CN116054424A - Dynamic mutual inductance online evaluation method based on wireless power transmission system - Google Patents

Dynamic mutual inductance online evaluation method based on wireless power transmission system Download PDF

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CN116054424A
CN116054424A CN202211620682.7A CN202211620682A CN116054424A CN 116054424 A CN116054424 A CN 116054424A CN 202211620682 A CN202211620682 A CN 202211620682A CN 116054424 A CN116054424 A CN 116054424A
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mutual inductance
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coil
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孙向东
赵记锋
任碧莹
陈泽驰
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Xian University of Technology
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
    • G—PHYSICS
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    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
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    • G01—MEASURING; TESTING
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    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/80—Circuit arrangements or systems for wireless supply or distribution of electric power involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H02J50/90—Circuit arrangements or systems for wireless supply or distribution of electric power involving detection or optimisation of position, e.g. alignment
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
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Abstract

The invention discloses a dynamic mutual inductance online evaluation method based on a wireless power transmission system, which is implemented according to the following steps: step 1: acquiring inherent parameters of a wireless power transmission system; step 2: setting a receiving coil side direct current load voltage change threshold and a load voltage change time threshold thereof, and measuring the load voltage change amount and the time interval amount of the detection voltage so as to determine whether the receiving coil position is changed; step 3: if the position of the receiving coil is not changed, repeating the step 2; if the position of the receiving coil is changed, detecting each phase of circuit in sequence, and acquiring mutual inductance coefficients by combining the inherent parameters of the step 1, wherein the step 4 is as follows: and (3) evaluating the accuracy of the wireless power transmission system according to the mutual inductance coefficient of each phase of circuit obtained in the step (3). The method has the advantages of simple structure and convenient control, and can ensure the online accurate estimation of the mutual inductance between the transmitting coil and the receiving coil when the position of the receiving coil in the omnidirectional WPT system is changed.

Description

Dynamic mutual inductance online evaluation method based on wireless power transmission system
Technical Field
The invention belongs to the technical field of radio transmission, and relates to a dynamic mutual inductance online evaluation method based on a radio energy transmission system.
Background
Wireless power transfer technology (Wireless Power Transfer, WPT) is a technology that uses a spatial electromagnetic field, microwaves, or other medium as a power carrier to enable power to be transferred from a power source to powered devices without direct contact through wires. The charging device has the advantages of being capable of being charged at any time, free of direct contact, safe, reliable and the like. Wireless power transmission is one of the current and even future hot spot research directions and has been applied in many fields such as portable electronic devices, charged automobiles, medical devices, military fields, etc. However, the conventional wireless charging technology generally adopts a "patch-type" charging mode, and when in use, a receiving coil in the charging device must be strictly aligned with a transmitting coil on the charging plate, so that the degree of freedom of charging is greatly limited.
In order to improve the degree of freedom of charging, an omnidirectional WPT technology is generated, and the technology enables the charging equipment to obtain higher degree of freedom in the wireless charging process through improving a coil structure and a circuit topology in the traditional 'patch-type' WPT technology. Among them, the omnidirectional WPT system based on the three-phase orthogonal transmitting coil is being widely studied because of its simple structure and easy control. The system realizes wireless power transmission of the receiving coil at any position in a certain range by controlling the amplitude, the phase and the frequency of exciting current in the transmitting coil. However, the current omnidirectional WPT system has the problem that the system is difficult to efficiently transmit electric energy due to the position deviation of the transmitting coil and the receiving coil, and the root cause of the problem is that mutual inductance between coils caused by the position deviation of the transmitting coil and the receiving coil is changed, so that the electric energy transmission effect of the system is directly affected, and then stable and efficient electric energy cannot be provided for charging equipment.
Therefore, accurate estimation of mutual inductance between the transmitting coil and the receiving coil is a precondition for realizing efficient wireless power transmission. The existing mutual inductance estimation method is suitable for static mutual inductance estimation or dynamic mutual inductance estimation with larger difficulty and larger estimation error. Therefore, the invention provides a high-precision dynamic mutual inductance online estimation method, which meets the real-time online estimation of mutual inductance when the load position is changed, and lays a foundation for improving the efficient electric energy transmission of the WPT system.
Disclosure of Invention
The invention aims to provide a dynamic mutual inductance online evaluation method based on a wireless power transmission system, which solves the problems of the prior art that the dynamic mutual inductance evaluation method has larger difficulty and larger evaluation error.
The technical scheme adopted by the invention is a dynamic mutual inductance online evaluation method based on a wireless power transmission system, wherein the wireless power transmission system is a multiphase synchronous BUCK circuit, and the method is implemented according to the following steps:
step 1: acquiring inherent parameters of a wireless power transmission system;
step 2: setting a receiving coil side direct current load voltage change threshold and a load voltage change time threshold thereof, and measuring the load voltage change amount and the time interval amount of the detection voltage so as to determine whether the receiving coil position is changed;
step 3: if the position of the receiving coil is not changed, repeating the step 2; if the position of the receiving coil is changed, each phase of circuit is detected in sequence, the mutual inductance coefficient is obtained by combining the inherent parameters of the step 1,
step 4: and (3) evaluating the accuracy of the wireless power transmission system according to the mutual inductance coefficient of each phase of circuit obtained in the step (3).
