Multi-objective global parameter optimization method and wireless power transmission system

Abstract

The present invention provides a multi-objective global parameter optimization method and a wireless power transmission system. When the method is applied to the wireless power transmission system, the mutual inductance value or the resonant frequency between coils is used as the optimization parameter, and the transmission efficiency, the power transmission coefficient, and the capacitor voltage stress coefficient are used as the objective function. The method is to optimize the resonant frequency and the mutual inductance value between coils, and use the linear weighted sum method of multi-objective global optimization to perform optimization design, so as to achieve global optimization of the objective function within the feasible domain.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transmission, and in particular to a multi-objective global parameter optimization method and a wireless power transmission system. Background Art

[0002] Wireless power transmission technology solves the problem of wireless power supply for mobile devices and is gaining more and more attention in the fields of biomedicine, handheld electronic devices, electric vehicles, etc. In the design of actual wireless power transmission systems, the objective functions such as the output power, transmission efficiency, and voltage stress on the compensation capacitor of the wireless power transmission system will change with the change of the resonant frequency. Therefore, it is necessary to adopt a multi-objective global optimization parameter design method to analyze the energy transmission characteristics and capacitor voltage stress characteristics of the wireless power transmission system in detail. By establishing a mathematical model of the wireless power transmission system, a multi-objective global optimization scheme is adopted on the basis of the established mathematical model to achieve the global optimization of the objective function.

[0003] At present, the patent CN 109256840A "A SS compensation type constant current wireless charging power supply and charging method with Buck control at the transmitting end" analyzes the key components of the serial wireless power transmission system with Buck control at the transmitting end, and explains that the system has strong anti-interference and is suitable for use in complex electromagnetic environments, but does not mention the key evaluation indicators of the system such as system efficiency, output power, and capacitor voltage stress. The paper "Analysis and Optimization of Mutual Inductance Coupling Parameters of Inductively Coupled Power Transmission System" (DOI: 10.13334 / j.0258-8013.pcsee.2010.33.007) uses a new performance product method to optimize the mutual inductance coupling parameters. On the basis of meeting the output power, the performance product method optimizes the evaluation indicators such as system efficiency and output power, but the optimization target of this method does not consider the capacitor voltage stress, and because the various objective functions that constitute the performance product have different rates of change and nonlinearity, the objective function may not be optimal within the feasible domain. The paper "Ren Lei, Bo Cuimei, Li Jun, et al. Parameter Optimization of SS-type Wireless Energy Transmission System [J]. Power Electronics Technology, 2016, 50(7): 74-77." takes into account the influence of capacitor voltage stress and uses the method of comprehensive optimization coefficient to optimize the design of the wireless power transmission system. This method has higher transmission efficiency and lower capacitor voltage stress than the performance product optimization. However, due to the different rates of change and nonlinearity of the objective functions, each objective function may not be globally optimal within the feasible domain. Therefore, a linear optimization method that considers system efficiency, output power, capacitor voltage stress and adopts multi-objective global optimization is needed. The linear weighted sum method of the multi-objective global optimization parameter design method of the present invention can meet this requirement. Summary of the invention

[0004] In order to overcome the shortcomings of the comprehensive optimization coefficient in the optimization design of the wireless power transmission system, the present invention takes the mutual inductance and resonant frequency between coils as optimization parameters, and the transmission efficiency, power transmission coefficient, and capacitor voltage stress coefficient as objective functions. The method adopted is to optimize the resonant frequency and the mutual inductance between coils, and use the linear weighted sum method of multi-objective global optimization to perform optimization design, so as to achieve global optimization of the objective function within the feasible domain.

[0005] The present invention provides a multi-objective global parameter optimization method, comprising: setting a dimensionless objective function to normalize data according to a circuit topology relationship of a wireless power transmission system; setting a matching weight for the dimensionless objective function, constructing a multi-objective global optimization evaluation function, converting the dimensionless objective function into an expression related to a resonant frequency; taking the resonant frequency as an independent variable, seeking an optimal solution for the multi-objective global optimization evaluation function, and obtaining an optimization scheme.

