Maximum efficiency tracking control method and system for wireless power transmission systems

Abstract

This invention discloses a maximum efficiency tracking control method and system for a wireless power transmission system. By adjusting the phase shift angle θ2 of the semi-active rectifier and the phase shift angle θ1 of the high-frequency inverter, constant voltage output and maximum efficiency tracking are simultaneously achieved. θ1 and θ2 are continuously adjusted, and when they equal σ / M, it represents matching to the optimal load point. The implementation process of this invention is simple, computationally inefficient, and requires no complex circuits or matrices for related calculations. It improves the transmission efficiency of the wireless power transmission system while achieving constant voltage output.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a method and system for maximum efficiency tracking control of a wireless power transmission system. Background Technology

[0002] Wireless Power Transfer (WPT) systems are widely used in electric vehicles, implantable medical devices, and electronic equipment due to their flexibility, reliability, and safety. Efficiency is a crucial indicator for WPT systems, as it determines the future prospects of the technology. Maximum efficiency tracking (MET) is an effective method to improve efficiency. Its basic idea is to control the system so that the equivalent load resistance is always matched to the optimal value, allowing the WPT system to operate at maximum efficiency and thus improving overall system efficiency. In recent years, the use of DC-DC converters and pulse density modulation active rectifiers to achieve impedance matching in MET has improved transmission efficiency, but it cannot achieve constant voltage output. Furthermore, WPT systems are loosely coupled; when there is a misalignment between the transmitting and receiving coils, the mutual inductance and coupling coefficient change, directly affecting efficiency.

[0003] Traditional maximum efficiency tracking (WPT) methods mostly employ passive impedance networks or load modulation. Load modulation involves a DC-DC converter on the receiver side adjusting the output voltage, while the transmitter achieves WPT control by dynamically searching for the minimum input power to provide an approximately constant output power; this calculation process is complex. Passive impedance networks utilize complex and bulky matrices composed of inductors, capacitors, semiconductor switches, and corresponding drive circuits, which undoubtedly increases the size, cost, and control complexity of the WPT system. DC-DC converters also suffer from the same problem. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a maximum efficiency tracking control method and system for wireless power transmission systems, which eliminates the need for cumbersome calculations and reduces control complexity, in order to address the shortcomings of the existing technology.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a maximum efficiency tracking control method for a wireless power transmission system, wherein the wireless power transmission system includes a high-frequency inverter circuit, a resonant circuit, and a semi-active rectifier circuit connected in sequence; the resonant circuit includes a transmitting coil and a receiving coil coupled to the transmitting coil; the method includes the following steps:

[0006] S1. Determine the input DC voltage U of the wireless power transfer system. dc Set the initial phase shift angle θ of the high-frequency inverter circuit. 1(0)=π, adjust the phase shift angle θ2 of the receiving-side active rectifier to make the output DC voltage reach the preset constant voltage value U. B Record the phase shift angle θ at the current moment. 1(0) and θ 2(0) ;θ 2(0) This represents the phase shift angle of the receiving side active rectifier at the current moment, i.e., time 0.

[0007] S2. At time t, θ 1(t) =θ 1(t-1) -Δθ1, record the phase shift angle θ 2(t) ;θ 1(t) Let θ be the phase shift angle of the high-frequency inverter circuit at time t. 2(t) Let θ be the phase shift angle of the receiving side active rectifier at time t; Δθ1 is the adjustment amount of the phase shift angle of the high-frequency inverter circuit between two adjacent times; where t>1;

[0008] S3, Judgment Is it equal to If yes, then end; otherwise, increment the value of t by 1 and return to step S2; where Y = sinθ 1(t) / 2, X=sinθ 2(t) / 2; This represents the first derivative of Y at time t; This is the allowable error.

[0009] This invention eliminates the need for tedious calculations to evaluate the coupling coefficient in real time and avoids the need for expensive current sensors on the converter. It can be widely applied in electric vehicles, smartphones, and medical fields. By adjusting the phase shift angle θ2 of the semi-active rectifier and the phase shift angle θ1 of the high-frequency inverter, constant voltage output and maximum efficiency tracking are simultaneously achieved. Continuous adjustment of θ1 and θ2... σ / M represents matching to the optimal load point. The implementation of this invention is simple, computationally inexpensive, requires no complex circuits, and eliminates the need for complex matrices for related calculations. It improves the transmission efficiency of wireless power transmission systems while achieving constant voltage output.

[0010] In this invention, when the wireless power transmission system reaches its maximum transmission efficiency, Where M is the mutual inductance of the transmitting and receiving coils resonating, and σ = U B L1 / U dc L1 is the compensating inductance of the transmitting coil, and M is related to the maximum transmission efficiency η of the wireless power transmission system. max The relationship between them is:

[0011]

[0012] Among them, R Pω is the parasitic resistance of the transmitting coil, and ω is the angular frequency of the line power transmission system.

