controller estimates the coupling coefficient of the magnetic field coupler and finds the corresponding control parameters in a pre-calculated lookup table based on the coupling coefficient. This ensures that even when the coupler is offset, the optimal efficiency is maintained and constant power charging or maximum power tracking is achieved. The charger also maintains a high average output power and efficiency even when offset. Attached Figure Description

[0036] Figure 1 This is a topology diagram of a constant power wireless charger.

[0037] Figure 2 This is a schematic diagram of the coupling coefficient parameter estimation strategy.

[0038] Figure 3 This is a block diagram of the control strategy for a constant power wireless charger.

[0039] Figure 4 This is a flowchart of the offline optimization method. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0041] like Figures 1-4 As shown, an adaptive optimal efficiency control method for a bidirectional, bilateral LCC constant power inductive wireless charger includes the following steps.

[0042] 1. For example Figure 1 As shown, the layout of the constant power wireless charging system is as follows: the transmitting end system is equipped with an inverter, and the receiving end system is equipped with an active full-bridge rectifier.

[0043] The inverter of the constant power wireless charging system includes MOSFETs S1, S2, S3, and S4, which generate AC voltage to drive the resonant circuit. The transmitter also includes a series inductor L1, a parallel capacitor C1, and a series compensation capacitor C. p , Primary coil self-inductance L p Internal resistance R LP And its input DC voltage V1, the inverter's output voltage and current are respectively expressed as u ab and i L1 .

[0044] The rectifier of the constant power wireless charging system includes MOSFETs S5, S6, S7, and S8, which are used to convert AC power to DC power. The receiver also includes a series inductor L2, a parallel capacitor C2, and a series compensation capacitor C. s DC bus capacitor C O Secondary coil self-inductance L s Coil resistance R LS And battery voltage V2, DC bus capacitance C O For voltage stabilization, the input voltage and current of the rectifier are expressed as u. cd and i L2 .

[0045] The self-inductance L of the primary coil p and secondary coil self-inductance L s Let the mutual inductance between them be M, and the coupling coefficient k be:

[0046] Because of the symmetrical topology of this system, it has bidirectional operation capability. Output voltage u ab The fundamental component is the variable u p Input voltage u cd The fundamental component is the variable u s u p and u s If the phase difference is δ, then the phase shift compensation angle is: Δδ=δ-π / 2.

[0047] To ensure that each switch in the constant power wireless charging system operates under ZVS conditions, the optimal phase shift Δδ is... opt The expression is:

[0048] Δδ opt =-D S π / 2+cos -1 {Λ -1 ×[-2πωL1L2I ZVS +V2L1(D S π 2 -8sin 2 (D S π / 2))]}.

[0049] Where Λ=8MV1sin(πD) P / 2), I ZVS It is a preset ZVS current threshold used to charge and discharge the equivalent output capacitor of the MOSFET during the dead time.

[0050] The formula for calculating transmission power P is: P = M / (ωL1L2)|U P ||U S |sin(π / 2+Δδ).

[0051] 2. For example Figure 2 As shown, the coupling coefficient k is calculated, the phase difference δ is calculated from the fundamental component of the input voltage, the phase shift compensation angle Δδ is introduced, and then the optimal phase shift Δδ is calculated. opt and transmission power P.

[0052] Before charging begins, the constant power wireless charging system closes MOSFETs S7 and S8, short-circuiting points C and D, thus reducing the input voltage u. cd =0, ignoring losses in the wireless charger, measure the current I. L2 The relationship between the coupling coefficient k and the coupling coefficient k satisfies:

[0053] This equation shows that the measured current I L2 It is proportional to the coupling coefficient k, therefore, by measuring the current I... L2 The value of k is used to estimate the coupling coefficient k.

[0054] 3. Parameter estimation strategy for coupling coefficient k: Set the measurement current I on the receiving end side. L2 Measuring current I L2 Experimental measurements were conducted under different coupling coefficients k, and a lookup table was obtained. This lookup table was stored in the controller and used to measure the current I before each charging start. L2 Estimate the value of the coupling coefficient k.

[0055] 4. For example Figure 3 As shown, the constant power charger control strategy involves a secondary controller at the receiving end. This secondary controller, based on the acquired battery voltage V2 and the estimated coupling coefficient k before charging, extracts the optimal duty cycle D using a pre-prepared lookup table. s_opt and optimal phase shift Δδ opt These two control parameters will be sent to the phase synchronization and pulse modulator in the secondary controller, which will then modulate the active rectifier based on these parameters. Simultaneously, the secondary controller will also determine the optimal duty cycle D of the primary side. p_opt It is extracted and sent to the main controller via wireless communication.

