Energy efficiency control method and device for wireless power transmission system

Abstract

The present invention provides a method and device for controlling the energy efficiency of a wireless power transmission system, the method comprising: under the condition that the parameters of the wireless power transmission system change, by adjusting the inverter parameters, the energy efficiency control of the wireless power transmission system is realized; wherein the wireless power transmission system parameters include one or more of the following parameters: compensation parameters; mutual inductance parameters; load parameters; the inverter parameters include one or more of the following parameters: operating frequency; phase shift angle; input voltage. The method and device for controlling the energy efficiency of a wireless power transmission system provided by the present invention adjust the operating frequency, input voltage or phase shift angle to control the energy efficiency of the wireless power transmission system on the basis of considering the system coupling and the compensation parameter deviation, so as to achieve the highest system transmission efficiency and better optimization effect.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transmission systems, and in particular to a method and device for controlling energy efficiency of wireless power transmission systems. Background Art

[0002] Due to the high-order nonlinearity and parameter complexity of the Wireless Power Transmission (WPT) system, the power-efficiency characteristics of the system and the working state of the device are easily affected when the coupling and compensation parameters and the load power demand change. Therefore, the control strategy should have a wide power adjustment range to adapt to different operating conditions, and realize efficient and stable operation of the system based on the changes in coupling and resonance parameters.

[0003] The principle of efficiency optimization is to achieve optimal load matching. For a coupling mechanism with a certain coupling coefficient, there is an optimal load resistance that maximizes efficiency. From the perspective of control methods, there are two main ways to achieve efficiency optimization: impedance matching and disturbance observation.

[0004] The principle of impedance matching is to keep the system equivalent load resistance as optimal as possible by adjusting the primary or secondary converter. The current distribution strategy of the hybrid energy storage load system proposed in the prior art converts the optimal load into optimal power control, and only achieves efficiency optimization by controlling the secondary DC / DC duty cycle. However, this method is only applicable to scenarios where the output power is constant and the load is a hybrid energy storage system.

[0005] The principle of the perturbation observation method is similar to the maximum power tracking strategy in photovoltaic converters, that is, the secondary converter adjusts the output voltage and current, changes the primary control quantity and continuously measures the transmission efficiency or input power / current, so that the system works at the maximum transmission efficiency point. This method is highly scalable and suitable for various topologies, but due to the coupling between the primary and secondary sides, the dynamic response characteristics are poor, the trial and error process may cause a large shock or drop in the output voltage, and bilateral communication is required.

[0006] At the same time, in order to reduce electromagnetic interference and improve the transmission efficiency of the converter, the switching device should achieve zero voltage switching (Zero Voltage Switching, ZVS).

[0007] The existing control strategies fail to take into account the efficiency in a wide coupling coefficient and wide output power range and the inverter ZVS operating characteristics. The coupling relationship between variables such as the WPT system coupling coefficient, load conditions and operating frequency and the transmission efficiency and ZVS operating characteristics needs further study. Due to the lack of systematic and accurate evaluation of the impact of compensation parameter deviation, the above control strategies have failed to solve the efficiency optimization problem when the compensation parameters have deviations, resulting in poor efficiency optimization of the WPT system. Summary of the invention

[0008] In view of the problems existing in the prior art, an embodiment of the present invention provides a method and device for controlling energy efficiency of a wireless power transmission system.

[0009] The present invention provides a method for controlling energy efficiency of a wireless power transmission system, comprising:

[0010] Under the condition that the parameters of the wireless power transmission system change, the energy efficiency of the wireless power transmission system can be controlled by adjusting the inverter parameters;

[0011] The wireless power transmission system parameters include one or more of the following parameters:

[0012] Compensation parameters;

[0013] Mutual inductance parameters;

[0014] Load parameters;

[0015] The inverter parameters include one or more of the following parameters:

[0016] Operating frequency;

[0017] Phase shift angle;

[0018] Input voltage.

[0019] In some embodiments, the energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including:

[0020] By adjusting the operating frequency of the inverter, energy efficiency control of the wireless power transmission system can be achieved.

[0021] In some embodiments, the energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including:

[0022] By adjusting the phase shift angle of the inverter, energy efficiency control of the wireless power transmission system can be achieved.

[0023] In some embodiments, the energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including:

[0024] Energy efficiency control of the wireless power transmission system is achieved by adjusting the operating frequency of the inverter and the phase shift angle of the inverter.

[0025] In some embodiments, the energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including:

[0026] By adjusting the input voltage of the inverter, energy efficiency control of the wireless power transmission system can be achieved.

[0027] In some embodiments, the energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including:

[0028] By adjusting the operating frequency of the inverter and the input voltage of the inverter, energy efficiency control of the wireless power transmission system can be achieved.

[0029] The present invention also provides an energy efficiency control device for a wireless power transmission system, comprising:

[0030] A control module, used to achieve energy efficiency control of the wireless power transmission system by adjusting inverter parameters under the condition that the parameters of the wireless power transmission system change;

[0031] The wireless power transmission system parameters include one or more of the following parameters:

[0032] Compensation parameters;

[0033] Mutual inductance parameters;

[0034] Load parameters;

[0035] The inverter parameters include one or more of the following parameters:

[0036] Operating frequency;

[0037] Phase shift angle;

[0038] Input voltage.

[0039] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the program, the energy efficiency control method of the wireless power transmission system as described above is implemented.

[0040] The present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the energy efficiency control method of the wireless power transmission system as described in any one of the above is implemented.

[0041] The present invention also provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the computer program implements any of the above-mentioned methods for controlling energy efficiency of a wireless power transmission system.

[0042] The wireless power transmission system energy efficiency control method and device provided by the present invention adjust the operating frequency, input voltage or phase shift angle to control the energy efficiency of the wireless power transmission system on the basis of considering system coupling and compensating parameter deviation, so as to maximize the system transmission efficiency and achieve better optimization effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 It is a flow chart of a method for controlling energy efficiency of a wireless power transmission system provided by an embodiment of the present invention;

[0045] Figure 2 It is one of the energy efficiency control block diagrams of the wireless power transmission system provided by the embodiment of the present invention;

[0046] Figure 3 It is one of the energy efficiency control logic diagrams of the wireless power transmission system provided by the embodiment of the present invention;

[0047] Figure 4 This is the second block diagram of energy efficiency control of the wireless power transmission system provided by an embodiment of the present invention;

[0048] Figure 5 This is the second schematic diagram of the energy efficiency control logic of the wireless power transmission system provided by the embodiment of the present invention;

[0049] Figure 6 This is the third block diagram of energy efficiency control of the wireless power transmission system provided by an embodiment of the present invention;

[0050] Figure 7 This is the third schematic diagram of energy efficiency control logic of the wireless power transmission system provided by the embodiment of the present invention;

[0051] Figure 8 This is the fourth block diagram of energy efficiency control of the wireless power transmission system provided by an embodiment of the present invention;

[0052] Fig. 9 This is the fourth schematic diagram of energy efficiency control logic of the wireless power transmission system provided by the embodiment of the present invention;

[0053] Fig.10 This is the fifth block diagram of energy efficiency control of the wireless power transmission system provided by the embodiment of the present invention;

[0054] Fig.11 This is the fifth schematic diagram of energy efficiency control logic of the wireless power transmission system provided by the embodiment of the present invention;

[0055] Fig.12 is a schematic structural diagram of an energy efficiency control device for a wireless power transmission system provided by an embodiment of the present invention;

[0056] Fig.13 It is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] The terms "first", "second", etc. in the specification and claims of the present invention are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the terms used in this way are interchangeable under appropriate circumstances, so that the embodiments of the present invention can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first" and "second" are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0059] Figure 1 FIG. 1 is a flow chart of a method for controlling energy efficiency of a wireless power transmission system according to an embodiment of the present invention. Figure 1 As shown, the wireless power transmission system energy efficiency control method provided by the embodiment of the present invention includes:

[0060] Step 101: Under the condition that the parameters of the wireless power transmission system change, energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters;

[0061] The wireless power transmission system parameters include one or more of the following parameters:

[0062] Compensation parameters;

[0063] Mutual inductance parameters;

[0064] Load parameters;

[0065] The inverter parameters include one or more of the following parameters:

[0066] Operating frequency;

[0067] Phase shift angle;

[0068] Input voltage.

[0069] Specifically, in some embodiments, the energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including:

[0070] By adjusting the operating frequency of the inverter, energy efficiency control of the wireless power transmission system can be achieved.

[0071] For example, Figure 2 is one of the energy efficiency control block diagrams of the wireless power transmission system provided by the embodiment of the present invention, such as Figure 2 As shown, the compensation device includes: primary parallel compensation capacitor C r , primary side series compensation capacitor C P , Secondary side series compensation capacitor C S and compensation inductor L r .

[0072] C r The corresponding compensation parameter is k Cr , which represents the ratio of the actual capacitance of the primary parallel compensation capacitor to its ideal value.

[0073] C P The corresponding compensation parameter is k CP , which represents the ratio of the actual capacitance of the primary series compensation capacitor to its ideal value.

[0074] C S The corresponding compensation parameter is k CS , which represents the ratio of the actual capacitance of the secondary side series compensation capacitor to its ideal value.

[0075] L r The corresponding compensation parameter is k Lr , which represents the ratio of the actual value of the primary series compensation inductance to its ideal value.

[0076] The mutual inductance parameter is k M , which represents the ratio of the actual value of mutual inductance to the ideal value.

[0077] The load parameter is k R , which represents the ratio of the actual value of the load resistance to the rated value.

[0078] The system operating frequency is ω, the ideal resonant frequency is ω0, k ω Represents the ratio of the secondary resonant frequency to the ideal resonant frequency, k ω2 It represents the ratio of the actual operating frequency to the secondary resonant frequency.

[0079] When the system is in resonance, the following relationship exists:

[0080]

[0081] Among them, L s Represents the self-inductance of the secondary coil, C S0 Represents the ideal value of the secondary side series compensation capacitor.

[0082] System impedance matching is crucial to improving the transmission efficiency of wireless power transmission systems. In actual systems, changes in output power, changes in mutual inductance caused by the position shift of the primary and secondary sides, and drift of compensation parameters will destroy the impedance matching relationship of the system and may lead to a decrease in transmission efficiency. By adjusting the frequency, in theory, the equivalent load resistance can be adjusted to the optimal load resistance as much as possible to achieve the purpose of efficiency optimization control.

[0083] This embodiment will analyze the impact of operating frequency adjustment on system transmission efficiency based on changes in output power, mutual inductance and compensation parameters.

[0084] Among the three parts of the inverter, coupling and compensation mechanism and secondary rectifier, although the loss proportion of the inverter and secondary rectifier cannot be ignored, there are fewer factors that affect the efficiency of the converter, only frequency, switching current and on-state current. The factors that affect the working state of the coupling and compensation mechanism include frequency, compensation parameters, mutual inductance and load parameters. The efficiency change of the coupling and compensation mechanism caused by poor impedance matching is more obvious. In addition, the main loss source of the primary inverter is switching loss. Accurate calculation of switching loss requires phase shift angle and switching current information, which will significantly increase the complexity of impedance matching relationship calculation, which is not conducive to engineering implementation. Therefore, considering the efficiency change and the difficulty of implementation, only the coupling and compensation mechanism is considered when deriving the optimal load resistance below.

[0085] When the frequency conversion and coupling and compensation parameters deviate, the current I S The expression is as follows:

[0086]

[0087] Among them, a, b, c, d, and g1 are all intermediate variables, U S0 represents the output voltage of the system when only the mutual inductance changes, δ represents the preset phase shift angle, which is generally set to π to fully utilize the current carrying capacity of the power conversion device, and R E0 The ideal value of the equivalent load resistance at the rectifier input, Q in Represents the load quality factor of the primary inverter, k R It represents the ratio of the actual value of the load resistance to the rated value, and Q0 represents the load quality factor of the secondary side of the coupling mechanism.

[0088] The expressions of a, b, c, d, and g1 are as follows:

[0089]

[0090] When the system operating frequency is the actual operating frequency, the ratio of the system output power to the rated power is k Po for:

[0091]

[0092] When there are deviations in output power, mutual inductance and compensation parameters, the transmission efficiency of the coupling and compensation mechanism is:

[0093]

[0094] Among them, P LP Represents the power loss of the primary side of the coupling mechanism, P LS Represents the power loss on the secondary side of the coupling mechanism, P o Indicates output power, P Lr Indicates compensation for inductor loss, i S Represents the true value of the secondary coil current, i in Represents the true value of the primary inverter output current, i P Represents the true value of the primary coil current, i Cr Represents the true value of the current of the primary parallel compensation capacitor, P C Indicates the compensation capacitor loss.