[0013] In this invention, the relationship between the phase shift angle θ1 of the high-frequency inverter circuit and the phase shift angle θ2 of the receiving-side active rectifier is as follows: R S L1 is the parasitic resistance of the receiving coil, L2 is the compensating inductance of the transmitting coil, and R is the inductance of the transmitting coil. B It is a battery charging resistor in a semi-active rectifier circuit.

[0014] In this invention, the first derivative of Y at any given time...

[0015] In this invention, when the output DC voltage reaches a preset constant voltage value U B At that time, the voltage gain G of the wireless power transfer system UU for: in, U1 is the output voltage of the high-frequency inverter circuit, L1 is the compensating inductance of the transmitting coil, and M is the mutual inductance of the transmitting and receiving coils.

[0016] The output voltage U1 of the high-frequency inverter circuit of this invention is: θ1 is the phase shift angle of the high-frequency inverter circuit.

[0017] As an inventive concept, the present invention also provides a maximum efficiency tracking control system for a wireless power transmission system, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the above-described maximum efficiency tracking control method for a wireless power transmission system of the present invention.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention does not require cumbersome calculations to evaluate the coupling coefficient in real time, nor does it require expensive current sensors on the converter, and can be widely used in electric vehicles, smartphones, medical fields and other fields; the method of the present invention has a simple calculation process, and achieves constant voltage output of the wireless power transmission system while realizing maximum efficiency tracking of the wireless power transmission system. Attached Figure Description

[0019] Figure 1 This is a structural diagram of the LCC-S compensation topology WPT system according to an embodiment of the present invention;

[0020] Figure 2 This is a circuit diagram of the equivalent circuit structure of the LCC-S compensation topology in an embodiment of the present invention;

[0021] Figure 3 This is a control block diagram of a wireless power transmission system according to an embodiment of the present invention;

[0022] Figure 4This is a flowchart of the maximum efficiency tracking control method according to an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In this document, the terms "first," "second," and other similar words are not intended to imply any order, quantity, or importance, but are merely used to distinguish different elements. The terms "one," "a," and other similar words are not intended to indicate the existence of only one of the stated things, but rather that the description pertains to only one of the two stated things, which may include one or more. The terms "comprising," "including," and other similar words are intended to indicate a logical relationship, not a spatial relationship. For example, "A includes B" means that logically B belongs to A, not that spatially B is located inside A. Furthermore, the meanings of the terms "comprising," "including," and other similar words should be considered open-ended, not closed. For example, "A includes B" means that B belongs to A, but B does not necessarily constitute all of A; A may also include other elements such as C, D, and E.

[0025] Figure 1 This is a structural diagram of a wireless power transfer system according to an embodiment of the present invention. Based on an LCC-S topology magnetically coupled wireless power transfer system with a semi-active rectifier, the entire system includes a high-frequency inverter circuit, a resonant circuit, and a rectifier output circuit (semi-active rectifier circuit). After the LCC-S resonant topology, energy flows from the primary coil to the secondary coil via magnetic coupling. The wireless power transfer system outputs energy through the rectifier output circuit. dc It is a DC voltage source used to drive the primary-side high-frequency bridge inverter circuit to generate a high-frequency square wave voltage. S1-S4 and S... A -S B These are the switching transistors for the transmitter-side inverter and the receiver-side semi-active rectifier, respectively. L1, C1, C P These are the primary-side compensation inductor, parallel capacitor, and series compensation capacitor. L P and L S These are the equivalent inductances on the transmitting and receiving sides, respectively. R P and R S These are the parasitic resistances of the transmitting and receiving coils, respectively. C S It is a secondary-side compensation capacitor.

[0026] Figure 2 This is the LCC-S equivalent circuit model. For ease of analysis, a fundamental frequency approximation is used, so only the fundamental frequency component is considered.

[0027]

[0028] U1 is the output voltage of the high-frequency inverter circuit, and θ1 is the phase shift angle of the high-frequency inverter circuit. θ2 is the phase shift angle of the receiving-side active rectifier. Similarly, for the receiving-side rectifier circuit:

[0029]

[0030] Write Kirchhoff's voltage equations (KVL) on both the transmitting and receiving sides:

[0031]

[0032] Among them, I1 and I P I represents the root mean square value of the current phasor in the transmitting and receiving circuits, respectively. o These are the effective values ​​of the load current. Equivalent impedances Z1 = jωL1, Z2 = 1 / jωC1, Z3 = jωL P +1 / jωC P Z4 = jωM, Z5 = jωL S +1 / jωC S When the L on the transmitter and receiver P (L S ) and C P (C S When fully compensated, this means Z1 + Z2 = 0 and Z5 = 0. If Z2 + Z3 = 0 is also satisfied, then the system input impedance Z in This can be deduced as:

