CN113507173B - Coupling parameter identification method and device and wireless power transmission system - Google Patents
Coupling parameter identification method and device and wireless power transmission system Download PDFInfo
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Abstract
One or more embodiments of the present disclosure provide a coupling parameter identification method, an apparatus, and a wireless power transmission system, where in a state where a direct current power supply is turned on and a load is not connected, a first theoretical inversion steady-state output current in the state is determined according to a system model of the wireless power transmission system, a first inversion steady-state output current value is obtained by measurement, and a primary coil self-inductance is determined according to the first theoretical inversion steady-state output current and the first inversion steady-state output current value; and switching on a direct current power supply, switching in a load, determining a second theoretical inversion steady-state output current and a theoretical load voltage in the state according to a system model, measuring a second inversion steady-state output current value and a load voltage value, and determining mutual inductance and secondary coil self-inductance according to the second theoretical inversion steady-state output current, the second inversion steady-state output current value, the theoretical load voltage and the load voltage value. By using the method of the embodiment, the self-inductance of the primary coil, the self-inductance of the secondary coil and the mutual inductance of the primary coil and the secondary coil can be detected and identified.
Description
Technical Field
One or more embodiments of the present disclosure relate to the field of power transmission technologies, and in particular, to a coupling parameter identification method and apparatus, and a wireless power transmission system.
Background
In recent years, the Magnetic Coupling Wireless Power Transfer (MC-WPT) technology has become a research hotspot in the engineering application field due to its safety and convenience. In practical application, in order to increase the coupling parameters of the coupling mechanism, most systems add a magnetic core to the primary and secondary windings. When the relative position between the primary and secondary coils changes, the self inductance and mutual inductance of the coils also change, which causes the system to deviate from a predetermined working state (for example, the system has different detuning or deviation from a soft switch working point), and affects the transmission performance. In some cases, the relative position between the primary and secondary coils is inevitably changed, and in order to ensure the transmission performance, the coupling parameters need to be accurately identified, and compensation is performed or corresponding tuning control is performed based on the coupling parameters, so as to ensure that the system maintains good transmission performance.
Disclosure of Invention
In view of the above, one or more embodiments of the present disclosure are directed to a method, an apparatus and a wireless power transmission system for coupling parameter identification, which are capable of implementing coupling parameter identification.
In view of the above, one or more embodiments of the present disclosure provide a coupling parameter identification method applied to a wireless power transmission system, including:
determining a first theoretical inversion steady-state output current under the conditions of switching on a direct-current power supply and switching off a load, and determining the self-inductance of a primary coil according to the first theoretical inversion steady-state output current and a measured first inversion steady-state output current value;
and determining a second theoretical inversion steady-state output current and a theoretical load voltage under the state of switching on the direct-current power supply and switching on the load, and determining primary and secondary mutual inductance and secondary coil self-inductance according to the second theoretical inversion steady-state output current, a measured second inversion steady-state output current value, the theoretical load voltage and a measured load voltage value.
Optionally, the determining a first theoretical inversion steady-state output current in a state where the dc power supply is switched on and the load is switched off includes:
under the states of switching on a direct-current power supply and switching off a load, determining the falling edge moment of a first period of the output voltage of the high-frequency inverter after a system enters a stable state;
and determining a first theoretical inversion steady-state output current at the falling edge moment according to a system model of the wireless power transmission system.
Optionally, in a case that other circuit parameters of the system model are known, the first theoretical inverting steady-state output current changes with a change in the self-inductance of the primary coil.
Optionally, determining the self-inductance of the primary coil according to the first theoretical inversion steady-state output current and the measured first inversion steady-state output current value includes:
establishing an objective function taking the square of the difference between the first theoretical inversion steady-state output current and the first inversion steady-state output current as the minimum as an optimization target according to the first theoretical inversion steady-state output current and the first inversion steady-state output current value;
and solving the objective function by using a predetermined function solving method to obtain the primary coil self-inductance corresponding to the optimized objective.
Optionally, the determining a second theoretical inversion steady-state output current and a theoretical load voltage in a state where the dc power supply is turned on and the load is turned on includes:
under the state that a direct current power supply is switched on and a load is switched on, determining the falling edge moment of the first period of the output voltage of the high-frequency inverter after the system enters a stable state;
and determining a second theoretical inversion steady-state output current and a theoretical load voltage at the falling edge moment according to a system model of the wireless power transmission system.
Optionally, in a case that other circuit parameters of the system model are known, the second theoretical inversion steady-state output current varies with a variation of a self-inductance of the secondary coil and/or a mutual inductance of the primary and secondary coils, and the theoretical load voltage varies with a variation of the self-inductance of the secondary coil and/or the mutual inductance of the primary and secondary coils.