[0095] g2 and g3 are intermediate variables, and their expressions are as follows:

[0096]

[0097] According to the ratio of the output power to the rated power of the wireless power transmission system, that is, according to formula (1-4), the output power is the preset power k Po P O When the load resistance first change coefficient k R , which is expressed as follows:

[0098]

[0099] Among them, the expression of g4 is as follows:

[0100]

[0101] In formula (1-9), let Then when h1 meets the following conditions, the power demand of the load can be met.

[0102]

[0103] Substituting equation (1-8) into equation (1-5), we can find that the transmission efficiency becomes a univariate function only related to frequency. ω That is to say, the efficiency η is only related to the frequency change coefficient k. ω2This provides a theoretical basis for adjusting the frequency to optimize efficiency. At the same time, when the frequency changes, the impedance matching relationship of the system also changes, thereby changing the phase between the inverter output voltage and current, which may achieve ZVS operation of the inverter.

[0104] Therefore, by relying on the real parameters of the coupling and compensation mechanism obtained by online parameter estimation, the optimal efficiency control under ZVS conditions can be theoretically achieved by adjusting the frequency. Considering the tolerance of the system and the voltage and current tolerance of the device, in addition to the constraints shown in formula (1-10), the voltage and current of the compensation device should also be constrained. The voltage and current of the compensation device meet the third preset condition to ensure that the system can work safely.

[0105] The third precondition is as follows:

[0106]

[0107]

[0108] Among them, I in Indicates the effective value of the inverter output current, I Cr Indicates the compensation capacitor C r The effective value of the current, I P Indicates the compensation capacitor C P The effective value of the current, I S Indicates the compensation capacitor C s The effective value of the current, U Cr Indicates the compensation capacitor C r The effective value of the voltage, U CP Indicates the compensation capacitor C r The effective value of the voltage, U Cs Indicates the compensation capacitor C s The effective value of the voltage.

[0109] The subscript “-up” indicates the safety upper limit of the corresponding indicator.

[0110] Through the above method, the characteristic indicators of each link of the system can be calculated. The purpose of implementing the control strategy is to achieve comprehensive control of multiple objectives such as load power demand, ZVS operation of inverter switching devices and efficiency maximization on the basis of meeting the above constraints.

[0111] When the mutual inductance and compensation parameters are offset, the above three goals may not be met at the same time. In this state, the highest priority is given to meeting the load power demand. According to the characteristics of the switching device, when the inverter does not achieve ZVS operation, its transmission efficiency will drop significantly and electromagnetic interference will be generated. Therefore, the second priority of the control strategy is to achieve ZVS operation of the inverter switching device. Finally, the control strategy should maximize efficiency on the basis of meeting the above goals.

[0112] On the other hand, after the system design is completed, the maximum heat dissipation capacity of the device has been determined. A significant decrease in efficiency will mean that the proportion of power lost in the circuit will increase, which may cause thermal failure of the system, reduce the life of the device, and even cause safety accidents. Therefore, it is also necessary to limit the power loss of the system, which is closely related to the specific design of the system.

[0113] In order to maintain the scalability of theoretical analysis, this embodiment limits the lower limit of the transmission efficiency, as shown in formula (1-18), that is, when the calculated system efficiency is not less than the lower limit value η low When , the system is considered to be able to operate normally, that is:

[0114] η≥η low (1-18)

[0115] If the coupling and compensation parameters deviate seriously and cannot meet the above control objectives and constraints, the system needs to operate at reduced power. At the same time, the components that need to be replaced are determined based on the estimated parameters to provide a basis for system maintenance.

[0116] In summary, the control objective of the WPT system is multi-objective comprehensive optimization control under multiple constraints with the inverter switching frequency as the control variable.

[0117] In view of the limited computing power of the controller in the actual system, it is difficult to directly use the intelligent algorithm to find the optimal solution. In this paper, the switching frequency is discretized and the switching frequency is searched by traversal optimization. The step values ​​of the switching frequency are set to f g , the search range of the operating frequency is set to [f min , f max ].

[0118] Figure 3 is one of the energy efficiency control logic diagrams of the wireless power transmission system provided by the embodiment of the present invention, such as Figure 3 As shown in the figure, the specific process of traversal optimization is divided into the following steps:

[0119] Step 1: Initialize parameters and perform online parameter estimation.

[0120] Step 2: Initialize the operating frequency f to the search lower limit value f min .

[0121] Step 3: Determine whether the current frequency can meet the system power requirements. Calculate h1 according to formula (1-10), and decide whether to proceed to Step 4 based on the positive or negative value of h1.

[0122] If h1 is a non-negative number, it means that the system can output the expected power k at the current frequency. Po P O , go to Step 4 to continue calculation.

[0123] If h1 is a negative number, it means that the system cannot meet the load k at the current frequency. Po P O If the power requirement is met, the next operating frequency should be searched, that is, go to Step 5;

[0124] Step 4: Calculate the current and all constraints at the time the inverter is turned on at the current frequency, and record them.

[0125] Step 5: Increase the operating frequency to f+f g , if the increased operating frequency does not exceed the upper limit of the frequency range f max , then go to Step 3 to continue the calculation.

[0126] If the increased operating frequency exceeds the upper frequency limit, it means that the program has searched all optional frequencies. At this time, query the data record table to see if there is a parameter combination that meets the design objectives and constraints.

[0127] If so, select the most efficient implementation that meets the ZVS condition; if so, but none of them meets the ZVS condition, select the candidate with the smaller absolute value of current at the time of opening (for example, the absolute value of current at the time of opening is less than the preset value I op-limit The most efficient ones are selected to be implemented to minimize the impact of the opening time and maintain high efficiency.

[0128] If it does not exist, it means that the current system cannot guarantee the safe and stable output of the expected power due to the excessive deviation of the coupling and compensation parameters from the rated state. At this time, the expected output power should be reduced. Let the output power change ratio be k Po -k Po-g , and continue the calculation in Step 2 until a parameter combination that meets the design objectives and constraints is found. After the system stops working, the coupling and compensation parameters should be adjusted according to the results of the online parameter estimation to restore the system to the rated state.

[0129] The embodiments of the present invention achieve energy efficiency control of the wireless power transmission system by adjusting the operating frequency of the inverter, so that the system transmission efficiency is the highest and the optimization effect is better.

[0130] Specifically, in some embodiments, the energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including:

[0131] By adjusting the phase shift angle of the inverter, energy efficiency control of the wireless power transmission system can be achieved.

[0132] For example, Figure 4 This is the second block diagram of the energy efficiency control of the wireless power transmission system provided by the embodiment of the present invention, such as Figure 4 As shown, the compensation device includes: primary parallel compensation capacitor C r , primary side series compensation capacitor C P , Secondary side series compensation capacitor C S and compensation inductor L r .

[0133] C r The corresponding compensation parameter is k Cr , which represents the ratio of the actual capacitance of the primary parallel compensation capacitor to its ideal value.

[0134] C P The corresponding compensation parameter is k CP , which represents the ratio of the actual capacitance of the primary series compensation capacitor to its ideal value.

[0135] C S The corresponding compensation parameter is k CS , which represents the ratio of the actual capacitance of the secondary side series compensation capacitor to its ideal value.

[0136] L r The corresponding compensation parameter is k Lr , which represents the ratio of the actual value of the primary series compensation inductance to its ideal value.

[0137] The mutual inductance parameter is k M , which represents the ratio of the actual value of mutual inductance to the ideal value.

[0138] The load parameter is k R , which represents the ratio of the actual value of the load resistance to the rated value.

[0139] The system operating frequency is ω, the ideal resonant frequency is ω0, k ω Represents the ratio of the secondary resonant frequency to the ideal resonant frequency, k ω2 It represents the ratio of the actual operating frequency to the secondary resonant frequency.

[0140] When the system is in resonance, the following relationship exists:

[0141]

[0142] Among them, L s Represents the self-inductance of the secondary coil, CS0 Represents the ideal value of the secondary side series compensation capacitor.

[0143] System impedance matching is crucial to improving the transmission efficiency of wireless power transmission systems. In actual systems, changes in output power, changes in mutual inductance caused by the position shift of the primary and secondary sides, and drift of compensation parameters will destroy the impedance matching relationship of the system and may lead to a decrease in transmission efficiency. By adjusting the phase shift angle, the equivalent load resistance can theoretically be adjusted to the optimal load resistance as much as possible to achieve the purpose of efficiency optimization control.

[0144] This embodiment will analyze the influence of inverter phase shift angle adjustment on system transmission efficiency based on the changes of output power, mutual inductance and compensation parameters.

[0145] Among the three parts of the inverter, coupling and compensation mechanism and secondary rectifier, although the loss proportion of the inverter and secondary rectifier cannot be ignored, there are fewer factors that affect the efficiency of the converter, only frequency, switching current and on-state current. The factors that affect the working state of the coupling and compensation mechanism include frequency, compensation parameters, mutual inductance and load parameters. The efficiency change of the coupling and compensation mechanism caused by poor impedance matching is more obvious. In addition, the main loss source of the primary inverter is switching loss. Accurate calculation of switching loss requires phase shift angle and switching current information, which will significantly increase the complexity of impedance matching relationship calculation, which is not conducive to engineering implementation. Therefore, considering the efficiency change and the difficulty of implementation, only the coupling and compensation mechanism is considered when deriving the optimal load resistance below.

[0146] When the frequency conversion and coupling and compensation parameters deviate, the current I S The expression is as follows:

[0147]

[0148] Among them, a, b, c, d, and g1 are all intermediate variables, U S0 represents the output voltage of the system when only the mutual inductance changes, δ represents the inverter phase shift angle, and the allowable adjustment range is set to [δ min , δ max ], R E0 The ideal value of the equivalent load resistance at the rectifier input, Q in Represents the load quality factor of the primary inverter, k R It represents the ratio of the actual value of the load resistance to the rated value, and Q0 represents the load quality factor of the secondary side of the coupling mechanism.

[0149] The expressions of a, b, c, d, and g1 are as follows:

[0150]

[0151] When the system operating frequency is the actual operating frequency, the ratio of the system output power to the rated power is k Po for:

[0152]

[0153] When there are deviations in output power, mutual inductance and compensation parameters, the transmission efficiency of the coupling and compensation mechanism is:

[0154]

[0155] Among them, P LP Represents the power loss of the primary side of the coupling mechanism, P LS Represents the power loss on the secondary side of the coupling mechanism, P o Indicates output power, P Lr Indicates compensation for inductor loss, i S Represents the true value of the secondary coil current, i in Represents the true value of the primary inverter output current, i P Represents the true value of the primary coil current, i Cr Represents the true value of the current of the primary parallel compensation capacitor, P C Indicates the compensation capacitor loss.

[0156] g2 and g3 are intermediate variables, and their expressions are as follows:

[0157]

[0158]

[0159] According to the ratio of the output power to the rated power of the wireless power transmission system, that is, according to formula (2-4), the output power is the preset power k Po P O When the load resistance first change coefficient k R , which is expressed as follows:

[0160]

[0161] Among them, the expression of g4 is as follows:

[0162]

[0163] In formula (2-8), let Then when h1 meets the following conditions, the power demand of the load can be met.

[0164]

[0165] Substituting formula (2-8) into formula (2-5) and taking the derivative of the transmission efficiency with respect to the phase shift angle, it can be obtained that the phase shift angle δ at the extreme point satisfies the following formula:

[0166]

[0167] After numerical verification, g2, g3 and g4 are all positive numbers. Considering that the phase shift angle can only be min , δ max ] range, so when the phase shift angle δ satisfies the following formula (2-12), maximum efficiency control can be achieved by adjusting the phase shift angle.

[0168]

[0169] There is a complex coupling relationship between the coupling and compensation parameter deviation, inverter operating frequency and phase shift angle, system transmission power capacity, inverter device working state and transmission efficiency. Adjusting the phase shift angle will affect both the system power characteristics and the inverter's ZVS operating state. The influence law will also change when the parameter deviation state is different. The arbitrary reduction of the analysis and control dimensions will lead to defects in the system's comprehensive characteristics. Therefore, when formulating the control strategy, comprehensive consideration should be given from the system perspective to achieve efficient and stable operation within a wide parameter range of the system.

[0170] The transmission power, ZVS operation and efficiency characteristics of the system are affected by multiple factors such as load demand, coupling and compensation parameter deviation, and phase shift angle adjustment is an effective means to control the above characteristics. At the same time, due to the complex nonlinear coupling relationship between the phase shift angle, coupling and compensation parameters, and system efficiency characteristics, it is necessary to comprehensively consider factors such as transmission power capacity, inverter operating status, and transmission efficiency when selecting the phase shift angle.

