Nonlinear wireless power transmission system and method with variable coupling coefficient stability

Abstract

The present invention discloses a wireless power transmission method and device with variable coupling coefficient stability. The method and device include a primary-side rectifier and filter unit, a primary-side high-frequency inverter, a primary-side DC / DC unit, a primary-side linear topology structure, a primary-side transmitting coil, a secondary-side receiving coil, a secondary-side shunt capacitor, a secondary-side variable inductor or capacitor structure, and a secondary-side rectifier and filter unit. The secondary-side variable inductor or capacitor structure includes at least one linear inductor L2 or linear capacitor C3 operating in a switching state. The output voltage waveform of the present invention is between a sine wave and a square wave, and can achieve automatic voltage stabilization and spectrum spread under variable coupling coefficient conditions without the involvement of active control devices. The stability of this system does not rely on communication feedback, has high reliability, and is low in cost. It can maintain high efficiency and stability of wireless power transmission when the coupling coefficient changes.

Description

Technical Field

[0001] The present invention belongs to wireless power transmission technology in the field of electrical engineering, and specifically relates to a magnetic-field coupled power transmission device. This method utilizes natural or artificial variable inductance or nonlinear resonance of inductance to improve traditional wireless power transmission systems, thereby increasing the system's transmission distance and transmission stability. Specifically disclosed are a nonlinear wireless power transmission system with variable coupling coefficient stability and a method for implementing the system. Background Art

[0002] In recent years, driven by social development needs and technological advancements, wireless power transmission technology has experienced rapid development. Magnetic field-coupled wireless power transmission, with its advantages of high transmission power, high efficiency, and excellent safety, is expected to find widespread commercial application in electric vehicles, industrial robots, mobile phone charging, and other fields.

[0003] The development of wireless power transmission technology dates back 100 years. At that time, Nikola Tesla proposed a high-power wireless power transmission technology based on a spark gap. However, for various reasons, his technical solution and method have not been replicated to this day.

[0004] To improve the performance of wireless power transmission, researchers have attempted to introduce various compensating topologies and control methods to overcome the low coupling coefficient and high leakage inductance characteristics of wireless power transmission systems, thereby increasing their transmission distance and improving transmission efficiency. In 2009, Ragif E. Hamam et al. at the Massachusetts Institute of Technology, drawing on the electromagnetically induced transparency (EIT) effect in quantum mechanics, proposed the concept of a relay coil, significantly improving energy conversion efficiency and distance. In 2011, Mitsubishi Electric Research Institute of Cambridge applied electromagnetic metamaterials to wireless power transmission. Using a SRR ring structure similar to that used in electromagnetic metamaterials, they significantly increased the distance and efficiency of wireless power transmission. Other researchers have also improved basic topologies, proposing LCC and LLC topologies, aiming to achieve constant current and constant voltage output performance, and have applied these to wireless power transmission in electric vehicles.

[0005] However, traditional research methods have not broken through the limitations of linear resonance, resulting in poor system stability, or overly complex control circuits and high costs, making it impossible to smoothly move from the laboratory to the industrial field. In order to solve the stability problem of wireless power transmission systems under variable coupling coefficient conditions, some new methods have emerged in recent years. Zhao Lei from the University of Auckland in New Zealand used a hybrid topology to achieve constant power transmission within a certain range of space; Zhang Bo's research group at South China University of Technology used a fractional-order method to achieve constant power output under variable coupling coefficient conditions. In essence, these methods break through the traditional communication-based feedback control, implement energy-based control methods, and achieve good results.

[0006] This invention proposes a high-power, nonlinear resonant wireless power transmission system based on inductance or capacitance control. Unlike traditional linear resonant modes, this system achieves variable coupling coefficient stability at higher operating frequencies (10 kHz-300 kHz), while also being low-cost and easily applicable to industrial applications. The invention's air gap structure promises to replicate Tesla's original design. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for realizing nonlinear resonance by utilizing variable inductance or variable capacitance, thereby improving the performance limitations of conventional wireless power transmission systems and enhancing the output voltage stability under conditions of variable coupling coefficients.