[0033]

[0034] This embodiment designs a control optimization scheme based on constant voltage output, achieving constant voltage output by designing the system to operate in constant voltage mode. The frequency is the system operating frequency, and the voltage gain in constant voltage mode is:

[0035]

[0036] Among them G UU It's the voltage gain. You can see the output voltage magnitude U. O and voltage gain G UU It is constant, and a constant voltage output can be achieved. Therefore, the output voltage and voltage gain can be simplified to:

[0037]

[0038] As can be seen from the above formula, the voltage gain is only related to the mutual inductance and the self-inductance. When the mutual inductance remains unchanged, the voltage gain is a constant.

[0039] This embodiment designs a maximum efficiency tracking strategy based on LCC-S, and its input and output powers can be derived as follows:

[0040]

[0041] Where P2 is the output power, P1 is the input power, and ω is the system angular frequency. The system efficiency η can be obtained from the input and output power calculation formulas:

[0042]

[0043] It is clear from the formula for calculating system efficiency η that system efficiency is affected by mutual inductance M and load resistance R. O The effect of η. The first derivative of η with respect to M is greater than Therefore, system efficiency increases with increasing mutual inductance. Furthermore, η versus R O The first and second derivatives can be calculated as follows:

[0044]

[0045] Let the above expression equal 0, R O (max) can be derived as (R) P =R S ):

[0046]

[0047] where R O(max) To achieve the optimal load for maximum efficiency.

[0048]

[0049] With R O The increase, Initially positive, then negative, efficiency first increases and then decreases with increasing load resistance. When R... P Much smaller than R O At that time, R P 2 R O 3 Very small, then The calculation result is always negative. This means Point R with maximum value O(MAX) To maximize system efficiency. Due to the parasitic resistance R of the coil P and R S Very small, R O(max)It can be approximated as ωM by the formula above. When the coil deflects, M will change, therefore R... O(MAX) Also according to the formula Change.

[0050] Variations in mutual inductance and load resistance maintain a constant voltage output by automatically adjusting the phase shift angle θ2 of the semi-active rectifier. However, without transmitter control, variations in system output power cause the input power to deviate from its optimal value, reducing system transmission efficiency. The system efficiency is maximized by matching the optimal load point using the phase shift angle θ1 of the high-frequency inverter circuit. By adjusting θ1, different θ2 values ​​can be obtained; an optimal matching point exists between θ1 and θ2 that maximizes system efficiency. If there is no power loss at the receiving side, we can obtain:

[0051]

[0052] Formula and Substitute into the formula U1 can be transformed into:

[0053]

[0054] Where Y = sinθ1 / 2, X = sinθ2 / 2. Substitution The relationship between θ1 and θ2 can be obtained as follows:

[0055]

[0056] from It can be seen that θ1 and θ2 have a coupled interaction. Finding the functional relationship between θ1 and θ2 corresponding to the optimal equivalent load point allows for maximum efficiency tracking. Taking the derivative with respect to Y:

[0057]

[0058] Adjusting θ1 and θ2 to keep the corresponding function at the optimal load point achieves maximum efficiency tracking. (Combined with the formula...) and We can obtain:

[0059]

[0060] X 2 (max) represents X under optimal load. 2 .

[0061] definition for U B L1 / U dc For σ, we can further obtain:

[0062]

[0063] Formula Substitution Get η max :

[0064]

[0065] When the system transmission efficiency reaches its maximum value This holds true. Even if coil deviation causes changes in mutual inductance, as long as the point on the derivative mutual inductance curve... Corresponding to the optimal equivalent load point, maximum efficiency tracking can be achieved. When the coil remains stationary and the mutual inductance remains unchanged, It is a constant.

[0066] like Figure 3 and Figure 4 As shown, the steps of the maximum efficiency tracking integrated control method for the wireless power transmission system in this embodiment are as follows:

[0067] S1. Determine the input DC voltage U of the wireless power transfer system. dc Set the initial phase shift angle θ of the high-frequency inverter circuit. 1(0) =π, adjust the phase shift angle θ2 of the receiving-side active rectifier to make the output DC voltage reach the preset constant voltage value U. B Record the phase shift angle θ at the current moment. 1(0) and θ 2(0) ;θ 2(0) This represents the phase shift angle of the receiving side active rectifier at the current moment, i.e., time 0.