[0171] Therefore, by relying on the real parameters of the coupling and compensation mechanism obtained by online parameter estimation, the optimal efficiency control under ZVS conditions can be theoretically achieved by adjusting the inverter phase shift angle. Considering the system tolerance and the voltage and current tolerance of the device, in addition to the constraints shown in formulas (2-10) and (2-12), the voltage and current of the compensation device should also be constrained. The voltage and current of the compensation device meet the third preset condition to ensure that the system can work safely.

[0172] The third precondition is as follows:

[0173]

[0174]

[0175] Among them, I in Indicates the effective value of the inverter output current, I Cr Indicates the compensation capacitor C rThe effective value of the current, I P Indicates the compensation capacitor C P The effective value of the current, I S Indicates the compensation capacitor C s The effective value of the current, U Cr Indicates the compensation capacitor C r The effective value of the voltage, U CP Indicates the compensation capacitor C r The effective value of the voltage, U Cs Indicates the compensation capacitor C s The effective value of the voltage.

[0176] The subscript “-up” indicates the safety upper limit of the corresponding indicator.

[0177] Through the above method, the characteristic indicators of each link of the system can be calculated. The purpose of implementing the control strategy is to achieve comprehensive control of multiple objectives such as load power demand, ZVS operation of inverter switching devices and efficiency maximization on the basis of meeting the above constraints.

[0178] When the mutual inductance and compensation parameters are offset, the above three goals may not be met at the same time. In this state, the highest priority is given to meeting the load power demand. According to the characteristics of the switching device, when the inverter does not achieve ZVS operation, its transmission efficiency will drop significantly and electromagnetic interference will be generated. Therefore, the second priority of the control strategy is to achieve ZVS operation of the inverter switching device. Finally, the control strategy should maximize efficiency on the basis of meeting the above goals.

[0179] On the other hand, after the system design is completed, the maximum heat dissipation capacity of the device has been determined. A significant decrease in efficiency will mean that the proportion of power lost in the circuit will increase, which may cause thermal failure of the system, reduce the life of the device, and even cause safety accidents. Therefore, it is also necessary to limit the power loss of the system, which is closely related to the specific design of the system.

[0180] In order to maintain the scalability of theoretical analysis, this embodiment limits the lower limit of the transmission efficiency, as shown in formula (2-20), that is, when the calculated system efficiency is not less than the lower limit value η low When , the system is considered to be able to operate normally, that is:

[0181] η≥η low (2-20)

[0182] If the coupling and compensation parameters deviate seriously and cannot meet the above control objectives and constraints, the system needs to operate at reduced power. At the same time, the components that need to be replaced are determined based on the estimated parameters to provide a basis for system maintenance.

[0183] In summary, the control objective of the WPT system is multi-objective comprehensive optimization control under multiple constraints with the inverter phase shift angle as the control variable.

[0184] Although the phase shift angle corresponding to the highest efficiency can be directly calculated according to formula (2-11), it is difficult to directly use intelligent algorithms to find the best solution due to the limited computing power of the controller in the actual system and the existence of many constraints. Here, the phase shift angle is discretized and the optimal phase shift angle is searched by traversal optimization. The step value of the phase shift angle is set to δ g , the search range of the phase shift angle is set to [δ min , δ max ], generally [0, π].

[0185] Figure 5 FIG. 2 is a second schematic diagram of energy efficiency control logic of a wireless power transmission system provided by an embodiment of the present invention. Figure 5 As shown in the figure, the specific process of traversal optimization is divided into the following steps:

[0186] Step 1: Initialize parameters and perform online parameter estimation.

[0187] Step 2: Initialize the phase shift angle δ to the search upper limit δ max .

[0188] Step 3: Determine whether the current phase shift angle can meet the system power demand. Calculate h1 according to formula (2-10), and decide whether to proceed to Step 4 based on the positive or negative value of h1.

[0189] If h1 is a non-negative number, it means that the system can output the expected power k under the current phase shift angle. Po P O , go to Step 4 to continue calculation.

[0190] If h1 is negative, it means that the system cannot meet the load k under the current parameters. Po P O The power demand is determined, and the process goes to Step 5;

[0191] Step 4: Determine whether there is an optimal phase shift angle under the current parameters. Calculate h2 according to formula (2-12) and determine whether h2 is within the allowable range.

[0192] If h2 is within the allowable range, it means that it is possible to achieve optimal load regulation under this parameter, and the calculation is continued in Step 6.

[0193] If h2 is not within the allowable range, it means that although the system can achieve the expected power output, it cannot be adjusted to the optimal load. At this time, the goal of traversal optimization becomes to find the most efficient parameter combination that meets ZVS and constraint conditions, and then go to Step 7;

[0194] Step 5: It indicates that the system cannot meet the load k under the current parameters. Po P O The power demand indicates that the current system cannot guarantee the safe and stable output of the expected power because the coupling and compensation parameters deviate too much from the rated state. At this time, the expected output power should be reduced. Let the output power change ratio be k Po -k Po-g , and continue the calculation in Step 2 until a parameter combination that meets the design objectives and constraints is found. After the system stops working, the coupling and compensation parameters should be adjusted according to the results of the online parameter estimation to restore the system to the rated state.

[0195] Step 6: Find the available phase shift angle. Calculate the optimal phase shift angle δ under the current parameters according to formula (2-11) opt , let the phase shift angle be δ = δ opt , and substitute it into formula (2-10) to calculate h1.

[0196] If h1≥0, it means that under this parameter, the system can achieve the expected power and optimal load operation at the same time, and the ZVS and constraint conditions are judged at this time.

[0197] If the ZVS operation and constraint conditions are met, it means that the phase shift angle can simultaneously meet the three control objectives and all constraint conditions. Record the set of parameters and adjust the phase shift angle to δ opt ;

[0198] If the ZVS operation and constraint conditions are not met, it is necessary to continue searching for an available phase shift angle. Under the same operating conditions, when the phase shift angle increases, the fundamental current at the device turn-on time will decrease, which is more conducive to achieving ZVS operation. On the other hand, when the phase shift angle increases, the current stress in the loop decreases under the same output power, which is conducive to the realization of the constraint conditions.

[0199] Therefore, the phase shift angle is δ opt , ZVS operation and when the constraint conditions are not met, δ g The step value increases, in [δ opt , δ max ] range to find the phase shift angle δ that meets the ZVS operation and constraint conditions.

[0200] If h1<0, it means that the expected power operation cannot be achieved with the optimal load under the current parameters. According to the principle of highest priority for output power, similarly, the phase shift angle should be gradually increased until h1≥0 and the ZVS operation and constraint conditions are met.

[0201] If such a phase shift angle exists, record this set of parameters and go to Step 8.

[0202] Step 7: Find an available phase shift angle. When other parameters are fixed and the phase shift angle is less than the optimal phase shift angle, the transmission efficiency of the coupling and compensation mechanism increases with the increase of the phase shift angle, and when the phase shift angle is greater than the optimal phase shift angle, the transmission efficiency decreases monotonically with the phase shift angle.

[0203] Therefore, when the difference between the phase shift angle and the optimal phase shift angle is the smallest, the system efficiency can reach the maximum value at the current frequency. Therefore, let the initial value of the phase shift angle be δ max , the decreasing step value is δ g , in [δ min , δ max ] range to search for a phase shift angle that meets the output power requirement, i.e., h1 ≥ 0 and satisfies the ZVS operation and constraint conditions.

[0204] If such a phase shift angle exists, it means that although this set of parameters does not achieve the optimal efficiency of the system, it can output the expected power, achieve ZVS operation and meet all constraints. Therefore, this set of parameters is recorded as a candidate and transferred to Step 8;

[0205] If there is no phase shift angle that meets the conditions, it means that all control objectives cannot be achieved on the basis of meeting the constraints at this frequency, and the process goes to Step 8.

[0206] Step 8: Check the data record table to see if there is any parameter combination that meets the design objectives and constraints.

[0207] If so, select the most efficient implementation that meets the ZVS condition; if so, but none of them meets the ZVS condition, select the candidate with the smaller absolute value of current at the time of opening (for example, the absolute value of current at the time of opening is less than the preset value I op-limit The most efficient ones are selected to be implemented to minimize the impact of the opening time and maintain high efficiency.

[0208] If it does not exist, it means that the current system cannot guarantee the safe and stable output of the expected power because the coupling and compensation parameters deviate too much from the rated state, and then go to Step 5 to continue the calculation.

[0209] The embodiment of the present invention realizes energy efficiency control of the wireless power transmission system by adjusting the phase shift angle of the inverter, so that the system transmission efficiency is the highest and the optimization effect is better.

[0210] Specifically, in some embodiments, the energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including:

[0211] Energy efficiency control of the wireless power transmission system is achieved by adjusting the operating frequency of the inverter and the phase shift angle of the inverter.

[0212] For example, Figure 6 This is the third block diagram of energy efficiency control of the wireless power transmission system provided by the embodiment of the present invention, such as Figure 6 As shown, the compensation device includes: primary parallel compensation capacitor C r , primary side series compensation capacitor C P , Secondary side series compensation capacitor C S and compensation inductor L r .

[0213] C r The corresponding compensation parameter is k Cr , which represents the ratio of the actual capacitance of the primary parallel compensation capacitor to its ideal value.

[0214] C P The corresponding compensation parameter is k CP , which represents the ratio of the actual capacitance of the primary series compensation capacitor to its ideal value.

[0215] C S The corresponding compensation parameter is k CS , which represents the ratio of the actual capacitance of the secondary side series compensation capacitor to its ideal value.

[0216] L r The corresponding compensation parameter is k Lr , which represents the ratio of the actual value of the primary series compensation inductance to its ideal value.

[0217] The mutual inductance parameter is k M , which represents the ratio of the actual value of mutual inductance to the ideal value.

[0218] The load parameter is k R , which represents the ratio of the actual value of the load resistance to the rated value.

[0219] The system operating frequency is ω, the ideal resonant frequency is ω0, k ω Represents the ratio of the secondary resonant frequency to the ideal resonant frequency, k ω2 It represents the ratio of the actual operating frequency to the secondary resonant frequency.

[0220] When the system is in resonance, the following relationship exists:

[0221]

[0222] Among them, L s Represents the self-inductance of the secondary coil, C S0 Represents the ideal value of the secondary side series compensation capacitor.

[0223] System impedance matching is crucial to improving the transmission efficiency of wireless power transmission systems. In actual systems, changes in output power, changes in mutual inductance caused by the position shift of the primary and secondary sides, and drift of compensation parameters will destroy the impedance matching relationship of the system and may lead to a decrease in transmission efficiency. By adjusting the frequency and phase shift angle, the equivalent load resistance can theoretically be adjusted to the optimal load resistance as much as possible to achieve the purpose of efficiency optimization control.

[0224] This embodiment will analyze the influence of the operating frequency and phase shift angle adjustment on the system transmission efficiency based on the changes in output power, mutual inductance and compensation parameters.

[0225] Among the three parts of the inverter, coupling and compensation mechanism and secondary rectifier, although the loss proportion of the inverter and secondary rectifier cannot be ignored, there are fewer factors that affect the efficiency of the converter, only frequency, switching current and on-state current. The factors that affect the working state of the coupling and compensation mechanism include frequency, compensation parameters, mutual inductance and load parameters. The efficiency change of the coupling and compensation mechanism caused by poor impedance matching is more obvious. In addition, the main loss source of the primary inverter is switching loss. Accurate calculation of switching loss requires phase shift angle and switching current information, which will significantly increase the complexity of impedance matching relationship calculation, which is not conducive to engineering implementation. Therefore, considering the efficiency change and the difficulty of implementation, only the coupling and compensation mechanism is considered when deriving the optimal load resistance below.

[0226] When the frequency conversion and coupling and compensation parameters deviate, the current I S The expression is as follows:

[0227]

[0228] Among them, a, b, c, d, and g1 are all intermediate variables, U S0 represents the output voltage of the system when only the mutual inductance changes, δ represents the inverter phase shift angle, and the allowable adjustment range is set to [δ min , δ max ], R E0 The ideal value of the equivalent load resistance at the rectifier input, Q in Represents the load quality factor of the primary inverter, k R It represents the ratio of the actual value of the load resistance to the rated value, and Q0 represents the load quality factor of the secondary side of the coupling mechanism.