[0006] Preferably, the dimensionless objective function includes transmission efficiency, power transmission coefficient, and capacitor voltage stress coefficient;

[0007] The transmission efficiency is the ratio of load active power to input active power;

[0008] The power transmission coefficient is the ratio of the system output power corresponding to other resonant frequency points to the maximum output power when the system output power is maximum at a certain resonant frequency point;

[0009] The capacitor voltage stress coefficient is the ratio of the compensation capacitor voltage stress corresponding to other resonance frequency points to the maximum voltage stress on the compensation capacitor when the voltage stress on the compensation capacitor at a certain resonance frequency point is the maximum.

[0010] In the multi-objective global parameter optimization method provided in this embodiment, by normalizing the output power and capacitor voltage stress into dimensionless power transmission coefficient β and capacitor voltage stress coefficient σ, these two objective functions can be conveniently unified with the transmission efficiency α for multi-objective global optimization design, thus avoiding the disadvantage that the objective functions cannot be globally optimized due to dimensional differences.

[0011] In any of the above embodiments, preferably, the dimensionless objective function is substituted into the constructed multi-objective global optimization evaluation function using the following formula:

[0012] Z=h1(-α)+h2(-β)+h3σ

[0013] Among them, α is the transmission efficiency, β is the power transmission coefficient, and σ is the capacitor voltage stress coefficient; h1, h2, and h3 are the matching weights of the transmission efficiency α, the power transmission coefficient β, and the capacitor voltage stress coefficient σ, respectively.

[0014] Preferably, in any of the above embodiments, after the dimensionless objective function is converted into an expression related to the resonant frequency, the evaluation function of the multi-objective global optimization is expressed by the following formula:

[0015]

[0016] Where w0 is the resonant angular frequency of the transmitting side and the receiving side, M is the mutual inductance of the transmitting coil and the receiving coil, R p , R s They are the transmitting end and the receiving end inductance L p , L s The parasitic resistance of the load is R.

[0017] In any of the above embodiments, the matching weights are preferably set according to the following method: the transmission efficiency, power transmission coefficient, and capacitor voltage stress coefficient are sorted according to their importance in the dimensionless objective function; the dimensionless objective function is matched with weights from large to small according to the sorting order, and the sum of all weights is 1.

[0018] In the multi-objective global parameter optimization method provided in this embodiment, the multi-objective global optimization parameter design gives a larger weight coefficient to the important objective function, while avoiding the error caused by the different rates of change of the objective function in the traditional comprehensive optimization coefficient optimization method, and constructing an evaluation function can transform the optimization problem of the multi-objective vector into a scalar problem of the linear weighted summation of all objectives. It can not only provide guidance for the design and application of practical wireless power transmission systems, but also open up a new path for the research of wireless power transmission systems.

[0019] Preferably, in any of the above embodiments, when obtaining the optimal solution, it includes drawing a relationship curve between the linear weighted sum function Z and the resonant frequency, and calculating the optimal solution of the linear weighted sum function Z at the peak of the curve.

[0020] The present invention also provides a wireless power transmission system, which uses the optimization scheme obtained by the above-mentioned optimization method to perform optimization settings; it includes a high-frequency AC power supply, a transmitting side coil, a transmitting side compensation capacitor, a receiving side compensation capacitor, a receiving side coil, and a load; the high-frequency AC power supply is connected to the transmitting side coil and the transmitting side compensation capacitor, the receiving side compensation capacitor is connected to the receiving side coil and the load, and the transmitting side and the receiving side transmit electric energy through inductive coupling.

[0021] Preferably, the transmitting side coil resonates with the transmitting side compensation capacitor, the receiving side compensation capacitor resonates with the receiving side coil, and when the resonance frequency is equal to the frequency of the high-frequency AC power supply, electric energy is transmitted through inductive coupling.

[0022] In any of the above embodiments, preferably, power transmission is performed according to an optimization scheme based on the set coil inductance value, inductor internal resistance value, load resistance value, effective value of the AC power supply and mutual inductance value of the sending and receiving ends.

[0023] In any one of the above embodiments, preferably, in the optimization scheme, electric energy transmission is performed according to the resonant angular frequency at the optimal solution of the evaluation function of the multi-objective global optimization.