[0008] The object of the present invention is achieved in this way. The present invention provides a wireless power transmission system based on variable inductance, including a primary side and a secondary side, wherein the primary side includes a primary side AC power supply, a primary side rectifier and filter unit, a primary side DC / DC Unit, primary side high frequency inverter, primary side LCC linear topology structure (other linear topologies may also be used) and primary side transmitting coil; the secondary side includes a secondary side receiving coil, a secondary side shunt capacitor, a secondary side variable inductance structure, a secondary side rectifier and filter unit and a load electrically connected in sequence; the secondary side receiving coil receives the electromagnetic field emitted by the primary side transmitting coil through the mutual inductance M and converts it into electrical energy; the secondary side includes a secondary side receiving coil, a secondary side shunt capacitor and a secondary side rectifier and filter unit electrically connected in sequence; the secondary side receiving coil receives the electromagnetic field emitted by the primary side transmitting coil through the mutual inductance M and converts it into electrical energy; a nonlinear device connected in parallel with the shunt capacitor is further provided between the secondary side shunt capacitor and the secondary side rectifier and filter unit, and the nonlinear device converts the inductance or capacitance value coupled with the secondary side shunt capacitor based on the voltage across the secondary side receiving coil as a judgment condition.

[0009] The nonlinear device uses a magnetic saturation transformer with a magnetic leakage structure to achieve switch switching, and the magnetic core of the magnetic saturation transformer works alternately in the linear region and the saturation region of the BH characteristic curve.

[0010] The nonlinear device may also be a secondary-side variable inductance structure or a secondary-side variable capacitance structure, wherein the secondary-side variable inductance structure includes: at least one variable inductor that alternately operates at different inductances. The implementation method may be the natural characteristics of the magnetic core material or the circuit switching of a linear inductor; the secondary-side parallel capacitor may form a nonlinear resonance with the variable inductance or capacitance structure, wherein the resonant waveform is between a sine wave and a square wave, and the capacitance value is selected differently from the linear resonance. When the total capacitance C of all the secondary-side parallel capacitors forms a nonlinear resonance with the total inductance L of all the secondary-side inductors, the following conditions must be met: 1. <LCω 2 0<2.

[0011] The purpose of the present invention can also be achieved in this way: when the primary side remains unchanged, the secondary side includes a secondary side receiving coil, a secondary side parallel capacitor, a secondary side variable capacitor structure, a secondary side rectifier filter unit and a load that are electrically connected in sequence; the secondary side receiving coil receives the electromagnetic field emitted by the primary side transmitting coil through the mutual inductance M and converts it into electrical energy; the secondary side variable capacitor structure includes: at least one variable capacitor that alternately works at different capacitances. The implementation method is the circuit switching of the linear capacitor; the secondary side variable capacitor can form a nonlinear resonance with the secondary side receiving coil, and the resonant waveform is between a sine wave and a square wave;

[0012] Preferably, the secondary-side variable inductor structure adopts the following circuit structure: including at least one controllable inductor L2 and a constant-voltage on-off switch K2. Based on the frequency and nonlinear resonance conditions, when the voltage across K2 is greater than a set value, the switch is turned on; when it is less than the set value, the switch is turned off. The constant-voltage switch can be a passive structure such as a spark gap (the discharge voltage can be adjusted by the gap) or a ceramic discharge tube; the constant-voltage switch can also be an active structure such as a MOS tube based on voltage detection.

[0013] Preferably, the secondary side variable inductance structure can also utilize the saturation characteristics of the magnetic material, that is, the magnetic core alternately operates in the linear region and the saturation region of the BH characteristic curve;

[0014] Preferably, the secondary side variable inductance structure can use a magnetic saturation transformer with a leakage magnetic structure; one of ferrite and nano-amorphous alloy magnetic materials can be used as the material of the leakage magnetic structure, the leakage magnetic air gap is between 0.2mm and 1mm, the operating frequency is between 10KHz and 300KHz, and the inductance of the input coil is more than 3 times the inductance of the secondary side receiving coil (250).

[0015] Preferably, the secondary-side variable capacitance structure adopts the following circuit structure: including at least one controllable capacitor C3 and a constant-voltage on-off switch K2. Based on the frequency and nonlinear resonance conditions, the switch switches when the voltage across K2 exceeds a set value. The constant-voltage switch can be an active structure such as a MOS transistor based on voltage detection.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. Without any communication or feedback links, this system achieves a constant output voltage under variable coupling coefficient conditions. In other words, the system output voltage is independent of distance.

[0018] 2. The configuration of the leakage transformer on the secondary side eliminates the traditional secondary side DC / DC voltage regulation link and simplifies the system structure.