[0229] The expressions of a, b, c, d, and g1 are as follows:

[0230]

[0231] When the system operating frequency is the actual operating frequency, the ratio of the system output power to the rated power is k Po for:

[0232]

[0233] When there are deviations in output power, mutual inductance and compensation parameters, the transmission efficiency of the coupling and compensation mechanism is:

[0234]

[0235] Among them, P LP Represents the power loss of the primary side of the coupling mechanism, P LS Represents the power loss on the secondary side of the coupling mechanism, P o Indicates output power, P Lr Indicates compensation for inductor loss, i S Represents the true value of the secondary coil current, i in Represents the true value of the primary inverter output current, i P Represents the true value of the primary coil current, i Cr Represents the true value of the current of the primary parallel compensation capacitor, P C Indicates the compensation capacitor loss.

[0236] g2 and g3 are intermediate variables, and their expressions are as follows:

[0237]

[0238] According to the ratio of the output power to the rated power of the wireless power transmission system, that is, according to formula (3-4), the output power is the preset power k Po P O When the load resistance first change coefficient k R , which is expressed as follows:

[0239]

[0240] Among them, the expression of g4 is as follows:

[0241]

[0242] In formula (3-8), let Then when h1 meets the following conditions, the power demand of the load can be met.

[0243]

[0244] Substituting formula (3-8) into formula (3-5) and taking the derivative of the transmission efficiency with respect to the phase shift angle, we can obtain that the phase shift angle δ at the extreme point satisfies the following formula:

[0245]

[0246] After numerical verification, g2, g3 and g4 are all positive numbers. Considering that the phase shift angle can only be min , δ max ] range, so when the phase shift angle δ satisfies the following formula (3-12), maximum efficiency control can be achieved by adjusting the frequency and phase shift angle.

[0247]

[0248] There is a complex coupling relationship between coupling and compensation parameter deviation, inverter operating frequency and phase shift angle, system transmission power capacity, inverter device working state and transmission efficiency. Adjusting the frequency and phase shift angle will affect the system power characteristics and the inverter's ZVS operating state at the same time. The influence law will also change when the parameter deviation state is different. The arbitrary reduction of the analysis and control dimensions will lead to defects in the comprehensive characteristics of the system. Therefore, when formulating the control strategy, comprehensive consideration should be given from the system perspective to achieve efficient and stable operation within a wide parameter range of the system.

[0249] The transmission power, ZVS operation and efficiency characteristics of the system are affected by multiple factors such as load demand, coupling and compensation parameter deviation, and frequency and phase shift angle adjustment are effective means to control the above characteristics. At the same time, due to the complex nonlinear coupling relationship between the phase shift angle, coupling and compensation parameters, and system efficiency characteristics, it is necessary to comprehensively consider factors such as transmission power capacity, inverter operating status, and transmission efficiency when selecting frequency and phase shift angle.

[0250] Therefore, by relying on the real parameters of the coupling and compensation mechanism obtained by online parameter estimation, the optimal efficiency control under ZVS conditions can be theoretically achieved by adjusting the inverter frequency and phase shift angle. Considering the system tolerance and the voltage and current tolerance of the device, in addition to the constraints shown in formulas (3-10) and (3-12), the voltage and current of the compensation device should also be constrained. The voltage and current of the compensation device meet the third preset condition to ensure that the system can work safely.

[0251] The third precondition is as follows:

[0252]

[0253] Among them, I in Indicates the effective value of the inverter output current, I Cr Indicates the compensation capacitor C r The effective value of the current, I P Indicates the compensation capacitor C P The effective value of the current, I S Indicates the compensation capacitor C s The effective value of the current, U Cr Indicates the compensation capacitor C r The effective value of the voltage, UCP Indicates the compensation capacitor C r The effective value of the voltage, U Cs Indicates the compensation capacitor C s The effective value of the voltage.

[0254] The subscript “-up” indicates the safety upper limit of the corresponding indicator.

[0255] Through the above method, the characteristic indicators of each link of the system can be calculated. The purpose of implementing the control strategy is to achieve comprehensive control of multiple objectives such as load power demand, ZVS operation of inverter switching devices and efficiency maximization on the basis of meeting the above constraints.

[0256] When the mutual inductance and compensation parameters are offset, the above three goals may not be met at the same time. In this state, the highest priority is given to meeting the load power demand. According to the characteristics of the switching device, when the inverter does not achieve ZVS operation, its transmission efficiency will drop significantly and electromagnetic interference will be generated. Therefore, the second priority of the control strategy is to achieve ZVS operation of the inverter switching device. Finally, the control strategy should maximize efficiency on the basis of meeting the above goals.

[0257] On the other hand, after the system design is completed, the maximum heat dissipation capacity of the device has been determined. A significant decrease in efficiency will mean that the proportion of power lost in the circuit will increase, which may cause thermal failure of the system, reduce the life of the device, and even cause safety accidents. Therefore, it is also necessary to limit the power loss of the system, which is closely related to the specific design of the system.

[0258] In order to maintain the scalability of theoretical analysis, this embodiment limits the lower limit of transmission efficiency, as shown in formula (3-20), that is, when the calculated system efficiency is not less than the lower limit value η low When , the system is considered to be able to operate normally, that is:

[0259] η≥η low (3-20)

[0260] If the coupling and compensation parameters deviate seriously and cannot meet the above control objectives and constraints, the system needs to operate at reduced power. At the same time, the components that need to be replaced are determined based on the estimated parameters to provide a basis for system maintenance.

[0261] In summary, the control objective of the WPT system is multi-objective comprehensive optimization control under multiple constraints with the inverter operating frequency and phase shift angle as control variables.

[0262] Although the phase shift angle corresponding to the highest efficiency can be directly calculated according to formula (3-11), it is difficult to directly use intelligent algorithms to find the best solution due to the limited computing power of the controller in the actual system and the existence of many constraints. Here, the frequency and phase shift angle are discretized and the optimal frequency and phase shift angle are searched by traversal optimization. The step values ​​of the switching frequency are set to f g , the search range of the operating frequency is set to [f min , f max ]. The step value of the phase shift angle is set to δ g , the search range of the phase shift angle is set to [δ min , δ max ], generally [0, π].

[0263] Figure 7 FIG. 3 is a third schematic diagram of energy efficiency control logic of a wireless power transmission system provided by an embodiment of the present invention. Figure 7 As shown in the figure, the specific process of traversal optimization is divided into the following steps:

[0264] Step 1: Initialize parameters and perform online parameter estimation.

[0265] Step 2: Initialize the operating frequency f to the search lower limit, here f min .

[0266] Step 3: Initialize the phase shift angle δ to δ max .

[0267] Step 4: Determine whether the current frequency can meet the system power requirements. Calculate h1 according to formula (3-10), and decide whether to proceed to Step 5 based on the positive or negative value of h1.

[0268] If h1 is a negative number, it means that the system cannot meet the load k at the current frequency. Po P O If the power requirement is met, the next operating frequency should be searched, that is, go to Step 5;

[0269] If h1 is a non-negative number, it means that at the current frequency, in [δ min , δ max ] there is a phase shift angle that enables the system to output the desired power k Po P O , go to Step 6 to continue calculation.

[0270] Step 5: Increase the operating frequency to f+f g , if the increased operating frequency does not exceed the upper limit of the frequency range f max , then go to Step 3 to continue the calculation.

[0271] If the increased operating frequency exceeds the upper frequency limit, it means that the program has searched all optional frequencies. At this time, query the data record table to see if there is a parameter combination that meets the design objectives and constraints.

[0272] If so, select the most efficient implementation that meets the ZVS condition; if so, but none of them meets the ZVS condition, select the candidate with the smaller absolute value of current at the time of opening (for example, the absolute value of current at the time of opening is less than the preset value I op-limit The most efficient ones are selected to be implemented to minimize the impact of the opening time and maintain high efficiency.

[0273] If it does not exist, it means that the current system cannot guarantee the safe and stable output of the expected power due to the excessive deviation of the coupling and compensation parameters from the rated state. At this time, the expected output power should be reduced. Let the output power change ratio be k Po -k Po-g , and continue the calculation in Step 2 until a parameter combination that meets the design objectives and constraints is found. After the system stops working, the coupling and compensation parameters should be adjusted according to the results of the online parameter estimation to restore the system to the rated state.

[0274] Step 6: Determine whether there is an optimal phase shift angle at the current frequency. Calculate h2 according to formula (3-10) and determine whether h2 is within the allowable range.

[0275] If h2 is not within the allowable range, it means that although the expected power output can be achieved at this frequency, it cannot be adjusted to the optimal load. At this time, the goal of the traversal optimization becomes to find the most efficient parameter combination that meets the ZVS and constraint conditions, and then go to Step 7;

[0276] If h2 is within the allowable range, it means that optimal load regulation can be achieved at this frequency, and the calculation can be continued in Step 8.

[0277] Step 7: Find an available phase shift angle. When other parameters are fixed and the phase shift angle is less than the optimal phase shift angle, the transmission efficiency of the coupling and compensation mechanism increases with the increase of the phase shift angle, and when the phase shift angle is greater than the optimal phase shift angle, the transmission efficiency decreases monotonically with the phase shift angle.

[0278] Therefore, when the difference between the phase shift angle and the optimal phase shift angle is the smallest, the system efficiency can reach the maximum value at the current frequency. Therefore, let the initial value of the phase shift angle be δ max , the decreasing step value is δ g , in [δ min , δ max ] range to search for a phase shift angle that meets the output power requirement, i.e., h1 ≥ 0 and satisfies the ZVS operation and constraint conditions.

[0279] If such a phase shift angle exists, it means that although this set of parameters does not achieve the optimal efficiency of the system, it can output the expected power, achieve ZVS operation and meet all constraints. Therefore, this set of parameters is recorded as a candidate and transferred to Step 5 to continue the calculation;

[0280] If there is no phase shift angle that meets the conditions, it means that all control objectives cannot be achieved at this frequency while meeting the constraints, and the next frequency point should be calculated and the process goes to Step 5.

[0281] Step 8: Find the available phase shift angle. Calculate the optimal phase shift angle δ at the current frequency according to formula (3-11) opt , let the phase shift angle be δ = δ opt , and substitute it into formula (3-10) to calculate h1.

[0282] If h1≥0, it means that at this frequency, the system can achieve both the expected power and the optimal load operation. At this time, the ZVS and constraint conditions are judged.

[0283] If the ZVS operation and constraint conditions are met, it means that the frequency and phase shift angle can simultaneously meet the three control objectives and all constraint conditions. Record this group of parameters and calculate the next frequency point, that is, go to Step 5.

[0284] If the ZVS operation and constraint conditions are not met, it is necessary to continue searching for an available phase shift angle. Under the same operating conditions, when the phase shift angle increases, the fundamental current at the device turn-on time will decrease, which is more conducive to achieving ZVS operation.

[0285] On the other hand, when the phase shift angle increases, the current stress in the loop decreases under the same output power, which is conducive to the realization of the constraint conditions.

[0286] Therefore, the phase shift angle is δ opt , ZVS operation and when the constraint conditions are not met, δ g The step value increases, in [δ opt ,π] to find the phase shift angle δ that meets the ZVS operation and constraint conditions. If h1<0, it means that the expected power operation cannot be achieved with the optimal load at this frequency. According to the principle of highest output power priority, similarly, the phase shift angle should be gradually increased until h1≥0 and the ZVS operation and constraint conditions are met.

[0287] If such a phase shift angle exists, the group of parameters is recorded and the calculation of the next frequency point is performed, and the process goes to Step 5; if such a phase shift angle does not exist, the process goes directly to Step 5.

[0288] The embodiment of the present invention realizes energy efficiency control of the wireless power transmission system by adjusting the operating frequency of the inverter and the phase shift angle of the inverter, so that the system transmission efficiency is the highest and the optimization effect is better.

[0289] Specifically, in some embodiments, the energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including:

[0290] By adjusting the input voltage of the inverter, energy efficiency control of the wireless power transmission system can be achieved.

[0291] For example, Figure 8 This is the fourth block diagram of the energy efficiency control of the wireless power transmission system provided by the embodiment of the present invention, such as Figure 8 As shown, the compensation device includes: primary parallel compensation capacitor C r , primary side series compensation capacitor C P , Secondary side series compensation capacitor C S and compensation inductor L r .

[0292] C r The corresponding compensation parameter is k Cr , which represents the ratio of the actual capacitance of the primary parallel compensation capacitor to its ideal value.

[0293] C P The corresponding compensation parameter is k CP , which represents the ratio of the actual capacitance of the primary series compensation capacitor to its ideal value.

[0294] C S The corresponding compensation parameter is k CS , which represents the ratio of the actual capacitance of the secondary side series compensation capacitor to its ideal value.

[0295] L r The corresponding compensation parameter is k Lr , which represents the ratio of the actual value of the primary series compensation inductance to its ideal value.

[0296] The mutual inductance parameter is k M , which represents the ratio of the actual value of mutual inductance to the ideal value.