Optionally, determining the primary-secondary mutual inductance and the secondary-side coil self-inductance according to the second theoretical inversion steady-state output current, the measured second inversion steady-state output current value, the theoretical load voltage, and the measured load voltage value, and includes:
calculating the current square of the difference between the second theoretical inversion steady-state output current and the second inversion steady-state output current value according to the second theoretical inversion steady-state output current and the second inversion steady-state output current value;
calculating the voltage square of the difference between the theoretical load voltage and the load voltage value according to the theoretical load voltage and the load voltage value;
establishing an objective function taking the average value of the square of the current and the square of the voltage to be minimum as an optimization target;
and solving the target function by using a preset function solving method to obtain the primary and secondary side mutual inductance and the secondary side coil self-inductance.
An embodiment of the present specification further provides a coupling parameter identification apparatus, including:
the first coupling parameter identification module is used for determining a first theoretical inversion steady-state output current under the conditions of switching on a direct-current power supply and switching off a load, and determining the self-inductance of the primary coil according to the first theoretical inversion steady-state output current and a measured first inversion steady-state output current value;
and the second coupling parameter identification module is used for determining a second theoretical inversion steady-state output current and a theoretical load voltage under the conditions of switching on the direct-current power supply and switching on the load, and determining primary and secondary mutual inductance and secondary coil self-inductance according to the second theoretical inversion steady-state output current, a measured second inversion steady-state output current value, the theoretical load voltage and a measured load voltage value.
The embodiment of the specification also provides a wireless power transmission system which comprises the coupling parameter identification device.
As can be seen from the above, according to the coupling parameter identification method, the coupling parameter identification device, and the wireless power transmission system provided in one or more embodiments of the present disclosure, in a state where a dc power supply is turned on and a load is not connected, a first theoretical inversion steady-state output current in the state is determined according to a system model of the wireless power transmission system, a first inversion steady-state output current value is obtained by measurement, and a primary coil self-inductance is determined according to the first theoretical inversion steady-state output current and the first inversion steady-state output current value; and then, switching on the direct current power supply, switching in a load, determining a second theoretical inversion steady-state output current and a theoretical load voltage in the state according to a system model, measuring a second inversion steady-state output current value and a load voltage value, and determining mutual inductance and secondary coil self-inductance according to the second theoretical inversion steady-state output current, the second inversion steady-state output current value, the theoretical load voltage and the load voltage value. By using the method of the embodiment, the self-inductance of the primary coil, the self-inductance of the secondary coil and the mutual inductance of the primary coil and the secondary coil can be detected and identified.
Drawings
In order to more clearly illustrate one or more embodiments or prior art solutions of the present specification, the drawings that are needed in the description of the embodiments or prior art will be briefly described below, and it is obvious that the drawings in the following description are only one or more embodiments of the present specification, and that other drawings may be obtained by those skilled in the art without inventive effort from these drawings.
FIG. 1 is a system model diagram of one or more embodiments of the present disclosure;
FIG. 2 is a schematic flow chart of a method according to one or more embodiments of the present disclosure;
FIG. 3 is a schematic diagram of an equivalent circuit for one or more embodiments of the present disclosure;
FIG. 4 is a schematic diagram of an apparatus according to one or more embodiments of the present disclosure;
FIG. 5 is a system diagram illustrating one or more embodiments of the present disclosure.
Detailed Description
For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
It is to be understood that unless otherwise defined, technical or scientific terms used in one or more embodiments of the present disclosure should have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of "first," "second," and similar terms in one or more embodiments of the specification is not intended to indicate any order, quantity, or importance, but rather is used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item listed before the word covers the element or item listed after the word and its equivalents, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", and the like are used merely to indicate relative positional relationships, and when the absolute position of the object being described is changed, the relative positional relationships may also be changed accordingly.
As described in the background section, in a wireless power transmission system, when a system is debugged or a pickup end is in a motion state, a relative position of an original secondary coil changes, and a coupling parameter of a coupling mechanism changes accordingly under the influence of a position change or an environmental change.
In the process of implementing the present disclosure, the applicant finds that a coupling parameter identification method is to identify parameters such as the mutual inductance of the primary and secondary coils and the load by using the self-inductance of the coil as a known quantity, and the method is not suitable for a system in which the coupling parameter changes due to the relative position change or environmental change of the primary and secondary coils; the other coupling parameter identification method is to identify parameters such as coil self-inductance and mutual inductance at the same time, generally obtain parameters such as current, voltage phase, amplitude and the like of the primary coil and the secondary coil through high-frequency sampling, and process the obtained electrical parameters to obtain the coupling parameters.
In view of this, embodiments of the present disclosure provide a coupling parameter identification method and apparatus, and a wireless power transmission system, which have a simple system structure and low cost, and can implement real-time identification of coupling parameters.
Hereinafter, the technical means of the present disclosure will be described in further detail with reference to specific examples.