[0024] The wireless power transmission system provided by the embodiment uses a multi-objective global parameter optimization method. The multi-objective global optimization parameter design gives a larger weight coefficient to the important objective function, while avoiding the error caused by the different rates of change of the objective function in the traditional comprehensive optimization coefficient optimization method, and constructing an evaluation function can transform the optimization problem of the multi-objective vector into a scalar problem of the linear weighted summation of all objectives. After optimization, the output power is increased and the resonant frequency is reduced. The reduction of the resonant frequency can improve the safety and reliability of the wireless power transmission system while reducing the switching loss of the inverter. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 A structural block diagram of a wireless power transmission system provided by an embodiment of the present invention;

[0027] Figure 2 A circuit topology for a wireless power transmission system;

[0028] Figure 3 A curve relationship diagram of a linear weighted sum function and a resonant angular frequency in a multi-objective global parameter optimization method provided in an embodiment of the present invention;

[0029] Figure 4 A flow chart of a multi-objective global parameter optimization method provided in an embodiment of the present invention.

[0030] In the figure: 101, high frequency AC power supply; 102, transmitting side coil; 103, transmitting side compensation capacitor; 104, receiving side compensation capacitor; 105, receiving side coil; 106, load. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0032] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit exemplary embodiments according to the present invention.

[0033] The present invention provides a multi-objective global parameter optimization method, such as Figure 4 Shown, including

[0034] S1. According to the circuit topology of the wireless power transmission system, a dimensionless objective function is set to normalize the data;

[0035] S2, set matching weights for dimensionless objective functions and construct a multi-objective global optimization evaluation function.

[0036] S3, converting the dimensionless objective function into an expression related to the resonant frequency;

[0037] S4. Taking the resonant frequency as the independent variable, the evaluation function of multi-objective global optimization is used to find the optimal solution and obtain the optimization plan.

[0038] Preferably, the dimensionless objective function includes transmission efficiency α, power transmission coefficient β, and capacitor voltage stress coefficient σ; the transmission efficiency α is the ratio of load active power to input active power; the power transmission coefficient β is the ratio of the system output power corresponding to other resonant frequency points to the maximum output power when the output power of the system is maximum at a certain resonant frequency point; the capacitor voltage stress coefficient σ is the ratio of the compensation capacitor voltage stress corresponding to other resonant frequency points to the maximum voltage stress on the compensation capacitor when the voltage stress on the compensation capacitor at a certain resonant frequency point is maximum.

[0039] The principle is that when the transmission efficiency of the wireless power transmission system reaches a maximum value at a certain resonant frequency point (or mutual inductance value), and the load power reaches a maximum value at another resonant frequency point (or mutual inductance value), similarly, the voltage stress on the compensation capacitors on the transmitting side and the receiving side is maximum at a certain resonant frequency point (or mutual inductance value). Then, when the transmission efficiency is very high, the power transmission coefficient at this time is very low, and the capacitor voltage stress coefficient is not necessarily optimal. Based on this, the present invention optimizes the resonant frequency of the transmitting coil and the receiving coil and the mutual inductance value between the coils, and adopts a linear weighted sum method of multi-objective global optimization to perform multi-objective global optimization parameter design on the transmission efficiency, power transmission coefficient, and capacitor voltage stress coefficient of the wireless power transmission system as objective functions, so as to achieve global optimization of each objective function within the feasible domain.

[0040] In the multi-objective global parameter optimization method provided in this embodiment, by normalizing the output power and capacitor voltage stress into dimensionless power transmission coefficient β and capacitor voltage stress coefficient σ, these two objective functions can be conveniently unified with the transmission efficiency α for multi-objective global optimization design, thus avoiding the disadvantage that the objective functions cannot be globally optimized due to dimensional differences.

[0041] In the actual multi-objective global optimization parameter design of wireless power transmission systems, we always want to give larger weight coefficients to those relatively important indicators, while avoiding the errors caused by the different rates of change of the objective function in traditional nonlinear parameter optimization methods. Therefore, the optimization problem of multi-objective vectors can be transformed into a scalar problem of linear weighted summation of all objectives. Based on this, a linear weighted sum function Z(x) is constructed and defined as follows:

[0042]

[0043] Where: Z(x) is the evaluation function of the constructed multi-objective global optimization, h i It is the weighting factor of each objective function that makes up the evaluation function.