[0297] The load parameter is k R , which represents the ratio of the actual value of the load resistance to the rated value.

[0298] The system operating frequency is ω, the ideal resonant frequency is ω0, k ω Represents the ratio of the secondary resonant frequency to the ideal resonant frequency, k ω2 It represents the ratio of the actual operating frequency to the secondary resonant frequency.

[0299] When the system is in resonance, the following relationship exists:

[0300]

[0301] Among them, L s Represents the self-inductance of the secondary coil, C S0 Represents the ideal value of the secondary side series compensation capacitor.

[0302] System impedance matching is crucial to improving the transmission efficiency of wireless power transmission systems. In actual systems, changes in output power, changes in mutual inductance caused by the position shift of the primary and secondary sides, and drift of compensation parameters will destroy the impedance matching relationship of the system and may lead to a decrease in transmission efficiency. By adjusting the input voltage, in theory, the equivalent load resistance can be adjusted to the optimal load resistance as much as possible to achieve the purpose of efficiency optimization control.

[0303] This embodiment will analyze the impact of inverter input voltage adjustment on system transmission efficiency based on the changes in output power, mutual inductance and compensation parameters.

[0304] Among the three parts of the inverter, coupling and compensation mechanism and secondary rectifier, although the loss proportion of the inverter and secondary rectifier cannot be ignored, there are fewer factors that affect the efficiency of the converter, only frequency, switching current and on-state current. The factors that affect the working state of the coupling and compensation mechanism include frequency, compensation parameters, mutual inductance and load parameters. The efficiency change of the coupling and compensation mechanism caused by poor impedance matching is more obvious. In addition, the main loss source of the primary inverter is switching loss. Accurate calculation of switching loss requires phase shift angle and switching current information, which will significantly increase the complexity of impedance matching relationship calculation, which is not conducive to engineering implementation. Therefore, considering the efficiency change and the difficulty of implementation, only the coupling and compensation mechanism is considered when deriving the optimal load resistance below.

[0305] When the frequency, coupling and compensation parameters deviate, the current I S The expression is as follows:

[0306]

[0307] Among them, a, b, c, d, and g1 are all intermediate variables, U S0 represents the output voltage of the system when only the mutual inductance changes, k U is the ratio of the actual input voltage to the ideal input voltage, δ represents the preset phase shift angle, which is generally set to π to fully utilize the current carrying capacity of the power conversion device, R E0 The ideal value of the equivalent load resistance at the rectifier input, Q in Represents the load quality factor of the primary inverter, k R It represents the ratio of the actual value of the load resistance to the rated value, and Q0 represents the load quality factor of the secondary side of the coupling mechanism.

[0308] The expressions of a, b, c, d, and g1 are as follows:

[0309]

[0310] When the system operating frequency is the actual operating frequency, the ratio of the system output power to the rated power is k Po for:

[0311]

[0312] When there are deviations in output power, mutual inductance and compensation parameters, the transmission efficiency of the coupling and compensation mechanism is:

[0313]

[0314] Among them, P LP Represents the power loss of the primary side of the coupling mechanism, P LS Represents the power loss on the secondary side of the coupling mechanism, P o Indicates output power, P Lr Indicates compensation for inductor loss, i S Represents the true value of the secondary coil current, i in Represents the true value of the primary inverter output current, i P Represents the true value of the primary coil current, i Cr Represents the true value of the current of the primary parallel compensation capacitor, P C Indicates the compensation capacitor loss.

[0315] g2 and g3 are intermediate variables, and their expressions are as follows:

[0316]

[0317]

[0318] According to the ratio of the output power to the rated power of the wireless power transmission system, that is, according to formula (4-4), the output power is the preset power k Po P O When the load resistance first change coefficient k R , which is expressed as follows:

[0319]

[0320] Among them, the expression of g4 is as follows:

[0321]

[0322] In formula (4-8), let Then when h1 meets the following conditions, the power demand of the load can be met.

[0323]

[0324] Substituting formula (4-8) into formula (4-5) and taking the derivative of the transmission efficiency with respect to the input voltage variation coefficient, we can obtain the input voltage variation coefficient k at the extreme point: U Satisfies the following formula:

[0325]

[0326] After numerical verification, g2, g3 and g4 are all positive numbers. Considering the input voltage variation coefficient k U Only in [k U-min , k U-max ] changes within the interval, where k U-min =U in-min / U in0 , k U-max =U in-max / U in0 (U in-min , U in0 and U in-max Respectively represent the minimum, rated and maximum values ​​of the inverter input voltage), so the input voltage variation coefficient k U When the following formula (4-12) is satisfied, maximum efficiency control can be achieved by adjusting the input voltage.

[0327]

[0328] There is a complex coupling relationship between the coupling and compensation parameter deviation, inverter operating frequency and phase shift angle and system transmission power capacity, inverter device working state and transmission efficiency. Adjusting the input voltage will affect the system power characteristics. When the parameter deviation state is different, the influence law will also change. The arbitrary reduction of the analysis and control dimensions will lead to defects in the comprehensive characteristics of the system. Therefore, when formulating the control strategy, comprehensive consideration should be given from the system perspective to achieve efficient and stable operation within the wide parameter range of the system.

[0329] The transmission power and efficiency characteristics of the system are affected by multiple factors such as load demand, coupling and compensation parameter deviation, and input voltage regulation is an effective means of regulating the above characteristics. At the same time, due to the complex nonlinear coupling relationship between input voltage, coupling and compensation parameters, and system efficiency characteristics, factors such as transmission power capacity and transmission efficiency need to be considered comprehensively when selecting input voltage.

[0330] Therefore, by relying on the real parameters of the coupling and compensation mechanism obtained by online parameter estimation, the optimal efficiency control can be achieved theoretically by adjusting the inverter input voltage. Considering the system tolerance and the voltage and current tolerance of the device, in addition to the constraints shown in formulas (4-10) and (4-12), the voltage and current of the compensation device should also be constrained. The voltage and current of the compensation device meet the third preset condition to ensure that the system can work safely.

[0331] The third precondition is as follows:

[0332]

[0333]

[0334] Among them, I in Indicates the effective value of the inverter output current, I Cr Indicates the compensation capacitor C r The effective value of the current, I P Indicates the compensation capacitor C P The effective value of the current, I S Indicates the compensation capacitor C s The effective value of the current, U Cr Indicates the compensation capacitor C r The effective value of the voltage, U CP Indicates the compensation capacitor C r The effective value of the voltage, U Cs Indicates the compensation capacitor C s The effective value of the voltage.

[0335] The subscript “-up” indicates the safety upper limit of the corresponding indicator.

[0336] Through the above method, the characteristic indicators of each link of the system can be calculated. The purpose of implementing the control strategy is to achieve comprehensive control of multiple objectives such as meeting load power requirements and maximizing efficiency on the basis of satisfying the above constraints.

[0337] When the mutual inductance and compensation parameters are offset, the above two objectives may not be met at the same time. In this state, meeting the load power demand will be given the highest priority. Secondly, the control strategy should maximize efficiency.

[0338] On the other hand, after the system design is completed, the maximum heat dissipation capacity of the device has been determined. A significant decrease in efficiency will mean that the proportion of power lost in the circuit will increase, which may cause thermal failure of the system, reduce the life of the device, and even cause safety accidents. Therefore, it is also necessary to limit the power loss of the system, which is closely related to the specific design of the system.

[0339] In order to maintain the scalability of theoretical analysis, this embodiment limits the lower limit of transmission efficiency, as shown in formula (4-20), that is, when the calculated system efficiency is not less than the lower limit value η low When , the system is considered to be able to operate normally, that is:

[0340] η≥η low (4-20)

[0341] If the coupling and compensation parameters deviate seriously and cannot meet the above control objectives and constraints, the system needs to operate at reduced power. At the same time, the components that need to be replaced are determined based on the estimated parameters to provide a basis for system maintenance.

[0342] In summary, the control objective of the WPT system is multi-objective comprehensive optimization control under multiple constraints with the inverter input voltage as the control variable.

[0343] Although the input voltage variation coefficient corresponding to the highest efficiency can be directly calculated according to formula (4-11), it is difficult to directly use intelligent algorithms to find the best solution due to the limited computing power of the controller in the actual system and the existence of many constraints. Here, the input voltage is discretized and the optimal input voltage is searched by traversal optimization. The step values ​​of the input voltage are set to k U-g , the search range is set to [k U-min , k U-max ].

[0344] Fig. 9 FIG. 4 is a fourth schematic diagram of energy efficiency control logic of a wireless power transmission system provided by an embodiment of the present invention. Fig. 9 As shown in the figure, the specific process of traversal optimization is divided into the following steps:

[0345] Step 1: Initialize parameters and perform online parameter estimation.

[0346] Step 2: Change the input voltage coefficient k U Initialized to k U-max .

[0347] Step 3: Determine whether the current input voltage can meet the system power requirement. Calculate h1 according to formula (4-10), and decide whether to proceed to Step 4 based on the positive or negative value of h1.

[0348] If h1 is a non-negative number, it means that the system can output the expected power k under the current input voltage. Po P O , go to Step 4 to continue calculation.

[0349] If h1 is negative, it means that the system cannot meet the load k under the current parameters. Po P OThe power demand is determined, and the process goes to Step 5;

[0350] Step 4: Determine whether there is an optimal input voltage change coefficient under the current parameters. According to formula (4-12), h2, g1, g2 and g3 are all non-negative numbers, so it is only necessary to determine whether h2 is within [k U-min , k U-max ] range.

[0351] If h2 is in [k U-min , k U-max ] range, it means that it is possible to achieve optimal load regulation under this parameter, and the calculation is continued in Step 6.

[0352] If h2 is not in [k U-min , k U-max ] range, it means that although the system can achieve the expected power output, it cannot be adjusted to the optimal load. At this time, the goal of traversal optimization becomes to find the most efficient parameter combination that meets the constraints, and then go to Step 7;

[0353] Step 5: It indicates that the system cannot meet the load k under the current parameters. Po P O The power demand indicates that the current system cannot guarantee the safe and stable output of the expected power because the coupling and compensation parameters deviate too much from the rated state. At this time, the expected output power should be reduced. Let the output power change ratio be k Po -k Po-g , and continue the calculation in Step 2 until a parameter combination that meets the design objectives and constraints is found. After the system stops working, the coupling and compensation parameters should be adjusted according to the results of the online parameter estimation to restore the system to the rated state.

[0354] Step 6: Find the optimal available input voltage variation coefficient. Calculate the optimal input voltage variation coefficient k under the current parameters according to formula (4-11) U-opt , let the phase shift angle be k U =k U-opt , and substitute it into formula (4-10) to calculate h1.

[0355] If h1≥0, it means that under this parameter, the system can achieve the expected power and optimal load operation at the same time. At this time, the constraint conditions are calculated and judged.

[0356] If the constraints are met, it means that the two control objectives and all constraints can be met at the same time under this parameter. Record this set of parameters and adjust the input voltage change coefficient to k. U-opt ;

[0357] If the constraint condition is not met, it is necessary to continue searching for the available input voltage variation coefficient. Under the same operating conditions, when the input voltage variation coefficient increases, the current stress in the loop decreases under the same output power, which is conducive to the realization of the constraint condition.

[0358] Therefore, the input voltage variation coefficient is k U-opt , when the constraints are not met, k U-g The step value increases in [k U-opt , k U-max ] to find the input voltage variation coefficient k that meets the constraint conditions U-opt .

[0359] If h1<0, it means that the expected power operation cannot be achieved with the optimal load under the current parameters. According to the principle of highest priority for output power, similarly, the input voltage variation coefficient should be gradually increased until h1≥0 and the constraint condition is met.

[0360] If such an input voltage variation coefficient exists, record this set of parameters and proceed to Step 8.

[0361] Step 7: Find the available input voltage variation coefficient. When other parameters are fixed, when the input voltage variation coefficient is less than the optimal input voltage variation coefficient, the transmission efficiency of the coupling and compensation mechanism increases with the increase of the input voltage variation coefficient, and when the input voltage variation coefficient is greater than the optimal input voltage variation coefficient, the transmission efficiency decreases monotonically with the input voltage variation coefficient.

[0362] Therefore, when the difference between the input voltage variation coefficient and the optimal input voltage variation coefficient is the smallest, the system efficiency can reach the maximum value under the current parameters. Therefore, let the initial value of the input voltage variation coefficient be k U-max , the decreasing step value is k U-g , in [k U-min , k U-max ] range to search for an input voltage variation coefficient that meets the output power requirement, i.e., h1 ≥ 0 and satisfies the constraints.