The invention is also characterized in that:
intrinsic parameters of the wireless power transfer system include LCC compensation network inductance L fi Equivalent resistance R of receiving coil RX Load resistor R L Values.
The specific process of the step 2 is as follows: setting the interface according to the inherent parameters of the step 1Receiving coil side direct current load voltage change threshold sigma and load voltage change time threshold zeta, detecting system receiving coil side direct current load voltage condition in real time, and determining load voltage change delta U out And detecting a time interval amount Δt of the voltage, wherein:
ΔU out ＝U out (t 2 )-U out (t 1 ) (1)
ΔT＝t 2 -t 1 (2)
in U out (t 2 ) U and U out (t 1 ) Respectively the current t 2 Sampling time and last t 1 Receiving coil side DC load voltage U detected at sampling time out A voltage amplitude;
when DeltaU out If the time interval is more than or equal to sigma, further judging the relation between the time interval and the load voltage change time threshold, otherwise repeating the steps; and when the delta T is more than or equal to zeta, judging that the position of the receiving coil is changed.
The specific process of the step 3 is as follows: first, the duty ratio of the first synchronous BUCK circuit is set to be a fixed duty ratio between 0 and 100%, and the amplitude U of the DC load voltage at the receiving coil side is used for out The first synchronous BUCK circuit outputs a DC voltage amplitude U buck1 Obtaining mutual inductance parameters M of a first phase through a mutual inductance model algorithm 1 The method comprises the steps of carrying out a first treatment on the surface of the Then, the duty ratio of the first synchronous BUCK circuit is set to 0, and after the output DC voltage amplitude is detected to be reduced to zero, the duty ratio of the second synchronous BUCK circuit is set to be a fixed duty ratio between 0 and 100%, and the DC load voltage amplitude U at the receiving coil side is detected out Output DC voltage amplitude U of second phase synchronous BUCK circuit buck2 Obtaining mutual inductance parameters M of the second phase through a mutual inductance model algorithm 2 The method comprises the steps of carrying out a first treatment on the surface of the And finally, according to the detection process of the second phase, detecting the rest synchronous BUCK circuits in sequence to obtain the mutual inductance coefficient.
Before the step 3 is implemented, the duty ratio of the synchronous BUCK circuit at the transmitting coil side is required to be set to be 0, so that no current input to the transmitting coil is ensured, and the output voltage of the system is zero.
The mutual inductance model algorithm is as follows:
Figure BDA0004001943860000041
wherein M is i Is the mutual inductance coefficient, U out For receiving coil side DC load voltage, R RX R is the equivalent resistance of the receiving coil rec_eq Represents the equivalent resistance, L, at the dashed line box in the circuit shown in FIG. 2 fi To compensate for network inductance, U i For the output voltage of the port of each phase inverter, U bucki The voltage is outputted to the synchronous BUCK circuit.
The derivation process of the mutual inductance model algorithm is as follows:
the synchronous BUCK circuit outputs a voltage relationship:
U bucki ＝D i ·U dc (4)
wherein D is i For the duty cycle of the i-th synchronous BUCK circuit power switching tube 1, i=1, 2.
The input voltage U of the inverter port can be obtained according to kirchhoff voltage law i The expression:
U i ＝jωL fi I fi +U fi (5)
in designing an LCC compensation network, to ensure that the input transmit coil current is not affected by load variations, the following design principles are typically based:
ω 2 L fi C fi ＝1 (6)
ω 2 (L TXi -L fi )C i ＝1 (7)
ω 2 L RX C 4 ＝1 (8)
the induced electromotive force between the ith transmitting coil and the receiving coil is related to the mutual inductance and the induced current between the ith transmitting coil and the receiving coil, wherein the ith transmitting coil corresponds to the induced electromotive force U of the receiving coil TXi_RX And the receiving coil corresponds to the induction electromotive force U of the ith transmitting coil RX_TXi The method comprises the following steps of:
U TXi_RX ＝jωM i I i (9)
U RX_TXi ＝jωM i I 4 (10)
in the formulas (9) and (10), I i 、I 4 Respectively, the current flowing into the i-th phase transmitting coil and the current induced by the receiving coil;
capacitor C in LCC compensation network can be obtained according to kirchhoff voltage law fi Port voltage:
Figure BDA0004001943860000051
the capacitor C can be obtained by combining the capacitor C (5) with the capacitor C (11) fi Port voltage:
Figure BDA0004001943860000052
it is known that the transmitting coil current is only output by the inverter port at voltage U i And compensating network inductance L fi And the system frequency omega, the current of the transmitting coil can be obtained by solving:
Figure BDA0004001943860000053
the receiving side can solve according to kirchhoff's voltage law:
Figure BDA0004001943860000054
wherein R is rec_eq For the equivalent resistance in the dashed line box of fig. 2, it can be obtained by the impedance transformation of the full bridge rectifier:
Figure BDA0004001943860000055
the equivalent circuit relation formula of the omnidirectional WPT system obtained by popularizing the formula (12) and the formula (14) to a three-phase transmitting coil system is as follows:
Figure BDA0004001943860000056
the receive coil current can be solved by equation (16):
Figure BDA0004001943860000061
from equation (17), it is known that the receiving coil current has a dense and inseparable relationship with the three-phase transmitting coil mutual inductance and the transmitting coil current. In order to simplify the mutual inductance estimation model, it is assumed that only one transmitting coil participates in operation at the same time, and it is assumed that only the transmitting coil i operates, a simplified mutual inductance parameter estimation model can be obtained:
Figure BDA0004001943860000062
as can be seen from equation (18), if the above model is used to realize online estimation of the mutual inductance parameters, the high-frequency current of the receiving coil and the transmitting coil needs to be collected, but the system frequency operates at hundreds of kilohertz, even several megahertz and tens of megahertz, which increases the difficulty in identifying the mutual inductance parameters and increases the hardware cost of the system.