The coupling parameter identification method provided by the embodiment of the specification is suitable for an LCC-S type magnetic coupling wireless power transmission system, can realize the coupling parameter identification of the LCC-S type MC-WPT system, is particularly suitable for the field debugging of the LCC-S type MC-WPT system, and can realize the real-time detection and identification of the coupling parameter under the condition that the relative position of an original secondary coil changes or the coupling parameter changes due to the influence of environmental factors. The coupling parameters comprise the self-inductance of the primary coil, the self-inductance of the secondary coil and the mutual inductance of the primary coil and the secondary coil.
In some embodiments, a system model of an LCC-S type MC-WPT system is shown in fig. 1, and the system includes a high frequency inverter, a primary side resonant network, a secondary side rectifier, and a boost circuit. The direct current is converted into alternating current through a high-frequency inverter, and the alternating current is input into a primary resonant network to perform voltage or current multiplying action and is transmitted to a primary coil, so that a high-frequency alternating magnetic field is generated in the surrounding space. Under the action of the alternating magnetic field, the secondary coil generates induction voltage, the induction voltage is converted into direct current after passing through the secondary resonant network and being rectified by the secondary rectifier, and the direct current is boosted by the booster circuit and then acts on a load, so that wireless transmission of electric energy is realized.
Specifically, the high-frequency inverter is composed of a switching tube S1-S4The primary side resonance network is composed of a primary side series resonance inductor LfPrimary side parallel harmonicVibration capacitor CfAnd primary side series compensation capacitor CPComposition, DC power supply EdcThe direct current output by the direct current power supply is converted into alternating current through the high-frequency inverter, and the alternating current is transmitted to the primary coil after the voltage or current is multiplied through the primary resonant network. The secondary resonant network is composed of a secondary coil and a secondary resonant compensation capacitor CSThe secondary rectifier is composed of a diode D1-D4The booster circuit is composed of an inductor LbCapacitor Cr、CoSwitching tube S5And a diode D5The secondary side resonant network, the secondary side rectifier and the booster circuit are connected in parallel; under the action of an alternating magnetic field generated by the primary coil, the secondary coil generates an induced voltage, the induced voltage is transmitted to the secondary rectifier through the secondary resonant network, the secondary rectifier rectifies the induced voltage in an alternating current mode, and the output direct current is boosted by the booster circuit and then acts on a load. The current sensor BC1 is connected to the alternating current output end of the high-frequency inverter and used for detecting the output current of the high-frequency inverter, so that overcurrent protection monitoring is facilitated; the voltage sensor BV1 is connected in parallel with the load and is used for detecting the load voltage at two ends of the load, the current sensor BC2 is connected in series with the load and is used for detecting the load current flowing through the load, and the load resistance can be calculated according to the load voltage and the load current.
Based on the system model of the LCC-S type MC-WPT system, the output voltage u of the high-frequency inverter can be obtainedinThe Fourier expansion form of (t) is:
where ω is angular frequency, k is the harmonic order, and t is time.
Under the excitation of the n-th harmonic voltage output by the high-frequency inverter, the obtained F-order inversion output steady-state current is as follows:
If_noutputting the peak value of n-th harmonic of steady-state current for inversionnAnd outputting the n-th harmonic phase difference between the steady-state current and the voltage for inversion. The inverter outputs steady-state current, which is the output current of the high-frequency inverter after the system reaches steady state.
According to kirchhoff's voltage-current law, the following can be obtained:
Zo_nis a primary side parallel resonance capacitor CfThe equivalent impedance of the subsequent stage of (a) is expressed as:
wherein R isPIs an equivalent resistance of the primary coil, LPIs the self-inductance of the primary coil. Zr_nIs the secondary reflection impedance expressed as:
wherein M is the primary and secondary coil mutual inductance. ZS_nIs the secondary circuit impedance expressed as:
wherein L isSFor secondary coil self-inductance, RSIs the equivalent resistance of the secondary coil. Re2The equivalent impedance of the secondary rectifier and its subsequent stage is expressed as:
wherein R ise1To disregard the switching tube S5And the equivalent impedance of the booster circuit and the load in the case of device loss, expressed as:
Re1＝(1-D)2RL (9)
wherein D is a switch tube S5Duty ratio of driving pulse of (2) not to the switching tube S5When a drive pulse is applied, D is 0, RLIs a load resistor.
As shown in fig. 2, based on the wireless power transmission system, one or more embodiments of the present specification provide a coupling parameter identification method, including:
s101: determining a first theoretical inversion steady-state output current under the conditions of switching on a direct-current power supply and switching off a load, and determining the self-inductance of the primary coil according to the first theoretical inversion steady-state output current and the measured first inversion steady-state output current value;
s102: and determining a second theoretical inversion steady-state output current and a theoretical load voltage under the state of switching on the direct-current power supply and switching in the load, and determining mutual inductance and secondary coil self-inductance according to the second theoretical inversion steady-state output current, the measured second inversion steady-state output current value, the theoretical load voltage and the measured load voltage value.