[0363] If such an input voltage variation coefficient exists, it means that although this set of parameters does not achieve the optimal efficiency of the system, it can output the expected power and meet all constraints. Therefore, this set of parameters is recorded as a candidate and transferred to Step 8;

[0364] If there is no input voltage variation coefficient that meets the conditions, it means that all control objectives cannot be achieved under the parameters while satisfying the constraints, and the process goes to Step 8.

[0365] Step 8: Check the data record table to see if there is any parameter combination that meets the design objectives and constraints.

[0366] If so, select the most efficient set of implementations;

[0367] If it does not exist, it means that the current system cannot guarantee the safe and stable output of the expected power because the coupling and compensation parameters deviate too much from the rated state, and then go to Step 5 to continue the calculation.

[0368] The embodiment of the present invention realizes energy efficiency control of the wireless power transmission system by adjusting the input voltage of the inverter, so that the system transmission efficiency is the highest and the optimization effect is better.

[0369] Specifically, in some embodiments, the energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including:

[0370] By adjusting the operating frequency of the inverter and the input voltage of the inverter, energy efficiency control of the wireless power transmission system can be achieved.

[0371] For example, Fig.10 This is the fifth block diagram of energy efficiency control of the wireless power transmission system provided by the embodiment of the present invention, such as Fig.10 As shown, the compensation device includes: primary parallel compensation capacitor C r , primary side series compensation capacitor C P , Secondary side series compensation capacitor C S and compensation inductor L r .

[0372] C r The corresponding compensation parameter is k Cr , which represents the ratio of the actual capacitance of the primary parallel compensation capacitor to its ideal value.

[0373] C P The corresponding compensation parameter is k CP , which represents the ratio of the actual capacitance of the primary series compensation capacitor to its ideal value.

[0374] C S The corresponding compensation parameter is k CS , which represents the ratio of the actual capacitance of the secondary side series compensation capacitor to its ideal value.

[0375] L r The corresponding compensation parameter is k Lr , which represents the ratio of the actual value of the primary series compensation inductance to its ideal value.

[0376] The mutual inductance parameter is k M , which represents the ratio of the actual value of mutual inductance to the ideal value.

[0377] The load parameter is k R , which represents the ratio of the actual value of the load resistance to the rated value.

[0378] The system operating frequency is ω, the ideal resonant frequency is ω0, k ω Represents the ratio of the secondary resonant frequency to the ideal resonant frequency, k ω2 It represents the ratio of the actual operating frequency to the secondary resonant frequency.

[0379] When the system is in resonance, the following relationship exists:

[0380]

[0381] Among them, L s Represents the self-inductance of the secondary coil, C S0 Represents the ideal value of the secondary side series compensation capacitor.

[0382] System impedance matching is crucial to improving the transmission efficiency of wireless power transmission systems. In actual systems, changes in output power, changes in mutual inductance caused by the position shift of the primary and secondary sides, and drift of compensation parameters will destroy the impedance matching relationship of the system and may lead to a decrease in transmission efficiency. By adjusting the inverter operating frequency and input voltage, the equivalent load resistance can theoretically be adjusted to the optimal load resistance as much as possible to achieve the purpose of efficiency optimization control.

[0383] This embodiment will analyze the impact of inverter operating frequency and input voltage adjustment on system transmission efficiency based on the changes in output power, mutual inductance and compensation parameters.

[0384] Among the three parts of the inverter, coupling and compensation mechanism and secondary rectifier, although the loss proportion of the inverter and secondary rectifier cannot be ignored, there are fewer factors that affect the efficiency of the converter, only frequency, switching current and on-state current. The factors that affect the working state of the coupling and compensation mechanism include frequency, compensation parameters, mutual inductance and load parameters. The efficiency change of the coupling and compensation mechanism caused by poor impedance matching is more obvious. In addition, the main loss source of the primary inverter is switching loss. Accurate calculation of switching loss requires phase shift angle and switching current information, which will significantly increase the complexity of impedance matching relationship calculation, which is not conducive to engineering implementation. Therefore, considering the efficiency change and the difficulty of implementation, only the coupling and compensation mechanism is considered when deriving the optimal load resistance below.

[0385] When the frequency, coupling and compensation parameters deviate, the current I S The expression is as follows:

[0386]

[0387] Among them, a, b, c, d, and g1 are all intermediate variables, U S0 represents the output voltage of the system when only the mutual inductance changes, k Uis the ratio of the actual input voltage to the ideal input voltage, δ represents the preset phase shift angle, which is generally set to π to fully utilize the current carrying capacity of the power conversion device, R E0 The ideal value of the equivalent load resistance at the rectifier input, Q in Represents the load quality factor of the primary inverter, k R It represents the ratio of the actual value of the load resistance to the rated value, and Q0 represents the load quality factor of the secondary side of the coupling mechanism.

[0388] The expressions of a, b, c, d, and g1 are as follows:

[0389]

[0390] When the system operating frequency is the actual operating frequency, the ratio of the system output power to the rated power is k Po for:

[0391]

[0392] When there are deviations in output power, mutual inductance and compensation parameters, the transmission efficiency of the coupling and compensation mechanism is:

[0393]

[0394] Among them, P LP Represents the power loss of the primary side of the coupling mechanism, P LS Represents the power loss on the secondary side of the coupling mechanism, P o Indicates output power, P Lr Indicates compensation for inductor loss, i S Represents the true value of the secondary coil current, i in Represents the true value of the primary inverter output current, i P Represents the true value of the primary coil current, i Cr Represents the true value of the current of the primary parallel compensation capacitor, P C Indicates the compensation capacitor loss.

[0395] g2 and g3 are intermediate variables, and their expressions are as follows:

[0396]

[0397] According to the ratio of the output power to the rated power of the wireless power transmission system, that is, according to formula (5-4), the output power is the preset power k Po P O When the load resistance first change coefficient k R , which is expressed as follows:

[0398]

[0399] Among them, the expression of g4 is as follows:

[0400]

[0401] In formula (5-8), let Then when h1 meets the following conditions, the power demand of the load can be met.

[0402]

[0403] Substituting formula (5-8) into formula (5-5) and taking the derivative of the transmission efficiency with respect to the input voltage variation coefficient, we can obtain the input voltage variation coefficient k at the extreme point: U Satisfies the following formula:

[0404]

[0405] After numerical verification, g2, g3 and g4 are all positive numbers. Considering the input voltage variation coefficient k U Only in [k U-min , k U-max ] changes within the interval, where k U-min =U in-min / U in0 , k U-max =U in-max / U in0 (U in-min , U in0 and U in-max Respectively represent the minimum, rated and maximum values ​​of the inverter input voltage), so the input voltage variation coefficient k U When the input voltage and frequency satisfy the following formula (5-12), maximum efficiency control can be achieved by adjusting the input voltage and frequency.

[0406]

[0407] There is a complex coupling relationship between coupling and compensation parameter deviation, inverter operating frequency, input voltage and system transmission power capacity, inverter device working state and transmission efficiency. Adjusting the input voltage and system operating frequency will affect the system power characteristics. The influence law will also change when the parameter deviation state is different. The arbitrary reduction of analysis and control dimensions will lead to defects in the comprehensive characteristics of the system. Therefore, when formulating the control strategy, comprehensive consideration should be given from the system perspective to achieve efficient and stable operation within a wide parameter range of the system.

[0408] The transmission power and efficiency characteristics of the system are affected by many factors such as load demand, coupling and compensation parameter deviation, and input voltage and frequency regulation are effective means to control the above characteristics. At the same time, due to the complex nonlinear coupling relationship between input voltage, system operating frequency, coupling and compensation parameters, and system efficiency characteristics, factors such as transmission power capacity and transmission efficiency need to be considered comprehensively when selecting input voltage and operating frequency.

[0409] Therefore, by relying on the real parameters of the coupling and compensation mechanism obtained by online parameter estimation, the optimal efficiency control under the ZVS condition can be achieved theoretically by adjusting the inverter input voltage and frequency. Considering the system tolerance and the voltage and current tolerance of the device, in addition to the constraints shown in formulas (5-10) and (5-12), the voltage and current of the compensation device should also be constrained. The voltage and current of the compensation device meet the third preset condition to ensure that the system can work safely.

[0410] The third precondition is as follows:

[0411]

[0412] Among them, I in Indicates the effective value of the inverter output current, I Cr Indicates the compensation capacitor C r The effective value of the current, I P Indicates the compensation capacitor C P The effective value of the current, I S Indicates the compensation capacitor C s The effective value of the current, U Cr Indicates the compensation capacitor C r The effective value of the voltage, U CP Indicates the compensation capacitor C r The effective value of the voltage, U Cs Indicates the compensation capacitor C s The effective value of the voltage.

[0413] The subscript “-up” indicates the safety upper limit of the corresponding indicator.

[0414] Through the above method, the characteristic indicators of each link of the system can be calculated. The purpose of implementing the control strategy is to achieve comprehensive control of multiple objectives such as load power demand, ZVS operation of inverter switching devices and efficiency maximization on the basis of meeting the above constraints.

[0415] When the mutual inductance and compensation parameters are offset, the above three goals may not be met at the same time. In this state, the highest priority is given to meeting the load power demand. According to the characteristics of the switching device, when the inverter does not achieve ZVS operation, its transmission efficiency will drop significantly and electromagnetic interference will be generated. Therefore, the second priority of the control strategy is to achieve ZVS operation of the inverter switching device. Finally, the control strategy should maximize efficiency on the basis of meeting the above goals.

[0416] On the other hand, after the system design is completed, the maximum heat dissipation capacity of the device has been determined. A significant decrease in efficiency will mean that the proportion of power lost in the circuit will increase, which may cause thermal failure of the system, reduce the life of the device, and even cause safety accidents. Therefore, it is also necessary to limit the power loss of the system, which is closely related to the specific design of the system.

[0417] In order to maintain the scalability of theoretical analysis, this embodiment limits the lower limit of transmission efficiency, as shown in formula (5-20), that is, when the calculated system efficiency is not less than the lower limit value η low When , the system is considered to be able to operate normally, that is:

[0418] η≥η low (5-20)

[0419] If the coupling and compensation parameters deviate seriously and cannot meet the above control objectives and constraints, the system needs to operate at reduced power. At the same time, the components that need to be replaced are determined based on the estimated parameters to provide a basis for system maintenance.

[0420] In summary, the control objective of the WPT system is multi-objective comprehensive optimization control under multiple constraints with the inverter operating frequency and input voltage as control variables.

[0421] Although the input voltage corresponding to the highest efficiency can be directly calculated according to formula (5-11), it is difficult to directly use intelligent algorithms to find the best solution due to the limited computing power of the controller in the actual system and the existence of many constraints. Here, the frequency and input voltage are discretized and the optimal frequency and input voltage are searched by traversal optimization. The step values ​​of the switching frequency are set to f g , the search range of the operating frequency is set to [f min , f max ]. The step values ​​of the input voltage variation coefficient are set to k U-g , the search range is set to [k U-min , k U-max ].

[0422] Fig.11 FIG. 5 is a fifth schematic diagram of energy efficiency control logic of a wireless power transmission system provided in an embodiment of the present invention. Fig.11As shown in the figure, the specific process of traversal optimization is divided into the following steps:

[0423] Step 1: Initialize parameters and perform online parameter estimation.

[0424] Step 2: Initialize the operating frequency f to the search lower limit, here f min .

[0425] Step 3: Change the input voltage coefficient k U Initialized to k U-max .

[0426] Step 4: Determine whether the current frequency can meet the system power requirements. Calculate h1 according to formula (5-10), and decide whether to proceed to Step 5 based on the positive or negative value of h1.

[0427] If h1 is a negative number, it means that the system cannot meet the load k at the current frequency. Po P O If the power requirement is met, the next operating frequency should be searched, that is, go to Step 5;

[0428] If h1 is a non-negative number, it means that at the current frequency, in [k U-min , k U-max ] between the input voltages that can make the system output the desired power k Po P O , go to Step 6 to continue calculation.

[0429] Step 5: Increase the operating frequency to f+f g , if the increased operating frequency does not exceed the upper limit of the frequency range f max , then go to Step 3 to continue the calculation.

[0430] If the increased operating frequency exceeds the upper frequency limit, it means that the program has searched all optional frequencies. At this time, query the data record table to see if there is a parameter combination that meets the design objectives and constraints.

[0431] If so, select the most efficient implementation that meets the ZVS condition; if so, but none of them meets the ZVS condition, select the candidate with the smaller absolute value of current at the time of opening (for example, the absolute value of current at the time of opening is less than the preset value I op-limit The most efficient ones are selected to be implemented to minimize the impact of the opening time and maintain high efficiency.