In order to solve the problems, a fundamental wave analysis method of a circuit is introduced, and the fundamental wave analysis method can be known as follows:
Figure BDA0004001943860000063
in U i_RMS For the i-th phase inverter output voltage U i The effective value of the fundamental voltage of the (I) can be obtained at the same time i_RMS The method comprises the following steps:
Figure BDA0004001943860000064
according to the principle of series circuit voltage division, the effective value U of the input voltage of the port of the synchronous rectification circuit of the receiving side is obtained rec The method comprises the following steps:
Figure BDA0004001943860000065
according to fundamental wave analysis method, the relation between the effective value of the input voltage and the output DC voltage of the synchronous rectification circuit port is as follows:
Figure BDA0004001943860000066
the mutual inductance model algorithm can be obtained by the combined type (19) to the formula (22):
Figure BDA0004001943860000071
in formula (3), U i Output voltage amplitude for i-th phase inverter port, U bucki The voltage is outputted to the i-th phase pre-stage synchronous BUCK circuit.
When the multiphase synchronous BUCK circuit acquires each mutual inductance coefficient, the fixed duty ratio is set to be 70%.
According to the dynamic mutual inductance online estimation method, mutual inductance estimation is carried out according to the load direct-current voltage at the receiving coil side, the direct-current voltage output by the front-stage BUCK circuit at the transmitting coil side and the inherent parameters of the circuit, so that the problem that the mutual inductance change caused by the position movement of the receiving coil in an omnidirectional WPT system is difficult to estimate online in real time can be solved. The method does not need to detect the high-frequency current of the transmitting coil and the receiving coil, and has the advantages of simple structure and convenient control. The method can ensure the online accurate estimation of the mutual inductance between the transmitting coil and the receiving coil when the position of the receiving coil in the omnidirectional WPT system is changed, and is beneficial to realizing the real-time and efficient electric energy transmission of the omnidirectional WPT system.
Drawings
Fig. 1 is a schematic diagram of the relative positions of a transmitting coil and a receiving coil of a WPT system based on a three-phase quadrature transmitting coil in an embodiment of the present invention;
fig. 2 is an equivalent circuit diagram of an omnidirectional WPT system based on a three-phase LCC-S compensation network in an embodiment of the present invention;
figure 3 is a circuit equivalent diagram of a single phase in an omnidirectional WPT system;
FIG. 4 is a flow chart of dynamic mutual inductance online estimation for an omnidirectional wireless power transfer system;
FIG. 5 is a waveform diagram of the corresponding output DC voltage of the three-phase synchronous BUCK circuit during mutual inductance online estimation;
FIG. 6 shows the mutual inductance M between the transmitter coil 1 and the receiver coil when the receiver coil is at position 1 1 Simulating an estimation result graph;
FIG. 7 shows the mutual inductance M between the transmitter coil 2 and the receiver coil when the receiver coil is at position 1 2 Simulating an estimation result graph;
FIG. 8 shows the mutual inductance M of the transmitting coil 3 and the receiving coil when the receiving coil is at position 1 3 Simulating an estimation result graph;
fig. 9 shows the mutual inductance M of the transmitting coil 1 and the receiving coil when the receiving coil is at position 2 1 Simulating an estimation result graph;
fig. 10 shows the mutual inductance parameter M of the transmitting coil 2 and the receiving coil when the receiving coil is at position 2 2 Simulating an estimation result graph;
FIG. 11 shows the mutual inductance M of the transmitting coil 3 and the receiving coil when the receiving coil is at position 2 3 And (5) simulating an estimation result graph.
Detailed Description
The invention will be described in detail below with reference to the drawings and the detailed description.