In this embodiment, to identify the self-inductance of the primary coil, the self-inductance of the secondary coil, and the mutual inductance of the primary coil and the secondary coil, a first theoretical inversion steady-state output current in a state where a direct-current power supply is turned on and a load is not connected is determined according to a system model of a wireless power transmission system, a first inversion steady-state output current value is obtained by measurement, and the self-inductance of the primary coil is determined according to the first theoretical inversion steady-state output current and the first inversion steady-state output current value. And then, switching on the direct current power supply, switching in a load, determining a second theoretical inversion steady-state output current and a theoretical load voltage in the state according to a system model, measuring a second inversion steady-state output current value and a load voltage value, and determining mutual inductance and secondary coil self-inductance according to the second theoretical inversion steady-state output current, the second inversion steady-state output current value, the theoretical load voltage and the load voltage value. By using the method of the embodiment, the self-inductance of the primary coil, the self-inductance of the secondary coil and the mutual inductance of the primary coil and the secondary coil can be detected and identified.
Referring to fig. 1, a power supply changeover switch S for switching on or off a dc power supply is provided in a wireless power transmission systemrAnd a load-changeover switch S for switching in or out a loado. When the power supply switch S is closedrTurning off the load switch SoWhen it is time, the DC power supply E is switched ondcCutting out the load; when the power supply change-over switch S is closedrClosing the load changeover switch SoWhen it is time, the DC power supply E is switched ondcAnd switching into the load.
According to the system model shown in the formulas (1) to (9), when the direct-current power supply is switched on and the load is switched off, the load is regarded as infinite, and the secondary-side related equivalent impedance R shown in the formulas (6) to (9)e1、Re2、ZS_n、Zr_nApproaching to 0, the equivalent circuit in the current state can be obtained as shown in fig. 3, and in this state, the coupling parameter to be identified is only the self-inductance of the primary coil.
In some embodiments, determining the first theoretical inverting steady-state output current in a state where the dc power source is switched on and the load is switched off includes:
under the states of switching on a direct-current power supply and switching off a load, after a system enters a stable state, determining the falling edge moment of a first period of the output voltage of the high-frequency inverter;
and determining a first theoretical inversion steady-state output current at the falling edge moment according to a system model.
In this embodiment, in a state where the dc power supply is turned on and the load is switched off, after the system enters a steady state, the falling edge time T of the first cycle of the output voltage of the high-frequency inverter is reached1，T1＝m1T，m1Is a positive integer, and T is the system operation period.
According to a system model, under the conditions of switching on a direct-current power supply and switching off a load, determining a derivation process of a first theoretical inversion steady-state output current as follows:
in the off-load state, the equivalent impedance change shown in formula (5) is:
order to
Equation (10) reduces to:
Zo_n＝RP+jα1_n (11)
substituting equation (12) into equation (4) yields:
order to
Equation (12) reduces to:
Zin_n＝β1_n+jα2_n (13)
the following formula (1), (3) and (13) are obtained:
by substituting the formulae (14) and (15) for the formula (2), T can be obtained in the load-cut state1The first theoretical inverted steady-state output current at time is:
according to equations (10) - (16), in the system model, the inductance L is in series resonance at the primary sidefPrimary side parallel resonance capacitor CfPrimary side series compensation capacitor CPEquivalent resistance R of primary coilPSecondary coil equivalent resistance RSSecondary side resonance compensation capacitor CSAnd a booster circuit inductor LbCapacitor Cr、CoWith known equivalent circuit parameters, without applying to the switching tube S5Under the condition of applying a driving signal, the magnitude of the first theoretical inversion steady-state output current is along with the self-inductance L of the primary coilPMay vary.
In some embodiments, determining the primary coil self-inductance based on the first theoretical inverted steady-state output current and the first inverted steady-state output current value comprises:
establishing an objective function taking the square of the difference between the first theoretical inversion steady-state output current and the second theoretical inversion steady-state output current as the minimum as an optimization target according to the first theoretical inversion steady-state output current and the first inversion steady-state output current value;
and solving the objective function by using a predetermined function solving method to obtain the primary coil self-inductance corresponding to the optimized objective.
In this embodiment, in a state where a load is switched out, in order to identify a self-inductance of a primary coil, an objective function is constructed according to a first theoretical inversion steady-state output current and a first inversion steady-state output current value, where the objective function takes a square of a difference between the two as a minimum as an optimization target, and the objective function is expressed as:
F(LP)＝|if(T1)-if(T1)mea|2 (17)
wherein if(T1)meaIs T1At that time, the output current value of the high-frequency inverter measured by the current sensor. i.e. if(T1) Is T1The first theoretical inverse steady state output current at a time, which is self-induced with the primary coil LPIs changed, and the optimal self-inductance L of the primary coil is found by solving the objective function shown in the formula (17)PAnd if the square of the difference between the first theoretical inversion steady-state output current and the first inversion steady-state output current value is the minimum, the optimal self-inductance of the primary coil is the determined self-inductance of the primary coil, so that the self-inductance of the primary coil is identified.