[0432] If it does not exist, it means that the current system cannot guarantee the safe and stable output of the expected power due to the excessive deviation of the coupling and compensation parameters from the rated state. At this time, the expected output power should be reduced. Let the output power change ratio be kPo -k Po-g , and continue the calculation in Step 2 until a parameter combination that meets the design objectives and constraints is found. After the system stops working, the coupling and compensation parameters should be adjusted according to the results of the online parameter estimation to restore the system to the rated state.

[0433] Step 6: Determine whether there is an optimal input voltage at the current frequency. Calculate h2 according to formula (5-12). According to the parameter deviation range assumed in the previous text, g1, g2 and g3 are all non-negative numbers, so it is only necessary to determine whether h2 is within [k U-min , k U-max ] range.

[0434] If h2 is in [k U-min , k U-max ] range, it means that although the expected power output can be achieved at this frequency, it cannot be adjusted to the optimal load. At this time, the goal of traversal optimization becomes to find the most efficient parameter combination that meets ZVS and constraint conditions, and then go to Step 7;

[0435] If h2 is not in [k U-min , k U-max ] range, it means that it is possible to achieve optimal load regulation at this frequency, and the calculation is continued in Step 8.

[0436] Step 7: Find the optimal available input voltage. When other parameters are fixed, when the input voltage is less than the optimal input voltage, the transmission efficiency of the coupling and compensation mechanism increases with the increase of the input voltage, and when the input voltage is greater than the optimal input voltage, the transmission efficiency decreases monotonically with the increase of the input voltage.

[0437] Therefore, when the difference between the input voltage and the optimal input voltage is the smallest, the system efficiency can reach the maximum value at the current frequency. Therefore, let the initial value of the input voltage be k U-max , the decreasing step value is k U-g , in [k U-min , k U-max ] range to search for an input voltage variation coefficient that meets the output power requirement, i.e., h1 ≥ 0 and satisfies the ZVS operation and constraint conditions.

[0438] If such an input voltage variation coefficient exists, it means that although this set of parameters does not achieve the optimal efficiency of the system, it can output the expected power, achieve ZVS operation and meet all constraints. Therefore, this set of parameters is recorded as a candidate and transferred to Step 5 to continue the calculation;

[0439] If there is no input voltage variation coefficient that satisfies the conditions, it means that all control objectives cannot be achieved at this frequency while satisfying the constraints, and the next frequency point should be calculated and the process goes to Step 5.

[0440] Step 8: Find the available input voltage variation coefficient. Calculate the optimal input voltage variation coefficient k at the current frequency according to formula (5-11) U-opt , let the input voltage change be k U =k U-opt , and substitute it into formula (5-10) to calculate h1.

[0441] If h1≥0, it means that at this frequency, the system can achieve both the expected power and the optimal load operation. At this time, the ZVS and constraint conditions are judged.

[0442] If the ZVS operation and constraint conditions are met, it means that the frequency and input voltage can simultaneously meet the three control objectives and all constraint conditions. Record this set of parameters and calculate the next frequency point, that is, go to Step 5.

[0443] If the ZVS operation and constraint conditions are not met, it is necessary to continue searching for the available input voltage change coefficient. When the input voltage increases, the current stress in the loop decreases under the same output power, which is conducive to the realization of the constraint conditions.

[0444] Therefore, the input voltage variation coefficient is k U-opt , ZVS operation and when the constraint conditions are not met, k U-g The step value increases in [k U-opt , k U-max ] range to find the input voltage variation coefficient that meets the ZVS operation and constraint conditions. If h1<0, it means that the expected power operation cannot be achieved with the optimal load at this frequency. According to the principle of highest output power priority, similarly, the input voltage variation coefficient should be gradually increased until h1≥0 and the ZVS operation and constraint conditions are met.

[0445] If such an input voltage variation coefficient exists, record the group of parameters and calculate the next frequency point, and then go to Step 5; if not, go directly to Step 5.

[0446] The embodiment of the present invention realizes energy efficiency control of the wireless power transmission system by adjusting the operating frequency of the inverter and the input voltage of the inverter, so that the system transmission efficiency is the highest and the optimization effect is better.

[0447] The two most critical indicators in the operation of wireless power transmission systems are power and efficiency. The power required by the load should be maintained as much as possible under wide parameter conditions, and the transmission power should be as high as possible. The present invention achieves comprehensive optimization of the system's power characteristics by adjusting the frequency / phase shift angle / input voltage under conditions that take into account changes in compensation parameters, mutual inductance parameters, and load parameters.

[0448] Compared with the existing technology, it can realize the comprehensive regulation of output power, inverter ZVS operation and transmission efficiency, while the existing technology often only focuses on one or two of them. At the same time, once the system is in operation, the primary goal is to transmit the required energy to the load, followed by the highest possible efficiency. Therefore, in order to fit the actual operating conditions, the output power is given the highest priority during comprehensive regulation, followed by inverter ZVS operation, and finally transmission efficiency optimization. Among them, the realization of inverter ZVS operation is on the one hand to improve the working efficiency of the inverter, and on the other hand to reduce the peak at the moment of opening and reduce electromagnetic interference (EMI).

[0449] Furthermore, while considering the changes of mutual inductance parameters and load parameters, the compensation parameter deviation is also considered. However, the prior art often only considers the changes of mutual inductance and / or load parameters, and assumes that the compensation parameter remains unchanged.

[0450] In addition, the control of inverter ZVS and system transmission efficiency is obtained through analytical calculation rather than traditional phase-locked loop, PI control and other strategies. The adjustment speed is faster and avoids overshoot, drop, oscillation and other phenomena caused by closed-loop adjustment strategies during the adjustment process.

[0451] Regarding the analytical expression, the true value of the inverter output current, the current at the time when the inverter device is turned on, and the system transmission efficiency are derived when the frequency, phase shift angle / input voltage, compensation parameters, mutual inductance parameters and load parameters change simultaneously. Therefore, the optimal frequency / phase shift angle / input voltage can be directly obtained through theoretical calculation. Harmonics are taken into account in the analytical expression, and the loss during compensation is included in the efficiency expression. In the prior art, harmonics and efficiency are usually calculated based on ideal working conditions, without considering the changes in frequency, phase shift angle / input voltage, compensation parameters, mutual inductance and load parameters.

[0452] It should be noted that:

[0453] In the above embodiment, the third preset condition is not limited to the voltage and current of the compensation device, and other conditions such as leakage magnetic intensity may be added as needed;

[0454] Although the efficiency expression in the above embodiment only calculates the compensation and coupling links, it can also be extended to the DC input end of the inverter to the DC output end of the rectifier. Because the analytical expression of the current in each link has been obtained, the conduction and switching losses of the inverter and rectifier devices can be calculated.

[0455] In the above embodiment, the load power is regulated by regulating an additional DC / DC, and the circuit form can also be implemented by an active rectifier circuit. The control strategy can be PI, PID, fuzzy control and other strategies.

[0456] The energy efficiency control device for a wireless power transmission system provided by the present invention is described below. The energy efficiency control device for a wireless power transmission system described below and the energy efficiency control method for a wireless power transmission system described above can be referred to each other.

[0457] Fig.12 is a schematic diagram of the structure of the energy efficiency control device of the wireless power transmission system provided by an embodiment of the present invention, such as Fig.12 As shown, the wireless power transmission system energy efficiency control device provided by the embodiment of the present invention includes:

[0458] The control module 1210 is used to achieve energy efficiency control of the wireless power transmission system by adjusting the inverter parameters under the condition that the parameters of the wireless power transmission system change;

[0459] The wireless power transmission system parameters include one or more of the following parameters:

[0460] Compensation parameters;

[0461] Mutual inductance parameters;

[0462] Load parameters;

[0463] The inverter parameters include one or more of the following parameters:

[0464] Operating frequency;

[0465] Phase shift angle;

[0466] Input voltage.

[0467] It should be noted here that the wireless power transmission system energy efficiency control device provided in the embodiment of the present invention can implement all the method steps implemented in the above-mentioned wireless power transmission system energy efficiency control method embodiment, and can achieve the same technical effect. The parts and beneficial effects that are the same as those in the method embodiment will not be described in detail here.

[0468] Fig.13 An example of a physical structure diagram of an electronic device is shown in FIG. Fig.13 As shown, the electronic device may include: a processor (Processor) 1310, a communication interface (Communications Interface) 1320, a memory (Memory) 1330 and a communication bus 1340, wherein the processor 1310, the communication interface 1320, and the memory 1330 communicate with each other through the communication bus 1340. The processor 1310 may call the logic instructions in the memory 1330 to execute the wireless power transmission system energy efficiency control method, the method comprising:

[0469] Under the condition that the parameters of the wireless power transmission system change, the energy efficiency of the wireless power transmission system can be controlled by adjusting the inverter parameters;

[0470] The wireless power transmission system parameters include one or more of the following parameters:

[0471] Compensation parameters;

[0472] Mutual inductance parameters;

[0473] Load parameters;

[0474] The inverter parameters include one or more of the following parameters:

[0475] Operating frequency;

[0476] Phase shift angle;

[0477] Input voltage.

[0478] In addition, the logic instructions in the above-mentioned memory 1330 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art or the part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory, ROM), random access memory (Random Access Memory, RAM), disk or optical disk and other media that can store program codes.

[0479] On the other hand, the present invention further provides a computer program product, the computer program product comprising a computer program, the computer program can be stored on a non-transitory computer-readable storage medium, and when the computer program is executed by a processor, the computer can execute the wireless power transmission system energy efficiency control method provided by the above methods, the method comprising:

[0480] Under the condition that the parameters of the wireless power transmission system change, the energy efficiency of the wireless power transmission system can be controlled by adjusting the inverter parameters;

[0481] The wireless power transmission system parameters include one or more of the following parameters:

[0482] Compensation parameters;

[0483] Mutual inductance parameters;

[0484] Load parameters;

[0485] The inverter parameters include one or more of the following parameters:

[0486] Operating frequency;

[0487] Phase shift angle;

[0488] Input voltage.

[0489] In another aspect, the present invention further provides a non-transitory computer-readable storage medium having a computer program stored thereon, which is implemented when the computer program is executed by a processor to execute the wireless power transmission system energy efficiency control method provided by the above methods, the method comprising:

[0490] Under the condition that the parameters of the wireless power transmission system change, the energy efficiency of the wireless power transmission system can be controlled by adjusting the inverter parameters;

[0491] The wireless power transmission system parameters include one or more of the following parameters:

[0492] Compensation parameters;

[0493] Mutual inductance parameters;

[0494] Load parameters;

[0495] The inverter parameters include one or more of the following parameters:

[0496] Operating frequency;

[0497] Phase shift angle;

[0498] Input voltage.