For ease of explanation, the wireless power transfer system in the present application employs a WPT system based on three-phase quadrature transmit coils, the basic parameters of the WPT system circuit are shown in table 1.
Table 1 basic parameters of WPT system circuits
Figure BDA0004001943860000081
The relative positions of the transmitting coil and the receiving coil of the WPT system of the three-phase orthogonal transmitting coil are shown in fig. 1, and the transmitting coil can be known1 is located in an XOY plane; the transmitting coil 2 is positioned on the XOZ plane; the transmitting coil 3 is positioned on the YOZ plane; the receiving coil is positioned in the center of the transmitting coil, and the elevation angle of the receiving coil is delta xy Azimuth angle of
Figure BDA0004001943860000091
An equivalent circuit diagram of the omnidirectional WPT system based on the three-phase LCC-S compensation network is shown in figure 2, wherein U is as follows dc For the direct current input voltage of the system, I dc The direct current is input; u (U) 1 、U 2 、U 3 Respectively representing the port output voltages of the inverters of each phase; u (U) f1 、U f2 、U f3 Representing the capacitance C in each LCC compensation network f1 、C f2 、C f3 Is a port voltage of (a); i f1 、I f2 、I f3 Respectively representing the port output currents of the inverters of each phase; i 1 、I 2 、I 3 Respectively representing the current flowing into each phase of transmitting coil; i 4 Representing the current induced by the receiving coil; u (U) out For the system receiving coil side DC load voltage, I out Is the load current; q (Q) bucki_1 、Q bucki_2 (i=1, 2, 3) is a power switch of three groups of synchronous BUCK circuits; q (Q) i1 ～Q i4 Power switches for three sets of single-phase bridge inverters; q (Q) rec1 ～Q rec4 A power switch for a synchronous rectification circuit at a receiving side; c (C) dc A filter capacitor is input for a direct current power supply; l (L) buck1 、L buck2 、L buck3 The inductors of the synchronous BUCK circuits are respectively; u (U) buck1 、U buck2 、U buck3 Respectively outputting voltages for the synchronous BUCK circuits; l (L) TX1 、L TX2 、L TX3 The inductance of each phase of transmitting coil is respectively; l (L) f1 、C f1 、C 1 LCC compensation network, L, constituting the transmitting coil 1 f2 、C f2 、C 2 LCC compensation network, L, constituting the transmitting coil 2 f3 、C f3 、C 3 An LCC compensation network constituting the transmitting coil 3; c (C) 4 A compensation capacitance for the receiving coil; r is R TX1 、R TX2 、R TX3 Respectively are provided withParasitic resistance for each phase of transmit coil; r is R RX Parasitic resistance of the receiving coil; r is R L Is an equivalent load resistance; r is R rec_eq Equivalent resistance of the broken line portion; m is M 1 、M 2 、M 3 Respectively representing mutual inductance between each phase of transmitting coil and receiving coil; m is M 12 、M 23 、M 13 Representing the mutual inductance between the transmit coils of each phase.
Since the three-phase transmitting coils are orthogonal to each other, cross coupling between the transmitting coils can be neglected, so that mutual inductance M between the three-phase transmitting coils 12 、M 23 、M 13 May be equivalent to 0.
To simplify the calculation process, the single-phase circuit of fig. 3 is used for analysis:
the output voltage relationship of synchronous BUCK circuits is known:
U bucki ＝D i ·U dc (24)
wherein D is i For the duty cycle of the i-th synchronous BUCK circuit power switch tube 1, i=1, 2 and 3.
The input voltage U of the inverter port can be obtained according to kirchhoff voltage law i The expression:
U i ＝jωL fi I fi +U fi (25)
in designing an LCC compensation network, to ensure that the input transmit coil current is not affected by load variations, the following design principles are typically based:
ω 2 L fi C fi ＝1 (26)
ω 2 (L TXi -L fi )C i ＝1 (27)
ω 2 L RX C 4 ＝1 (28)
the induced electromotive force between the ith transmitting coil and the receiving coil is related to the mutual inductance and the induced current between the ith transmitting coil and the receiving coil, wherein the ith transmitting coil corresponds to the induced electromotive force U of the receiving coil TXi_RX And the receiving coil corresponds to the induction electromotive force U of the ith transmitting coil RX_TXi The method comprises the following steps of:
U TXi_RX ＝jωM i I i (29)
U RX_TXi ＝jωM i I 4 (30)
in the formulas (9) and (10), I i 、I 4 The current flowing into the i-th phase transmitting coil and the current induced by the receiving coil are shown, respectively.