In some embodiments, a genetic algorithm may be used to solve the objective function shown in equation (17) to obtain the optimal self-inductance of the primary coil. The method for solving the objective function by utilizing the genetic algorithm specifically comprises the following steps:
under the states of switching on a direct current power supply and switching off a load, initializing a system model according to various circuit parameters of a wireless power transmission network and a measured first inversion steady-state output current value, initializing a population by taking the self-inductance of a primary coil as a particle, and initializing parameters of a genetic algorithm, including setting the population scale, the iteration times, the cross probability, the variation probability and the like; calculating the fitness value by taking the formula (17) as a fitness value function for each individual in the population, and reflecting the closeness degree of a theoretical calculation value and an actual measurement value; after calculation, sorting and screening the fitness value corresponding to each individual, setting a generation ditch of each generation, and selecting a parent generation and a parent generation from the individuals, wherein the higher the fitness value is, the higher the possibility of selection is; carrying out cross mutation on the selected parent and the mother generation according to the cross probability and the mutation probability to generate new filial generations; and (3) forming a new generation population by the new filial generation and the individuals survived from the previous generation, and executing the process until the iteration times are reached or the iteration termination condition is met to obtain the optimal individuals in the population, wherein the optimal individuals are the optimal self-inductance of the primary coil. The above is a basic process for solving the optimal solution of the objective function by using the genetic algorithm, and the present embodiment does not explain the detailed principles and processes of the genetic algorithm. It should be noted that, in order to solve the objective function, other algorithms (for example, a particle swarm algorithm, a simulated annealing algorithm, etc.) may also be used to perform calculation and solution, and the specific algorithm is not limited in this embodiment.
In some embodiments, determining the second theoretical inverting steady-state output current and the theoretical load voltage in a state where the dc power source is switched on and the load is switched on includes:
under the state of switching on a direct-current power supply and switching in a load, after a system enters a stable state, determining the falling edge time of a first period of the output voltage of the high-frequency inverter;
and determining a second theoretical inversion steady-state output current and a theoretical load voltage at the falling edge moment according to a system model.
In this embodiment, in a state where the dc power supply is turned on and the load is switched on, after the system enters a steady state, the falling edge time T of the first cycle of the output voltage of the high-frequency inverter is reached2，T2＝m2T，m2Is a positive integer, and T is the system operation period.
According to the system model, under the conditions that a direct-current power supply is switched on and a load is switched on, the derivation process for determining the second theoretical inversion steady-state output current is as follows:
order:
according to the system model, the secondary side circuit impedance shown in equation (7) is expressed as:
ZS_n＝β2_n+jα3_n (19)
the secondary side reflection impedance shown in equation (6) is expressed as:
Zr_n＝β3_n+jα4_n (20)
order:
substituting the formula (21) into the formula (5) to obtain the primary side parallel resonance capacitor CfThe equivalent impedance of the subsequent stage of (2) is:
Zo_n＝β4_n+jα5_n (22)
substituting equation (21) into equation (4) yields the input impedance of the system as:
Zin_n＝β5_n+jα6_n (23)
according to the formulas (1), (3) and (23), the following results are obtained:
substituting the equations (24) and (25) into the equation (2) can obtain T in the cut-in load state2The second theoretical inversion steady-state output current at the moment is:
according to equations (18) to (26), in the system model, the primary side series resonance inductance LfPrimary side parallel resonance capacitor CfPrimary side series compensation capacitor CPEquivalent resistance R of primary coilPSecondary coil equivalent resistance RSSecondary side resonance compensation capacitor CSAnd a booster circuit inductor LbCapacitor Cr、CoLoad resistance RLWith known equivalent circuit parameters, without applying to the switching tube S5Applying a drive signal, self-inductance L of the primary coilPUnder the determined condition, the magnitude of the second theoretical inversion steady-state output current is along with the self-inductance L of the secondary coilSAnd/or the primary and secondary coil mutual inductance M.