[0499] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0500] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0501] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling energy efficiency of a wireless power transmission system, characterized in that: include: Under the condition that the parameters of the wireless power transmission system change, the energy efficiency of the wireless power transmission system can be controlled by adjusting the inverter parameters; The wireless power transmission system parameters include one or more of the following parameters: Compensation parameters; Mutual inductance parameters; Load parameters; The inverter parameters include one or more of the following parameters: Operating frequency; Phase shift angle; Input voltage; The energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including: By adjusting the working frequency of the inverter, the energy efficiency of the wireless power transmission system can be controlled; The compensation components include: primary parallel compensation capacitor C r , primary side series compensation capacitor C P , Secondary side series compensation capacitor C S and compensation inductor L r ; C r The corresponding compensation parameter is k Cr , which represents the ratio of the actual capacitance of the primary parallel compensation capacitor to the ideal value; C P The corresponding compensation parameter is k CP , which represents the ratio of the actual capacitance of the primary series compensation capacitor to the ideal value; C S The corresponding compensation parameter is k CS , which represents the ratio of the actual capacitance of the secondary-side series compensation capacitor to the ideal value; L r The corresponding compensation parameter is k Lr , which represents the ratio of the actual value of the primary series compensation inductance to the ideal value; The mutual inductance parameter is k M , which represents the ratio of the actual value of mutual inductance to the ideal value; The load parameter is k R , which represents the ratio of the actual value of the load resistance to the rated value; The system operating frequency is ω, the ideal resonant frequency is ω0, k ω Represents the ratio of the secondary resonant frequency to the ideal resonant frequency, k ω2 Indicates the ratio of the actual operating frequency to the secondary resonant frequency; When the system is in resonance, the following relationship exists: Among them, L s Represents the self-inductance of the secondary coil, C S0 Represents the ideal value of the secondary side series compensation capacitor; By adjusting the frequency, the equivalent load resistance is adjusted to the optimal load resistance to achieve the purpose of efficiency optimization control; When the frequency conversion and coupling and compensation parameters deviate, the current I S The expression is as follows: Among them, a, b, c, d, and g1 are all intermediate variables, U S0 represents the output voltage of the system when only the mutual inductance changes, δ represents the preset phase shift angle, R E0 The ideal value of the equivalent load resistance at the rectifier input, Q in Represents the load quality factor of the primary inverter, k R It represents the ratio of the actual value of the load resistance to the rated value, Q0 represents the load quality factor of the secondary side of the coupling mechanism; The expressions of a, b, c, d, and g1 are as follows: When the system operating frequency is the actual operating frequency, the ratio of the system output power to the rated power is k Po for: When there are deviations in output power, mutual inductance and compensation parameters, the transmission efficiency of the coupling and compensation mechanism is: Among them, P LP Represents the power loss of the primary side of the coupling mechanism, P LS Represents the power loss on the secondary side of the coupling mechanism, P o Indicates output power, P Lr Indicates compensation for inductor loss, i S Represents the true value of the secondary coil current, i in Represents the true value of the primary inverter output current, i P Represents the true value of the primary coil current, i Cr Represents the true value of the current of the primary parallel compensation capacitor, P C Indicates compensation capacitor loss; g2 and g3 are intermediate variables, and their expressions are as follows: According to the ratio of the output power to the rated power of the wireless power transmission system, the output power is the preset power k Po P O When the load resistance first change coefficient k R , which is expressed as follows: Among them, the expression of g4 is as follows: make Then when h1 meets the following conditions, the power demand of the load can be met: At this time, the transmission efficiency becomes a univariate function only related to frequency; when the compensation parameters are determined, k ω That is to say, the efficiency η is only related to the frequency change coefficient k. ω2 Related; Relying on the real parameters of the coupling and compensation mechanism obtained by online parameter estimation, the optimal efficiency control under ZVS conditions can be achieved by adjusting the frequency; The voltage and current of the compensation device meet the third preset condition to ensure that the system can work safely; The third preset condition is as follows: Among them, I in Indicates the effective value of the inverter output current, I Cr Indicates the compensation capacitor C r The effective value of the current, I P Indicates the compensation capacitor C P The effective value of the current, I S Indicates the compensation capacitor C s The effective value of the current, U Cr Indicates the compensation capacitor C r The effective value of the voltage, U CP Indicates the compensation capacitor C r The effective value of the voltage, U Cs Indicates the compensation capacitor C s The effective value of the voltage; Among them, the subscript "-up" indicates the safety upper limit of the corresponding indicator; The purpose of implementing the control strategy is to achieve comprehensive control that meets multiple objectives on the basis of satisfying the third preset condition; the multiple objectives include load power demand, ZVS operation of inverter switching devices and efficiency maximization; In the case where the mutual inductance and compensation parameters are offset and the multiple objectives cannot be met at the same time, the highest priority of the control strategy is to meet the load power demand; the second priority of the control strategy is to achieve ZVS operation of the inverter switching device; the control strategy achieves efficiency maximization on the basis of meeting the load power demand and achieving ZVS operation of the inverter switching device; In order to limit the power loss of the system, when the calculated system efficiency is not less than the lower limit value η low When , the system is considered to be able to operate normally, that is: η≥η low If the coupling and compensation parameters are seriously deviated and cannot meet the multiple objectives and the third preset condition, the system needs to reduce power operation, and at the same time, the components that need to be replaced are determined based on the estimated parameters to provide a criterion for system maintenance; The control objective of the WPT system is to use the inverter switching frequency as the control variable and multi-objective comprehensive optimization control under multiple constraints; Discretize the switching frequency and search for the switching frequency by traversal optimization; The step values ​​of the switching frequency are set to f g , the search range of the operating frequency is set to [f min , f max ]; The specific process of traversal optimization includes the following steps: Step 1: Parameter initialization and online parameter estimation; Step 2: Initialize the operating frequency f to the search lower limit value f min ; Step 3: Determine whether the current frequency can meet the system power requirement; determine whether to proceed to Step 4 based on the positive or negative value of h1; If h1 is a non-negative number, it means that the system can output the expected power k at the current frequency. Po P O , go to Step 4 to continue calculation; If h1 is a negative number, it means that the system cannot meet the load k at the current frequency. Po P O If the power requirement is met, the next operating frequency is searched, that is, the process goes to Step 5; Step 4: Calculate the current and all constraints at the inverter turn-on time under the current frequency and record them; Step 5: Increase the operating frequency to f+f g , if the increased operating frequency does not exceed the upper limit of the frequency range f max , then go to Step 3 to continue the calculation; If the increased operating frequency exceeds the upper frequency limit, it means that the program has searched all optional frequencies. At this time, check whether there is a parameter combination that meets the design objectives and constraints in the data record table; If there is, then select the most efficient set of implementations that meet the ZVS condition; If they exist, but none of them meet the ZVS condition, then the group with the highest efficiency is selected from the candidates with the smaller absolute value of current at the turn-on time to reduce the impact at the turn-on time and maintain a high efficiency; If it does not exist, let the output power change ratio be k Po -k Po-g , go to Step 2 to continue the calculation until a parameter combination that meets the design objectives and constraints is found; After the system stops working, the coupling and compensation parameters are adjusted according to the results of online parameter estimation to restore the system to the rated state.

2. A wireless power transmission system energy efficiency control device, characterized in that: include: A control module, used to achieve energy efficiency control of the wireless power transmission system by adjusting inverter parameters under the condition that the parameters of the wireless power transmission system change; The wireless power transmission system parameters include one or more of the following parameters: Compensation parameters; Mutual inductance parameters; Load parameters; The inverter parameters include one or more of the following parameters: Operating frequency; Phase shift angle; Input voltage; The energy efficiency control of the wireless power transmission system is achieved by adjusting the inverter parameters, including: By adjusting the working frequency of the inverter, the energy efficiency of the wireless power transmission system can be controlled; The compensation components include: primary parallel compensation capacitor C r , primary side series compensation capacitor C P , Secondary side series compensation capacitor C S and compensation inductor L r ; C r The corresponding compensation parameter is k Cr , which represents the ratio of the actual capacitance of the primary parallel compensation capacitor to the ideal value; C P The corresponding compensation parameter is k CP , which represents the ratio of the actual capacitance of the primary series compensation capacitor to the ideal value; C S The corresponding compensation parameter is k CS , which represents the ratio of the actual capacitance of the secondary-side series compensation capacitor to the ideal value; L r The corresponding compensation parameter is k Lr , which represents the ratio of the actual value of the primary series compensation inductance to the ideal value; The mutual inductance parameter is k M , which represents the ratio of the actual value of mutual inductance to the ideal value; The load parameter is k R , which represents the ratio of the actual value of the load resistance to the rated value; The system operating frequency is ω, the ideal resonant frequency is ω0, k ω Represents the ratio of the secondary resonant frequency to the ideal resonant frequency, k ω2 Indicates the ratio of the actual operating frequency to the secondary resonant frequency; When the system is in resonance, the following relationship exists: Among them, L s Represents the self-inductance of the secondary coil, C S0 Represents the ideal value of the secondary side series compensation capacitor; By adjusting the frequency, the equivalent load resistance is adjusted to the optimal load resistance to achieve the purpose of efficiency optimization control; When the frequency conversion and coupling and compensation parameters deviate, the current I S The expression is as follows: Among them, a, b, c, d, and g1 are all intermediate variables, U S0 represents the output voltage of the system when only the mutual inductance changes, δ represents the preset phase shift angle, R E0 The ideal value of the equivalent load resistance at the rectifier input, Q in Represents the load quality factor of the primary inverter, k R It represents the ratio of the actual value of the load resistance to the rated value, Q0 represents the load quality factor of the secondary side of the coupling mechanism; The expressions of a, b, c, d, and g1 are as follows: When the system operating frequency is the actual operating frequency, the ratio of the system output power to the rated power is k Po for: When there are deviations in output power, mutual inductance and compensation parameters, the transmission efficiency of the coupling and compensation mechanism is: Among them, P LP Represents the power loss of the primary side of the coupling mechanism, P LS Represents the power loss on the secondary side of the coupling mechanism, P o Indicates output power, P Lr Indicates compensation for inductor loss, i S Represents the true value of the secondary coil current, i in Represents the true value of the primary inverter output current, i P Represents the true value of the primary coil current, i Cr Represents the true value of the current of the primary parallel compensation capacitor, P C Indicates compensation capacitor loss; g2 and g3 are intermediate variables, and their expressions are as follows: According to the ratio of the output power to the rated power of the wireless power transmission system, the output power is the preset power k Po P O When the load resistance first change coefficient k R , which is expressed as follows: Among them, the expression of g4 is as follows: make Then when h1 meets the following conditions, the power demand of the load can be met: At this time, the transmission efficiency becomes a univariate function only related to frequency; when the compensation parameters are determined, k ω That is to say, the efficiency η is only related to the frequency change coefficient k. ω2 Related; Relying on the real parameters of the coupling and compensation mechanism obtained by online parameter estimation, the optimal efficiency control under ZVS conditions can be achieved by adjusting the frequency; The voltage and current of the compensation device meet the third preset condition to ensure that the system can work safely; The third preset condition is as follows: Among them, I in Indicates the effective value of the inverter output current, I Cr Indicates the compensation capacitor C r The effective value of the current, I P Indicates the compensation capacitor C P The effective value of the current, I S Indicates the compensation capacitor C s The effective value of the current, U Cr Indicates the compensation capacitor C r The effective value of the voltage, U CP Indicates the compensation capacitor C r The effective value of the voltage, U Cs Indicates the compensation capacitor C s The effective value of the voltage; Among them, the subscript "-up" indicates the safety upper limit of the corresponding indicator; The purpose of implementing the control strategy is to achieve comprehensive control that meets multiple objectives on the basis of satisfying the third preset condition; the multiple objectives include load power demand, ZVS operation of inverter switching devices and efficiency maximization; In the case where the mutual inductance and compensation parameters are offset and the multiple objectives cannot be met at the same time, the highest priority of the control strategy is to meet the load power demand; the second priority of the control strategy is to achieve ZVS operation of the inverter switching device; the control strategy achieves efficiency maximization on the basis of meeting the load power demand and achieving ZVS operation of the inverter switching device; In order to limit the power loss of the system, when the calculated system efficiency is not less than the lower limit value η low When , the system is considered to be able to operate normally, that is: η≥η low If the coupling and compensation parameters are seriously deviated and cannot meet the multiple objectives and the third preset condition, the system needs to reduce power operation, and at the same time, the components that need to be replaced are determined based on the estimated parameters to provide a criterion for system maintenance; The control objective of the WPT system is to use the inverter switching frequency as the control variable and multi-objective comprehensive optimization control under multiple constraints; Discretize the switching frequency and search for the switching frequency by traversal optimization; The step values ​​of the switching frequency are set to f g , the search range of the operating frequency is set to [f min , f max ]; The specific process of traversal optimization includes the following steps: Step 1: Parameter initialization and online parameter estimation; Step 2: Initialize the operating frequency f to the search lower limit value f min ; Step 3: Determine whether the current frequency can meet the system power requirement; determine whether to proceed to Step 4 based on the positive or negative value of h1; If h1 is a non-negative number, it means that the system can output the expected power k at the current frequency. Po P O , go to Step 4 to continue calculation; If h1 is a negative number, it means that the system cannot meet the load k at the current frequency. Po P O If the power requirement is met, the next operating frequency is searched, that is, the process goes to Step 5; Step 4: Calculate the current and all constraints at the inverter turn-on time under the current frequency and record them; Step 5: Increase the operating frequency to f+f g , if the increased operating frequency does not exceed the upper limit of the frequency range f max , then go to Step 3 to continue the calculation; If the increased operating frequency exceeds the upper frequency limit, it means that the program has searched all optional frequencies. At this time, check whether there is a parameter combination that meets the design objectives and constraints in the data record table; If there is, then select the most efficient set of implementations that meet the ZVS condition; If they exist, but none of them meet the ZVS condition, then the group with the highest efficiency is selected from the candidates with the smaller absolute value of current at the turn-on time to reduce the impact at the turn-on time and maintain a high efficiency; If it does not exist, let the output power change ratio be k Po -k Po-g , go to Step 2 to continue the calculation until a parameter combination that meets the design objectives and constraints is found; After the system stops working, the coupling and compensation parameters are adjusted according to the results of online parameter estimation to restore the system to the rated state.

3. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the program, the energy efficiency control method of the wireless power transmission system as claimed in claim 1 is implemented.

4. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the energy efficiency control method of the wireless power transmission system as claimed in claim 1 is implemented.

5. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the energy efficiency control method of the wireless power transmission system as claimed in claim 1 is implemented.

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