Capacitor C in LCC compensation network can be obtained according to kirchhoff voltage law fi Port voltage:
Figure BDA0004001943860000102
the capacitor C can be obtained by combining the capacitor C (5) with the capacitor C (11) fi Port voltage:
Figure BDA0004001943860000103
it is known that the transmitting coil current is only output by the inverter port at voltage U i And compensating network inductance L fi And the system frequency omega, the current of the transmitting coil can be obtained by solving:
Figure BDA0004001943860000111
the receiving side can solve according to kirchhoff's voltage law:
Figure BDA0004001943860000112
wherein R is rec_eq For the equivalent resistance in the dashed line box of fig. 2, it can be obtained by the impedance transformation of the full bridge rectifier:
Figure BDA0004001943860000113
the equivalent circuit relation formula of the omnidirectional WPT system obtained by popularizing the formula (12) and the formula (14) to a three-phase transmitting coil system is as follows:
Figure BDA0004001943860000114
the receive coil current can be solved by equation (16):
Figure BDA0004001943860000115
from equation (17), it is known that the receiving coil current has a dense and inseparable relationship with the three-phase transmitting coil mutual inductance and the transmitting coil current. In order to simplify the mutual inductance estimation model, it is assumed that only one transmitting coil participates in operation at the same time, and it is assumed that only the transmitting coil i operates, a simplified mutual inductance parameter estimation model can be obtained:
Figure BDA0004001943860000116
as can be seen from equation (18), if the above model is used to realize online estimation of the mutual inductance parameters, the high-frequency current of the receiving coil and the transmitting coil needs to be collected, but the system frequency operates at hundreds of kilohertz, even several megahertz and tens of megahertz, which increases the difficulty in identifying the mutual inductance parameters and increases the hardware cost of the system.
In order to solve the problems, a fundamental wave analysis method of a circuit is introduced, and the fundamental wave analysis method can be known as follows:
Figure BDA0004001943860000121
in U i_RMS For the i-th phase inverter output voltage U i The effective value of the fundamental voltage of the (I) can be obtained at the same time i_RMS The method comprises the following steps:
Figure BDA0004001943860000122
according to the voltage division of the series circuitIn principle, the effective value U of the input voltage of the synchronous rectification circuit port of the receiving side can be obtained rec The method comprises the following steps:
Figure BDA0004001943860000123
according to fundamental wave analysis method, the relation between the effective value of the input voltage and the output DC voltage of the synchronous rectification circuit port is as follows:
Figure BDA0004001943860000124
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the mutual inductance model can be obtained by the combined type (19) to the formula (22):
Figure BDA0004001943860000125
in formula (3), U i Output voltage amplitude for i-th phase inverter port, U bucki The voltage is outputted to the i-th phase pre-stage synchronous BUCK circuit.
The method for estimating the mutual inductance parameters on line greatly reduces the difficulty of the system mutual inductance on line estimation and only needs to output direct current voltage U to the synchronous BUCK circuit bucki DC load voltage U at system receiving coil side out And the detection is carried out without an additional sampling circuit, so that the hardware cost of the system is reduced. Because the sampling amounts are all direct-current voltage values, high-frequency alternating-current amounts do not exist, so that the mutual inductance parameter on-line estimation error is small and the precision is high. In practical system application, the receiving coil side is usually a charging control system with Bluetooth or WLAN communication function, and because the moving speed of the receiving coil is relatively slow, the direct current load voltage data collected by the receiving coil side can be timely sent to the transmitting coil side control system for mutual inductance estimation through the communication technology, so that voltage information exchange between transmitting equipment and receiving equipment is ensured, and the feasibility of the dynamic mutual inductance online estimation method is ensured.
The embodiment of the dynamic mutual inductance online evaluation method based on the wireless power transmission system provided by the invention is shown in fig. 4, and the specific implementation steps are as follows:
step 1, determining a system inherent parameter LCC compensation network inductance L fi Equivalent resistance R of receiving coil RX Load resistor R L The above parameters are readily available for coil and compensation network design.
Step 2, setting a receiving coil side DC load voltage change threshold sigma and a load voltage change time threshold zeta, detecting the receiving coil side DC load voltage condition of the system in real time, and determining the load voltage change delta U out And detecting a time interval amount Δt of the voltage, wherein:
ΔU out ＝U out (t 2 )-U out (t 1 ) (44)
ΔT＝t 2 -t 1 (45)
in U out (t 2 ) U and U out (t 1 ) Respectively the current t 2 Sampling time and last t 1 Receiving coil side DC load voltage U detected at sampling time out The voltage amplitude.
And judging the relation between the direct current load voltage variation quantity at the receiving coil side and the load voltage variation threshold value. When DeltaU out And when the delta T is more than or equal to sigma, further judging the relation between the time interval quantity and the load voltage change time threshold value, and when the delta T is more than or equal to zeta, judging that the position of the receiving coil is changed.
And step 3, determining whether the position of the receiving coil changes or not by the step 2, and if the position of the receiving coil changes, on-line estimation of mutual inductance between each transmitting coil and each receiving coil of the WPT system at the current position is needed.
When mutual inductance online estimation is carried out, the system firstly sets the duty ratio of the synchronous BUCK circuit at the transmitting coil side to be 0, so that no current input of the three-phase transmitting coil is ensured, and the output voltage of the system is zero.