For the derivation of the theoretical load voltage, in the case of considering only the output voltage of the high-frequency inverter as the fundamental wave, it can be obtained from equation (3), and the output current vector of the high-frequency inverter can be expressed as:
the effective value of the output voltage of the high-frequency inverter can be expressed as:
the current vector of the primary coil of the system model can be obtained according to kirchhoff voltage and current law
Output current vector of high frequency inverter
Have the following relationship between:
the secondary coil induced voltage can be expressed as:
the input voltage vector of the secondary rectifier is represented as:
further, the input voltage of the booster circuit is obtained as:
the theoretical load voltage is obtained as follows:
according to equations (27) to (33), in the system model, the primary side series resonance inductance LfPrimary side parallel resonance capacitor CfPrimary side series compensation capacitor CPEquivalent resistance R of primary coilPSecondary coil equivalent resistance RSSecondary side resonance compensation capacitor CSAnd a booster circuit inductor LbCapacitor Cr、CoLoad resistance RLThe isoelectric parameters are known, and no switch tube S is provided5Applying a driving signal and self-inductance L of the primary coilPThe theoretical load voltage is determined to be self-induced along with the secondary coilSAnd/or the primary and secondary coil mutual inductance M.
In some embodiments, determining the primary and secondary coil mutual inductances and the secondary coil self-inductance based on the second theoretical inverted steady-state output current and the measured second inverted steady-state output current value, the theoretical load voltage, and the measured load voltage value comprises:
calculating the current square of the difference between the first theoretical inversion steady-state output current and the second theoretical inversion steady-state output current;
calculating the voltage square of the difference between the theoretical load voltage and the load voltage value according to the theoretical load voltage and the load voltage value;
establishing an objective function taking the average value of the square of the current and the square of the voltage to be minimum as an optimization target;
and solving the target function by using a predetermined function solving method to obtain the primary and secondary side coil mutual inductance and the secondary side coil self-inductance.
In this embodiment, in order to identify the self inductance of the secondary coil and the mutual inductance of the primary and secondary coils in the state of being switched into the load, the current square of the difference between the two is determined according to the second theoretical inversion steady-state output current and the second inversion steady-state output current value, the voltage square of the difference between the two is determined according to the theoretical load voltage and the load voltage value, and an objective function is constructed as an optimization objective with the average value of the current square and the voltage square being the minimum, where the objective function is expressed as:
wherein if(T2)meaIs T2At that time, the output current value of the high-frequency inverter measured by the current sensor. i.e. if(T2) Is T2Second theory of time inverts steady state output current, which is self-induced with secondary winding LsAnd the mutual inductance M of the primary coil and the secondary coil changes; u shapeoLIs T2Theoretical load voltage at time, UoL_meaIs T2At that time, the load voltage value measured by the voltage sensor is used.
By solving the objective function shown in the formula (34), the optimal secondary coil self-inductance L is foundsAnd the mutual inductance M of the original secondary coil enables the average value of the current square and the voltage square to be minimum, and then the optimal self inductance of the secondary coil and the optimal mutual inductance of the original secondary coil are the determined self inductance of the secondary coil and the determined mutual inductance of the original secondary coil, so that the identification of the self inductance of the secondary coil and the mutual inductance of the original secondary coil is realized.
In some embodiments, the objective function shown in equation (34) may be solved using a genetic algorithm to obtain the optimal self inductance of the secondary coil and the primary and secondary coil mutual inductances. The method for solving the objective function by utilizing the genetic algorithm specifically comprises the following steps:
under the state that a direct current power supply is switched on and a load is switched on, initializing a system model according to various circuit parameters of a wireless power transmission network, a measured second inversion steady-state output current value and a measured load voltage value, initializing a population by taking self inductance of a secondary coil and mutual inductance of a primary coil and a secondary coil as particles, and initializing parameters of a genetic algorithm, including setting the population scale, iteration times, cross probability, variation probability and the like; calculating for each individual in the population a fitness value as a function of fitness value according to equation (34) reflecting how close the theoretical calculated value is to the actual measured value; after calculation, sorting and screening the fitness value corresponding to each individual, setting a generation ditch of each generation, and selecting a parent generation and a parent generation from the individuals, wherein the higher the fitness value is, the higher the possibility of selection is; carrying out cross mutation on the selected parent and the mother generation according to the cross probability and the mutation probability to generate new filial generations; and (3) forming a new generation of population by the new filial generation and the individuals survived from the previous generation, executing the process until the iteration times are reached or the iteration termination condition is met, and obtaining the optimal individuals in the population, wherein the optimal individuals are the optimal self inductance of the secondary coil and the initial secondary coil mutual inductance. The above is a basic process for solving the optimal solution of the objective function by using the genetic algorithm, and the present embodiment does not explain the detailed principles and processes of the genetic algorithm.