[0056] 5. For example Figure 4 As shown, the optimal variable in the lookup table is generated through an offline optimization algorithm to establish a loss model.

[0057] The optimization goal of the offline optimization algorithm is to select the optimal control variables to maximize efficiency within different battery voltage ranges while ensuring constant output power. To obtain the maximum efficiency, a loss model is established. The total power loss is divided into inverter loss, resonant network loss, and rectifier loss. Inverter loss includes conduction loss and switching loss. Since all switching devices have achieved zero-voltage switching (ZVS), the switching loss is minimal and is ignored in the overall loss optimization.

[0058] Inverter losses are expressed as: P inv =2R ON *I L1 2 ;

[0059] Rectifier losses are expressed as: P rec =2R ON *I L2 2 ;

[0060] The resonant network loss is expressed as:

[0061] P res =I P 2 *R L1 +I S2 *R L2 +I LP 2 *(R LP +R CP )+I LS 2 *(R LS +R CS )+I C1 2 *R C1 +I C2 2 *R C2 Among them, R CP R CS R C1 and R C2 Representing capacitor C P C S The equivalent series resistance (ESR) of C1 and C2;

[0062] Therefore, the total power loss of the charger is expressed as: P I =P inv +P rec +P res .

[0063] The offline optimization algorithm based on the loss model specifically includes the following steps:

[0064] (1) Initialization: Provide system parameters, input DC voltage V1, coupling coefficient range k min to k max Battery voltage range V 2min To V 2max and reference power P ref .

[0065] (2) Discretization of coupling coefficient k: Sample the coupling coefficient k within a predetermined range with an appropriate step size.

[0066] (3) Discretization of battery voltage V2: Sample battery voltage V2 within a predetermined range with an appropriate step size.

[0067] (4) Search for control variables for constant power charging: If the calculated power is different from the reference power P ref If the control variables are consistent within the tolerance e, then the corresponding control variables are retained; if the optimal duty cycle D... s_opt The optimal duty cycle D of the main side controller p_opt All have reached their maximum value of 1, and the transmission power still does not meet the reference power P. ref Then keep D. p_opt =D s_opt =1 and the corresponding optimal phase shift Δδ optIt is used to track the maximum power that can be transmitted at optimal efficiency.

[0068] (5) Variable optimization to achieve maximum efficiency: By comparing the calculated power losses, the combination with the smallest loss is selected to determine the optimal combination of control variables.

[0069] This invention is not limited to the above-described embodiments. Anyone should know that any structural changes made under the guidance of this invention, and any technical solutions that are the same as or similar to this invention, fall within the protection scope of this invention.

[0070] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. An optimal efficiency control method for a bidirectional, bilateral LCC inductive wireless charger, characterized in that, Includes the following steps: S1. The layout and construction of a constant power wireless charging system: the transmitting end system is equipped with an inverter, and the receiving end system is equipped with an active full-bridge rectifier. S2. The phase difference between the fundamental components of the primary and secondary voltages is denoted as δ, and a phase shift compensation angle Δδ is introduced. S3. Parameter estimation strategy for coupling coefficient k: A current sensor is installed on the receiving end to measure the current I. L2 Experimental measurements were conducted under different coupling coefficients k, and a lookup table was obtained. This lookup table was stored in the controller and used to measure the current I before each charging start. L2 Estimate the value of the coupling coefficient k; S4. Constant power charger control strategy: The receiving end is equipped with a secondary controller and a battery voltage sensor. The secondary controller extracts the optimal duty cycle D based on the voltage measurement value from the battery voltage sensor and a pre-made lookup table. s_opt and the optimal phase shift compensation angle Δδ opt These two control parameters will be sent to the phase synchronization and pulse modulator in the secondary controller, which will then modulate the active rectifier based on these parameters. Simultaneously, the secondary controller will also determine the optimal duty cycle D of the primary side. p_opt Extracted and transmitted wirelessly to the main edge controller; S5. The optimal variable in the lookup table is generated offline based on the established loss model.

2. The optimal efficiency control method for a bidirectional, bilateral LCC inductive wireless charger according to claim 1, characterized in that, The inverter of the constant power wireless charging system in step S1 includes MOSFETs S1, S2, S3, and S4, which are used to generate AC voltage to drive the resonant circuit. The transmitter also includes a series inductor L1, a parallel capacitor C1, and a series compensation capacitor C. p , Primary coil self-inductance L p Internal resistance R LP And its input DC voltage V1, the inverter's output voltage and current are respectively expressed as u ab and i L1 .