In order to ensure that the operation is finished, the output voltage of the three-phase synchronous BUCK circuit needs to be detected, and when the output voltage is all zero, a sequential detection link is carried out.
First, the duty ratio of the first synchronous BUCK circuit is set to a fixed duty ratio of 0-100%, as shown in FIG. 5, and 70% in this embodiment, and the DC load voltage amplitude U at the receiving coil side of the detection system is set out The first synchronous BUCK circuit outputs a DC voltage amplitude U buck1 Using equation (20) to estimate the mutual inductance parameter M between the transmitter coil 1 and the receiver coil 1 As shown in fig. 6;
setting the duty ratio of the first synchronous BUCK circuit to 0 after the first group of mutual inductance parameters are successfully estimated, and setting the duty ratio of the second synchronous BUCK circuit to a fixed duty ratio between 0 and 100% after detecting that the amplitude of the output direct current voltage is reduced to zero, as shown in FIG. 5, wherein the duty ratio is set to 70% in the embodiment; meanwhile, the detection system receives the DC load voltage amplitude U at the coil side out Output DC voltage amplitude U of second phase synchronous BUCK circuit buck2 Using equation (20) to estimate the mutual inductance parameter M between the transmitter coil 2 and the receiver coil 2 As shown in fig. 7;
setting the duty ratio of the second phase synchronous BUCK circuit to 0 after the second group of mutual inductance parameters are successfully estimated, and setting the duty ratio of the third phase synchronous BUCK circuit to a fixed duty ratio between 0 and 100% after detecting that the amplitude of the output direct current voltage is reduced to zero, as shown in FIG. 5, wherein the duty ratio is set to 70% in the embodiment; meanwhile, the detection system receives the DC load voltage amplitude U at the coil side out Output DC voltage amplitude U of third phase synchronous BUCK circuit buck3 Using (20) to estimate the mutual inductance parameter M between the transmitting coil 3 and the receiving coil 3 As shown in fig. 8.
And 4, after the mutual inductance parameters between the three-phase transmitting coil and the receiving coil are respectively estimated, returning the system to the step 2, carrying out a new round of detection process on whether the position of the receiving coil changes, and estimating the accuracy of the wireless power transmission system according to the mutual inductance coefficient.
To verify the accuracy of the evaluation of the present invention, the following experiments were specially designed to simulate the verification results.
And carrying out simulation verification on the dynamic mutual inductance estimation of the omnidirectional WPT system in MATLAB, wherein the simulation condition is that the direction of the receiving coil is known, and theoretical mutual inductance values between each transmitting coil and each receiving coil are obtained through theoretical calculation and are used for carrying out comparison analysis with the estimated mutual inductance values. Table 1 is a circuit specific simulation parameter.
When the receiving coil position 1 (0.3M, 45 degrees and 45 degrees) is set in a simulation mode, theoretical mutual inductance values at the position 1 are calculated according to a Neumann formula to be M respectively 1 ＝2.9627μH、M 2 ＝2.3562μH、M 3 = 2.3562 μh. Writing the theoretical mutual inductance parameters into a mutual inductance model of MATLAB as a transmitting coil and receiving coil model at a position 1, entering a voltage sampling link according to the step 1 and the step 2, determining that the position of the receiving coil is changed from the previous position, and entering a step 3 mutual inductance estimation link.
After the step 3 is entered, three synchronous BUCK circuits work in sequence, the simulation result is shown in figure 5, and when the 1 st synchronous BUCK circuit works, the mutual inductance M between the transmitting coil 1 and the receiving coil is estimated 1 The mutual inductance M between the transmitting coil 2, the transmitting coil 3 and the receiving coil can be obtained respectively 2 、M 3 Simulation results are shown in fig. 6 to 8. When only one synchronous BUCK circuit works, the output voltage of other two phases of BUCK is zero, and the mutual inductance estimated values of the two phases tend to infinity, so that when only one synchronous BUCK circuit works, the corresponding mutual inductance estimated value of the other two phases is set to 0, and finally only the mutual inductance value with stable estimation is reserved, and the mutual inductance estimated values at the position 1 are respectively M 1e ＝2.943μH、M 2e ＝2.330μH、M 3e = 2.332 μh, as shown in fig. 6 to 8.
Then, the relative error accuracy between the estimated mutual inductance value at position 1 and the theoretical value is:
Figure BDA0004001943860000151
Figure BDA0004001943860000152
Figure BDA0004001943860000153
the mutual inductance relative error calculated by the formulas (46) to (48) shows that the mutual inductance estimation method has higher precision for the mutual inductance estimation between the receiving coil and each transmitting coil at the position 1.
To further verify the mutual inductance estimation method, the receiving coil is moved to the position 2 (0.3M, 30 degrees, 60 degrees), and the theoretical calculated mutual inductance values are M respectively 1 ＝3.2594μH、M 2 ＝2.1032μH、M 3 = 1.2946 μh. Simulation results in mutual inductance estimates at position 2 of M 1e ＝3.233μH、M 2e ＝2.086μH、M 3e = 1.286 μh, as shown in fig. 9 to 11.