In order to verify the effectiveness of the coupling parameter identification method of the present specification, simulation analysis is performed on the method. In some embodiments, a system model is established based on a Matlab/Simulink simulation platform, and simulation circuit parameters of the system model are set as shown in table 1:
TABLE 1 simulation Circuit parameters of System model
In the simulation process, the harmonic frequency n is set to be 101, and the primary coil self-inductance LPIs 74uH, secondary coil self-inductance LSThe value is 140uH, and the mutual inductance M of the primary coil and the secondary coil is 22 uH. According to the method of the specification, under the condition that a direct-current power supply is switched on and a load is switched off, the self-inductance of a primary coil is identified to be 73.9 uH; under the conditions that a direct-current power supply is switched on and a load is switched on, the self inductance of the secondary side coil is recognized to be 141uH, and the mutual inductance of the primary side coil and the secondary side coil is recognized to be 22 uH; it can be seen that the coupling parameter identified using the method of the present embodiment is very close to the actual value of the coupling parameter. In order to further verify the accuracy and the applicability of the method, under different working conditions (for example, changing the relative positions of the primary coil and the secondary coil, etc.), the method of the embodiment is used to identify the coupling parameters, and the identification results are shown in table 2:
TABLE 2 coupling parameter identification results
According to the comparison data of the identification results shown in table 2, the calculated identification values of the coupling parameters are very close to the actual values under different working conditions, and the error rates of the self-inductance of the primary coil, the self-inductance of the secondary coil and the mutual inductance identification of the primary coil and the secondary coil are respectively 0.15%, 8.3% and 1.5% at most.
On one hand, in the coupling parameter identification method provided by this embodiment, in a state where a direct current power supply is turned on and a load is not connected, after a system enters a steady state, a first theoretical inversion steady-state output current with a primary coil self-inductance as a variable is determined, an objective function is established according to the first theoretical inversion steady-state output current and a measured first inversion steady-state output current value, and an optimal primary coil self-inductance is determined by solving the objective function; on the other hand, under the state that a direct-current power supply is switched on and a load is switched on, after the system enters a steady state, second theoretical inversion steady-state output current and theoretical load voltage which take the self-inductance of the secondary side coil and the mutual inductance of the primary side coil as variables are determined, an objective function is established according to the second theoretical inversion steady-state output current, the measured second inversion steady-state output current value, the theoretical load voltage and the measured load voltage value, and the optimal self-inductance of the secondary side coil and the mutual inductance of the primary side coil are determined by solving the objective function. The coupling parameter identification method is suitable for an LCC-S type MC-WPT system, and when the transmission performance of the system is changed due to the change of the relative position of a primary coil and a secondary coil of the system or the change of the environment, the coupling parameter can be accurately identified, and then compensation or debugging is performed based on the current coupling parameter, so that the system can be ensured to keep good transmission performance.
It should be noted that the method of one or more embodiments of the present disclosure may be performed by a single device, such as a computer or server. The method of the embodiment can also be applied to a distributed scene and completed by the mutual cooperation of a plurality of devices. In such a distributed scenario, one of the devices may perform only one or more steps of the method of one or more embodiments of the present disclosure, and the devices may interact with each other to complete the method.
It should be noted that the above description describes certain embodiments of the present disclosure. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing may also be possible or may be advantageous.
As shown in fig. 4, an embodiment of the present specification further provides a coupling parameter identification apparatus, including:
the first coupling parameter identification module is used for determining a first theoretical inversion steady-state output current under the conditions of switching on a direct-current power supply and switching off a load, and determining the self-inductance of the primary coil according to the first theoretical inversion steady-state output current and a measured first inversion steady-state output current value;
and the second coupling parameter identification module is used for determining a second theoretical inversion steady-state output current and a theoretical load voltage under the conditions of switching on the direct-current power supply and switching on the load, and determining primary and secondary mutual inductance and secondary coil self-inductance according to the second theoretical inversion steady-state output current, a measured second inversion steady-state output current value, the theoretical load voltage and a measured load voltage value.
For convenience of description, the above devices are described as being divided into various modules by functions, and are described separately. Of course, the functionality of the modules may be implemented in the same one or more software and/or hardware implementations in implementing one or more embodiments of the present description.
The apparatus of the foregoing embodiment is used to implement the corresponding method in the foregoing embodiment, and has the beneficial effects of the corresponding method embodiment, which are not described herein again.
As shown in fig. 5, an embodiment of the present disclosure further provides a wireless power transmission system, which includes a coupling parameter identification device, and during a field debugging process of the wireless power transmission system, or when a relative position of an original secondary coil changes, or an environment of the system changes, the coupling parameter identification device may be used to identify a current primary coil self-inductance, a secondary coil self-inductance, and an original secondary mutual inductance, so as to perform compensation or debugging according to an identified coupling parameter, so as to ensure a transmission performance of the wireless power transmission system.
Those of ordinary skill in the art will understand that: the discussion of any embodiment above is meant to be exemplary only, and is not intended to intimate that the scope of the disclosure, including the claims, is limited to these examples; within the spirit of the present disclosure, features from the above embodiments or from different embodiments may also be combined, steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present description as described above, which are not provided in detail for the sake of brevity.