[0044] The dimensionless objective function is substituted into the constructed multi-objective global optimization evaluation function and is expressed by the following formula:

[0045] Z=h1(-α)+h2(-β)+h3σ

[0046] Among them, α is the transmission efficiency, β is the power transmission coefficient, and σ is the capacitor voltage stress coefficient; h1, h2, and h3 are the matching weights of the transmission efficiency α, the power transmission coefficient β, and the capacitor voltage stress coefficient σ, respectively.

[0047] After converting the dimensionless objective function into an expression related to the resonant frequency, the evaluation function of the multi-objective global optimization is expressed as follows:

[0048]

[0049] Where w0 is the resonant angular frequency of the transmitting side and the receiving side, M is the mutual inductance of the transmitting coil and the receiving coil, R p , R s They are the transmitting end and the receiving end inductance L p , L s The parasitic resistance of the load is R.

[0050] The matching weights are set as follows: the transmission efficiency, power transmission coefficient, and capacitor voltage stress coefficient are ranked according to their importance in the dimensionless objective function;

[0051] According to the ranking, the dimensionless objective function is weighted from large to small, and the sum of all weights is 1. If the project requires that the transmission efficiency α is the most important, the power transmission coefficient β is the second, and the capacitor voltage stress coefficient σ is the third, then h1 can be 0.5, h2 can be 0.3, and h3 can be 0.2, and the sum of h1, h2, and h3 must be 1.

[0052] In the multi-objective global parameter optimization method provided in this embodiment, the multi-objective global optimization parameter design gives a larger weight coefficient to the important objective function, while avoiding the error caused by the different rates of change of the objective function in the traditional comprehensive optimization coefficient optimization method, and constructing an evaluation function can transform the optimization problem of the multi-objective vector into a scalar problem of the linear weighted summation of all objectives. It can not only provide guidance for the design and application of practical wireless power transmission systems, but also open up a new path for the research of wireless power transmission systems.

[0053] When obtaining the optimal solution, it includes drawing a curve of the relationship between the linear weighted sum function Z and the resonant frequency, and calculating the optimal solution of the linear weighted sum function Z at the peak of the curve.

[0054] The present invention also provides a wireless power transmission system, which uses the optimization scheme obtained by the above-mentioned optimization method to perform optimization settings; Figure 1 As shown, it includes a high-frequency AC power supply, a transmitting side coil, a transmitting side compensation capacitor, a receiving side compensation capacitor, a receiving side coil, and a load; the high-frequency AC power supply is connected to the transmitting side coil and the transmitting side compensation capacitor, the receiving side compensation capacitor is connected to the receiving side coil and the load, and the transmitting side and the receiving side transmit electric energy through inductive coupling.

[0055] Preferably, when the transmitting side and the receiving side transmit electric energy through inductive coupling, when the transmitting side coil and the transmitting side compensation capacitor resonate, the receiving side compensation capacitor resonates with the receiving side coil, and the resonance frequency is equal to the frequency of the high-frequency AC power supply.

[0056] In this embodiment, the circuit topology of the wireless power transmission system is as follows: Figure 2 As shown. Among them, U i is a high frequency AC power source 101; Lp is a transmitting coil 102, R p The transmitting coil L p parasitic resistance; Cp is the transmitting side compensation capacitor 103; M is the mutual inductance of the transmitting coil and the receiving coil; Cs is the receiving side compensation capacitor 104; Ls is the receiving side coil 105, R s The receiving coil L s parasitic resistance; R is the load resistance 106; in the optimization scheme, according to the coil inductance value, inductor internal resistance value, load resistance value, effective value of AC power supply, mutual inductance value, and resonant angular frequency of the optimal solution obtained by the system, power transmission is performed according to the obtained resonant angular frequency.