Thus, the relative error accuracy between the mutual inductance estimate and the theoretical value at position 2 is:
Figure BDA0004001943860000161
Figure BDA0004001943860000162
Figure BDA0004001943860000163
as can be seen from the mutual inductance relative errors calculated by the formulas (49) to (51), the mutual inductance estimation method also has high accuracy for the mutual inductance estimation between the receiving coil and each transmitting coil at the position 2.
Therefore, the simulation work proves that the dynamic mutual inductance estimation method adopted by the invention has higher accuracy, which lays a solid foundation for the efficiency optimization control of the omnidirectional WPT system.

Claims (8)

1. The dynamic mutual inductance online evaluation method based on the wireless power transmission system is characterized in that the method is implemented according to the following steps:
step 1: acquiring inherent parameters of a wireless power transmission system;
step 2: setting a receiving coil side direct current load voltage change threshold and a load voltage change time threshold thereof, and measuring the load voltage change amount and the time interval amount of the detection voltage so as to determine whether the receiving coil position is changed;
step 3: if the position of the receiving coil is not changed, repeating the step 2; if the position of the receiving coil is changed, each phase of circuit is detected in sequence, the mutual inductance coefficient is obtained by combining the inherent parameters of the step 1,
step 4: and (3) evaluating the accuracy of the wireless power transmission system according to the mutual inductance coefficient of each phase of circuit obtained in the step (3).
2. The method for online evaluation of dynamic mutual inductance based on wireless power transmission system according to claim 1, wherein the intrinsic parameters of the wireless power transmission system include LCC compensation network inductance L fi Equivalent resistance R of receiving coil RX Load resistor R L Values.
3. The method for online evaluation of dynamic mutual inductance based on wireless power transmission system according to claim 1, wherein the specific process of step 2 is as follows: setting a receiving coil side direct current load voltage change threshold sigma and a load voltage change time threshold zeta according to the inherent parameters of the step 1, detecting the receiving coil side direct current load voltage condition of the system in real time, and determining the load voltage change delta U out And detecting a time interval amount Δt of the voltage, wherein:
ΔU out ＝U out (t 2 )-U out (t 1 ) (52)
ΔT＝t 2 -t 1 (53)
in U out (t 2 ) U and U out (t 1 ) Respectively the current t 2 Sampling time and last t 1 Receiving coil side DC load voltage U detected at sampling time out A voltage amplitude;
when DeltaU out If the time interval is more than or equal to sigma, further judging the relation between the time interval and the load voltage change time threshold, otherwise repeating the steps; and when the delta T is more than or equal to zeta, judging that the position of the receiving coil is changed.
4. The method for online evaluation of dynamic mutual inductance based on wireless power transmission system according to claim 1, wherein the specific process of step 3 is as follows: first, the duty ratio of the first synchronous BUCK circuit is set to be a fixed duty ratio between 0 and 100%, and the amplitude U of the DC load voltage at the receiving coil side is used for out The first synchronous BUCK circuit outputs a DC voltage amplitude U buck1 Obtaining mutual inductance parameters M of a first phase through a mutual inductance model algorithm 1 The method comprises the steps of carrying out a first treatment on the surface of the Then, the duty ratio of the first synchronous BUCK circuit is set to 0, and after the output DC voltage amplitude is detected to be reduced to zero, the duty ratio of the second synchronous BUCK circuit is set to be a fixed duty ratio between 0 and 100%, and the DC load voltage amplitude U at the receiving coil side is detected out Output DC voltage amplitude U of second phase synchronous BUCK circuit buck2 Obtaining mutual inductance parameters M of the second phase through a mutual inductance model algorithm 2 The method comprises the steps of carrying out a first treatment on the surface of the And finally, according to the detection process of the second phase, detecting the rest synchronous BUCK circuits in sequence to obtain the mutual inductance coefficient.
5. The method for online evaluation of dynamic mutual inductance based on wireless power transmission system according to claim 4, wherein the step 3 is performed by setting the duty ratio of the synchronous BUCK circuit on the transmitting coil side to 0 before implementing, so as to ensure no current input to the transmitting coil and zero system output voltage.
6. The method for online evaluation of dynamic mutual inductance based on wireless power transmission system according to claim 3, wherein the mutual inductance model algorithm is as follows:
Figure FDA0004001943850000021
wherein M is i Is the mutual inductance coefficient, U out For receiving coil side DC load voltage, R RX R is the equivalent resistance of the receiving coil rec_eq Represents the equivalent resistance, L, at the dashed line box of the circuit shown in FIG. 2 fi To compensate for network inductance, U i For the output voltage of the port of each phase inverter, U bucki The voltage is outputted to the synchronous BUCK circuit.