[0068] S2. At time t, θ 1(t) =θ 1(t-1) -Δθ1, record the phase shift angle θ 2(t) ;θ 1(t) Let θ be the phase shift angle of the high-frequency inverter circuit at time t. 2(t) Let θ be the phase shift angle of the receiving side active rectifier at time t; Δθ1 is the adjustment amount of the phase shift angle of the high-frequency inverter circuit between two adjacent times; where t>1;

[0069] S3, Judgment Is it equal to If yes, then the process ends; otherwise, increment the value of t by 1, increasing the adjustment amount of the phase shift angle of the high-frequency inverter circuit at the two adjacent moments, and return to step S2; where Y = sinθ 1(t) / 2, X=sinθ 2(t) / 2; This represents the first derivative of Y at time t; This is the allowable error.

[0070] In step S3 above, if equal This indicates that the wireless power transfer system is in θ 1(t-1) and θ 2(t-2) Maximum efficiency tracking control is achieved at this point. If it fails, it indicates that the wireless power transfer system has not reached its optimal load point. Continue to slightly increase the phase shift angle θ1 of the high-frequency inverter circuit to search for the maximum efficiency point. Repeat step S3 to further adjust θ. 1(m+1) =θ 1(m) -Δθ1, and record θ 2(m+1) Until the equation Then at θ 1(m) and θ 2(m) Maximum efficiency tracking is achieved at this point. Where 1 ≤ m ≤ t.

[0071] In this embodiment, Δθ1 can be set to a small value, such as π / 180.

[0072] Example 2

[0073] Embodiment 2 of the present invention provides a maximum power point tracking integrated control system corresponding to the wireless power transmission system of Embodiment 1 above, including a memory, a processor and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method of Embodiment 1 above.

[0074] In some implementations, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0075] In other implementations, the processor can be any type of general-purpose processor, such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation here.

[0076] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented in various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0077] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0078] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0079] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0080] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A maximum efficiency tracking control method for a wireless power transmission system, the wireless power transmission system comprising a high-frequency inverter circuit, a resonant circuit, and a semi-active rectifier circuit connected in sequence; the resonant circuit comprising a transmitting coil and a receiving coil coupled to the transmitting coil; characterized in that, The method includes the following steps: S1. Determine the input DC voltage U of the wireless power transfer system. dc Set the initial phase shift angle θ of the high-frequency inverter circuit. 1(0) =π, adjust the phase shift angle θ2 of the receiving-side active rectifier to make the output DC voltage reach the preset constant voltage value U. B Record the phase shift angle θ at the current moment. 1(0) and θ 2(0) ;θ 2(0) This represents the phase shift angle of the receiving side active rectifier at the current moment, i.e., time 0. S2. At time t, θ 1(t) =θ 1(t-1) -Δθ1, record the phase shift angle θ 2(t) ;θ 1(t) Let θ be the phase shift angle of the high-frequency inverter circuit at time t. 2(t) Let θ be the phase shift angle of the receiving side active rectifier at time t; Δθ1 is the adjustment amount of the phase shift angle of the high-frequency inverter circuit between two adjacent times; where t>1; S3, Judgment Is it equal to If yes, then end; otherwise, increment the value of t by 1 and return to step S2; where Y = sinθ 1(t) / 2, X=sinθ 2(t) / 2; This represents the first derivative of Y at time t; This is the allowable error; Where M is the mutual inductance of the transmitting and receiving coils resonating, and σ = U B L1 / U dc L1 is the compensating inductance of the transmitting coil, and M is related to the maximum transmission efficiency η of the wireless power transmission system. max The relationship between them is: Among them, R P ω is the parasitic resistance of the transmitting coil, and ω is the angular frequency of the line power transmission system; When the output DC voltage reaches the preset constant voltage value U B At that time, the voltage gain G of the wireless power transfer system UU for: in, U1 is the output voltage of the high-frequency inverter circuit, L1 is the compensating inductance of the transmitting coil, and M is the mutual inductance of the transmitting and receiving coils.

2. The maximum efficiency tracking control method for a wireless power transmission system according to claim 1, characterized in that, The relationship between the phase shift angle θ1 of the high-frequency inverter circuit and the phase shift angle θ2 of the receiver-side active rectifier is as follows: R S L1 is the parasitic resistance of the receiving coil, L2 is the compensating inductance of the transmitting coil, and R is the inductance of the transmitting coil. B It is a battery charging resistor in a semi-active rectifier circuit.

3. The maximum efficiency tracking control method for a wireless power transmission system according to claim 2, characterized in that, The first derivative of Y at any given time 4. The maximum efficiency tracking control method for a wireless power transmission system according to claim 1, characterized in that, The output voltage U1 of the high-frequency inverter circuit is: θ1 is the phase shift angle of the high-frequency inverter circuit.

5. A maximum efficiency tracking and control system for a wireless power transmission system, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 4.

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