[0057] The given wireless power transmission system parameter values ​​are: the coil inductance value L at the transmitting and receiving ends p =L s =200.6μH, inductor internal resistance R p =R s =1Ω, load resistance R is 10Ω, AC power supply U i The effective value of is 10V, and the mutual inductance value M is 40μH. Select a suitable weighting factor h i (h1,h2,h3) plot the relationship between the linear weighted sum function Z and the resonant angular frequency w0 as shown in Figure 3 As shown, it can be seen that the weighted sum function Z is at the peak of the curve (the resonant angular frequency value at this time is 1.36*10 5 rad / s) to obtain the optimal solution, and finally compare the results of multi-objective global optimization with the results of comprehensive optimization coefficients. The results show that compared with the results obtained by the comprehensive optimization coefficient method, the multi-objective global optimization method can increase the output power by 9.78% and reduce the resonant frequency by 11.77%. The decrease in resonant frequency can reduce the switching loss of the inverter while improving the safety and reliability of the wireless power transmission system. Although the output efficiency of the system is reduced by about 6%, compared with the increase in output power and the decrease in resonant frequency, this sacrifice is worthwhile on the basis of meeting the output power. Therefore, the parameter design method using multi-objective global optimization is satisfactory.

[0058] The wireless power transmission system provided by the embodiment uses a multi-objective global parameter optimization method. The multi-objective global optimization parameter design gives a larger weight coefficient to the important objective function, while avoiding the error caused by the different rates of change of the objective function in the traditional comprehensive optimization coefficient optimization method, and constructing an evaluation function can transform the optimization problem of the multi-objective vector into a scalar problem of the linear weighted summation of all objectives. After optimization, the output power is increased and the resonant frequency is reduced. The reduction of the resonant frequency can improve the safety and reliability of the wireless power transmission system while reducing the switching loss of the inverter.

[0059] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0060] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0061] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0062] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1The steps for the functions specified in one or more boxes.

[0063] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are included in the present invention.

Claims

1. A multi-objective global parameter optimization method, characterized in that: include According to the circuit topology of the wireless power transmission system, a dimensionless objective function is set to normalize the data; Setting matching weights for dimensionless objective functions and constructing a multi-objective global optimization evaluation function; Convert the dimensionless objective function into an expression related to the resonant frequency; Taking the resonant frequency as the independent variable, the optimal solution of the evaluation function of multi-objective global optimization is obtained; Determine the optimization solution; The dimensionless objective function includes transmission efficiency, power transmission coefficient, and capacitor voltage stress coefficient; The transmission efficiency is the ratio of load active power to input active power; The power transmission coefficient is the ratio of the system output power corresponding to other resonant frequency points to the maximum output power when the system output power is maximum at a certain resonant frequency point; The capacitor voltage stress coefficient is the ratio of the compensation capacitor voltage stress corresponding to other resonance frequency points to the maximum voltage stress on the compensation capacitor when the voltage stress on the compensation capacitor at a certain resonance frequency point is the maximum; The dimensionless objective function is substituted into the constructed multi-objective global optimization evaluation function and is expressed by the following formula: Z=h1(-α)+h2(-β)+h3σ; Among them, α is the transmission efficiency; β is the power transmission coefficient; σ is the capacitor voltage stress coefficient; h1, h2, and h3 are the matching weights of the transmission efficiency α, the power transmission coefficient β, and the capacitor voltage stress coefficient σ respectively; After converting the dimensionless objective function into an expression related to the resonant frequency, the evaluation function of the multi-objective global optimization is expressed by the following formula: Where w0 is the resonant angular frequency of the transmitting side and the receiving side; M is the mutual inductance of the transmitting coil and the receiving coil; R p L is the inductance of the transmitter and receiver p The parasitic resistance of s is the receiving inductance L at the receiving end s The parasitic resistance of the load is R.

2. The multi-objective global parameter optimization method according to claim 1, characterized in that: Set the matching weight as follows: The transmission efficiency, power transmission coefficient, and capacitor voltage stress coefficient are ranked according to their importance in the dimensionless objective function; The dimensionless objective function is weighted from large to small according to the ranking order, and the sum of all weights is 1.

3. The multi-objective global parameter optimization method according to claim 1, characterized in that: When obtaining the optimal solution, it includes: drawing a relationship curve between the linear weighted sum function Z and the resonant frequency, and calculating the optimal solution of the linear weighted sum function Z at the peak of the curve.

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