In addition, well-known power/ground connections to Integrated Circuit (IC) chips and other components may or may not be shown in the provided figures, for simplicity of illustration and discussion, and so as not to obscure one or more embodiments of the disclosure. Furthermore, devices may be shown in block diagram form in order to avoid obscuring the understanding of one or more embodiments of the present description, and this also takes into account the fact that specifics with respect to implementation of such block diagram devices are highly dependent upon the platform within which the one or more embodiments of the present description are to be implemented (i.e., specifics should be well within purview of one skilled in the art). Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the disclosure, it should be apparent to one skilled in the art that one or more embodiments of the disclosure can be practiced without, or with variation of, these specific details. Accordingly, the description is to be regarded as illustrative instead of restrictive.
While the present disclosure has been described in conjunction with specific embodiments thereof, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art in light of the foregoing description. For example, other memory architectures (e.g., dynamic ram (dram)) may use the discussed embodiments.
It is intended that the one or more embodiments of the present specification embrace all such alternatives, modifications and variations as fall within the broad scope of the appended claims. Therefore, any omissions, modifications, substitutions, improvements, and the like that may be made without departing from the spirit and principles of one or more embodiments of the present disclosure are intended to be included within the scope of the present disclosure.
Claims (5)
1. The coupling parameter identification method is applied to a wireless power transmission system, wherein the wireless power transmission system comprises a high-frequency inverter, and the coupling parameter identification method is characterized by comprising the following steps:
under the states of switching on a direct-current power supply and switching off a load, after a system enters a stable state, determining a first falling edge moment of a first period of the output voltage of the high-frequency inverter;
determining a first theoretical inversion steady-state output current of the first falling edge moment according to a system model of the wireless power transmission system;
establishing a first objective function taking the square of the difference between the first theoretical inversion steady-state output current and the measured first inversion steady-state output current as a first optimization objective when the square of the difference reaches a minimum;
solving the first objective function by using a predetermined function solving method to obtain the self-inductance of the primary coil corresponding to the first optimization objective;
under the state that a direct-current power supply is switched on and a load is switched on, after a system enters a stable state, determining a second falling edge moment of a first period of the output voltage of the high-frequency inverter;
determining a second theoretical inversion steady-state output current and a theoretical load voltage at the second falling edge moment according to the system model;
calculating the current square of the difference between the second theoretical inversion steady-state output current and the measured second inversion steady-state output current value according to the second theoretical inversion steady-state output current and the measured second inversion steady-state output current value;
calculating the voltage square of the difference between the theoretical load voltage and the measured load voltage value according to the theoretical load voltage and the measured load voltage value;
establishing a second objective function with a minimum average of the square of the current and the square of the voltage as a second optimization objective;
and solving the second objective function by using a predetermined function solving method to obtain the primary and secondary side mutual inductance and the secondary side coil self-inductance corresponding to the second optimization objective.
2. The method of claim 1, wherein the first theoretical inverting steady-state output current varies with the primary coil self-inductance with other circuit parameters of the system model being known.
3. The method of claim 1, wherein the second theoretical inverting steady state output current varies with the secondary coil self inductance and/or primary secondary coil mutual inductance, and the theoretical load voltage varies with the secondary coil self inductance and/or primary secondary coil mutual inductance, with other circuit parameters of the system model being known.
4. Coupling parameter recognition device is applied to wireless power transmission system, wireless power transmission system includes high frequency inverter, its characterized in that includes:
the first coupling parameter identification module is used for determining a first falling edge moment of a first period of the output voltage of the high-frequency inverter after a system enters a stable state under the states of switching on a direct-current power supply and switching off a load; determining a first theoretical inversion steady-state output current of the first falling edge moment according to a system model of the wireless power transmission system; establishing a first objective function taking the square of the difference between the first theoretical inversion steady-state output current and the measured first inversion steady-state output current as a first optimization objective when the square of the difference reaches a minimum; solving the first objective function by using a predetermined function solving method to obtain the self-inductance of the primary coil corresponding to the first optimization objective;
the second coupling parameter identification module is used for determining a second falling edge moment of a first period of the output voltage of the high-frequency inverter after the system enters a steady state in the state of switching on the direct-current power supply and switching in the load; determining a second theoretical inversion steady-state output current and a theoretical load voltage at the second falling edge moment according to the system model; calculating the current square of the difference between the second theoretical inversion steady-state output current and the measured second inversion steady-state output current value according to the second theoretical inversion steady-state output current and the measured second inversion steady-state output current value; calculating the voltage square of the difference between the theoretical load voltage and the measured load voltage value according to the theoretical load voltage and the measured load voltage value; establishing a second objective function with a minimum average of the square of the current and the square of the voltage as a second optimization objective; and solving the second objective function by using a predetermined function solving method to obtain the primary and secondary side mutual inductance and the secondary side coil self-inductance corresponding to the second optimization objective.
5. A wireless power transfer system comprising the coupling parameter identification apparatus of claim 4.
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