3. The optimal efficiency control method for a bidirectional, bilateral LCC inductive wireless charger according to claim 2, characterized in that, The rectifier of the constant power wireless charging system in step S1 includes MOSFETs S5, S6, S7, and S8, which are used to convert AC power into DC power. The receiver also includes a series inductor L2, a parallel capacitor C2, and a series compensation capacitor C. s DC bus capacitor C O Secondary coil self-inductance L s Coil resistance R LS And battery voltage V2, DC bus capacitance C O For voltage stabilization, the input voltage and current of the rectifier are expressed as u. cd and i L2 .

4. The optimal efficiency control method for a bidirectional, bilateral LCC inductive wireless charger according to claim 3, characterized in that, The self-inductance L of the primary coil p and secondary coil self-inductance L s Let the mutual inductance between them be M, and the coupling coefficient k be: Output voltage u ab The fundamental component is the variable u p Input voltage u cd The fundamental component is the variable u s u p and u s If the phase difference is δ, then the phase shift compensation angle is: Δδ=δ-π / 2; The constant power wireless charging system ensures that each switch operates under zero-voltage switching (ZVS) conditions, with optimal phase shift compensation angle Δδ. opt The expression is: Dd opt =-D S pi / 2+cos -1 {L -1 ×[-2πωL1L2I ZVS +V2L1(D S p 2 -8sin 2 (D S π / 2))]}; Where Λ=8MV1sin(πD) P / 2), I ZVS It is the preset ZVS current threshold used to charge and discharge the equivalent output capacitor of the MOSFET during the dead time. The formula for calculating transmission power P is: P = M / (ωL1L2)|U P ||U S |sin(π / 2+Δδ).

5. The optimal efficiency control method for a bidirectional, bilateral LCC inductive wireless charger according to claim 3, characterized in that, In step S3, before charging begins, MOSFETs S7 and S8 are closed, and the input voltage u... cd =0, ignoring losses in the wireless charger, measure the current I. L2 The relationship between the coupling coefficient k and the coupling coefficient k satisfies: Measuring current I L2 It is proportional to the coupling coefficient k, therefore, by measuring the current I... L2 The value of k is used to estimate the coupling coefficient k.

6. The optimal efficiency control method for a bidirectional, bilateral LCC inductive wireless charger according to claim 1, characterized in that, The optimization objective of the offline optimization algorithm in step S5 is to select the optimal control variable to maximize efficiency within different battery voltage ranges while ensuring constant output power. To obtain maximum efficiency, a loss model is established, and the total power loss is divided into inverter loss, resonant network loss, and rectifier loss. Inverter loss includes conduction loss and switching loss. Since all switching devices have achieved zero-voltage switching (ZVS), the switching loss is minimal and is ignored in the overall loss optimization.

7. The optimal efficiency control method for a bidirectional, bilateral LCC inductive wireless charger according to claim 6, characterized in that, The inverter loss is expressed as: P inv =2R ON *I L1 2 ; Rectifier losses are expressed as: P rec =2R ON *I L2 2 ; The resonant network loss is expressed as: P res =I P 2 *R L1 +I S 2 *R L2 +I LP 2 *(R LP +R CP )+I LS 2 *(R LS +R CS )+I C1 2 *R C1 +I C2 2 *R C2 ; Among them, R CP R CS R C1 and R C2 Representing capacitor C P C S The equivalent series resistance (ESR) of C1 and C2; Therefore, the total power loss of the charger is expressed as: P I =P inv +P rec +P res .

8. The optimal efficiency control method for a bidirectional, bilateral LCC inductive wireless charger according to claim 7, characterized in that, The offline optimization algorithm based on the loss model specifically includes the following steps: S51. Initialization: Provide system parameters, input DC voltage V1, and coupling coefficient range k. min to k max Battery voltage range V 2min To V 2max and reference power P ref ; S52. Discretization of coupling coefficient k: Sample the coupling coefficient k within a predetermined range with an appropriate step size; S53, Discretization of battery voltage V2: Sample battery voltage V2 within a predetermined range with an appropriate step size; S54. Control variable search for constant power charging: If the calculated power is different from the reference power P ref If the control variables are consistent within the tolerance e, then the corresponding control variables are retained; if the optimal duty cycle D... s_opt The optimal duty cycle D of the main side controller p_opt All have reached their maximum value of 1, and the transmission power still does not meet the reference power P. ref Then keep D. p_opt =D s_opt =1 and the corresponding optimal phase shift Δδ opt It is used to track the maximum power that can be transmitted at optimal efficiency; S55. Variable optimization to achieve maximum efficiency: By comparing the calculated power losses, the combination with the minimum loss is selected to determine the optimal combination of control variables.

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