7. The method for online evaluation of dynamic mutual inductance based on wireless power transmission system according to claim 6, wherein the derivation process of the mutual inductance model algorithm is as follows:
the synchronous BUCK circuit outputs a voltage relationship:
U bucki ＝D i ·U dc (55)
wherein D is i For the duty cycle of the i-th synchronous BUCK circuit power switching tube 1, i=1, 2.
The input voltage U of the inverter port can be obtained according to kirchhoff voltage law i The expression:
U i ＝jωL fi I fi +U fi (56)
in designing an LCC compensation network, to ensure that the input transmit coil current is not affected by load variations, the following design principles are typically based:
ω 2 L fi C fi ＝1 (57)
ω 2 (L TXi -L fi )C i ＝1 (58)
ω 2 L RX C 4 ＝1 (59)
the induced electromotive force between the ith transmitting coil and the receiving coil is related to the mutual inductance and the induced current between the ith transmitting coil and the receiving coil, wherein the ith transmitting coil corresponds to the induced electromotive force U of the receiving coil TXi_RX And the receiving coil corresponds to the induction electromotive force U of the ith transmitting coil RX_TXi The method comprises the following steps of:
U TXi_RX ＝jωM i I i (60)
U RX_TXi ＝jωM i I 4 (61)
in the formulas (9) and (10), I i 、I 4 Respectively, the current flowing into the i-th phase transmitting coil and the current induced by the receiving coil;
capacitor C in LCC compensation network can be obtained according to kirchhoff voltage law fi Port voltage:
Figure FDA0004001943850000031
the capacitor C can be obtained by combining the capacitor C (5) with the capacitor C (11) fi Port voltage:
Figure FDA0004001943850000032
it is known that the transmitting coil current is only output by the inverter port at voltage U i And compensating network inductance L fi And the system frequency omega, the current of the transmitting coil can be obtained by solving:
Figure FDA0004001943850000041
the receiving side can solve according to kirchhoff's voltage law:
Figure FDA0004001943850000042
wherein R is rec_eq For the equivalent resistance in the dashed line box of fig. 2, it can be obtained by the impedance transformation of the full bridge rectifier:
Figure FDA0004001943850000043
the equivalent circuit relation formula of the omnidirectional WPT system obtained by popularizing the formula (12) and the formula (14) to a three-phase transmitting coil system is as follows:
Figure FDA0004001943850000044
the receive coil current can be solved by equation (16):
Figure FDA0004001943850000045
the receiving coil current and the three-phase transmitting coil mutual inductance and the transmitting coil current have a dense and inseparable relation according to the formula (17); in order to simplify the mutual inductance estimation model, it is assumed that only one transmitting coil participates in operation at the same time, and it is assumed that only the transmitting coil i operates, a simplified mutual inductance parameter estimation model can be obtained:
Figure FDA0004001943850000046
as can be seen from equation (18), if the above model is used to realize online estimation of mutual inductance parameters, high-frequency current of the receiving coil and the transmitting coil needs to be collected, but the system frequency operates at hundreds of khz, even at several mhz and tens of mhz, which increases the difficulty in identifying mutual inductance parameters and increases the hardware cost of the system;
in order to solve the problems, a fundamental wave analysis method of a circuit is introduced, and the fundamental wave analysis method can be known as follows:
Figure FDA0004001943850000051
in U i_RMS For the i-th phase inverter output voltage U i The effective value of the fundamental voltage of the (I) can be obtained at the same time i_RMS The method comprises the following steps:
Figure FDA0004001943850000052
according to the principle of series circuit voltage division, the effective value U of the input voltage of the port of the synchronous rectification circuit of the receiving side is obtained rec The method comprises the following steps:
Figure FDA0004001943850000053
according to fundamental wave analysis method, the relation between the effective value of the input voltage and the output DC voltage of the synchronous rectification circuit port is as follows:
Figure FDA0004001943850000054
the mutual inductance model algorithm can be obtained by the combined type (19) to the formula (22):
Figure FDA0004001943850000055
in formula (3), U i Output voltage amplitude for i-th phase inverter port, U bucki The voltage is outputted to the i-th phase pre-stage synchronous BUCK circuit.
8. The method for online evaluation of dynamic mutual inductance based on wireless power transmission system according to claim 4, wherein the fixed duty ratio is set to 70% when the multiphase synchronous BUCK circuit acquires each mutual inductance.
CN202211620682.7A 2022-12-15 2022-12-15 Dynamic mutual inductance online evaluation method based on wireless power transmission system Pending CN116054424A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116404874A (en) * 2023-06-05 2023-07-07 苏州萨沙迈半导体有限公司 Switching power supply converter and load transient detection circuit thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116404874A (en) * 2023-06-05 2023-07-07 苏州萨沙迈半导体有限公司 Switching power supply converter and load transient detection circuit thereof
CN116404874B (en) * 2023-06-05 2023-08-22 苏州萨沙迈半导体有限公司 Switching power supply converter and load transient detection circuit thereof

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