[0019] 3. The resonant characteristics of this topology are not limited by the traditional LC resonance curve and can resonate within a wide frequency band, avoiding system performance degradation caused by operating temperature and component errors. It is particularly suitable for wireless power transmission applications that require operation in harsh environments, such as electric vehicles and high-speed railways.

[0020] 4. The high stability of this system is derived from the adaptive characteristics of nonlinear devices. No active active devices are required for control intervention, which greatly improves the system response speed. It is particularly suitable for electric vehicles, high-speed railways and other equipment that require high-speed mobile wireless power transmission.

[0021] 5. The nonlinear resonance of the variable inductor and variable capacitor has a negative resistance effect, with two stable operating points. Under appropriate conditions, the negative resistance effect can offset system losses, theoretically improving the system quality factor Q and coil ESR loss, and improving the squareness ratio of the system's amplitude-frequency characteristics, thereby extending transmission distance and increasing efficiency.

[0022] 6. The optimal spark gap structure is expected to replicate Tesla's resonant amplifier design from 100 years ago.

[0023] In summary, the present invention can theoretically break through the performance limitations of traditional wireless power transmission systems, and has a simple structure, reliable performance, and is easy to commercially apply. It is an important technical and method innovation in this field. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the overall block diagram of the variable inductance solution system of the present invention.

[0025] Figure 2 It is a variable inductance nonlinear resonance scheme based on the voltage-controlled switch K2 structure.

[0026] Figure 3It is the structural diagram of the voltage-controlled switch K2 based on active devices.

[0027] Figure 4 It is a variable inductance nonlinear resonance scheme based on high-frequency leakage transformer.

[0028] Figure 5 This is a diagram of the variable inductance structure of an asymmetric high-frequency leakage transformer.

[0029] Figure 6 This is a diagram of the variable inductance structure of a symmetrical high-frequency leakage transformer.

[0030] Figure 7 This is the overall block diagram of the variable capacitance solution system of the present invention.

[0031] Figure 8 It is a variable capacitor nonlinear resonance scheme based on the voltage-controlled switch K2 structure. DETAILED DESCRIPTION

[0032] The following is a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. It is obvious that the embodiments described are only part of the embodiments of the present invention. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without making any creative efforts are within the scope of protection of this patent.

[0033] Figure 1 This is the overall block diagram of the variable inductance solution system of the present invention. Figure 1 It can be seen that the present invention proposes a wireless power transmission system based on secondary-side variable inductance nonlinear resonance, including a primary side 100 and a secondary side 200, wherein the primary side 100 includes a primary-side AC power supply 160, a primary-side rectifier and filter unit 110, a primary-side DC / DC unit 120, a primary-side high-frequency inverter 130, a primary-side linear topology structure 140, and a primary-side transmitting coil 150 electrically connected in sequence; the secondary side 200 includes a secondary-side receiving coil 250, a secondary-side shunt capacitor 210, a secondary-side variable inductance structure 220a, a secondary-side rectifier and filter unit 230, and a load 240 electrically connected in sequence; the secondary-side receiving coil 250 receives the electromagnetic field emitted by the primary-side transmitting coil 150 through the mutual inductance M and converts it into electrical energy.

[0034] In an embodiment of the present invention, the secondary-side variable inductance structure 220a includes the following three circuit structures:

[0035] The first type is a variable inductor consisting of a linear inductor L2 and a voltage-controlled switch K2. The linear inductor L2 is connected in series with the switch K2 and is connected in parallel with the secondary side receiving coil 250 and the secondary side rectifier filter unit 230. Figure 2 .

[0036] In an embodiment of the present invention, the voltage-controlled switch K2 includes the following structure:

[0037] 1. Spark Gap Structure. This is the structure Tesla used to generate high-frequency signals. The gap can be air or an inert gas.

[0038] 2. Devices with voltage-limiting conduction function such as ceramic discharge tubes or semiconductor discharge tubes.

[0039] 3. Use the rectifier diode D1 and capacitor C to detect the voltage across the secondary side receiving coil, and use a voltage comparator to compare. When it exceeds a certain value, it drives the MOS tube and other active devices to close, completing the switching function of K2. Figure 3 .

[0040] The second type: The variable inductor is composed of a high-frequency leakage transformer L2 with saturation characteristics. The high-frequency capacitor C2 and the high-frequency leakage transformer L2 are connected in parallel and then connected in series with the secondary side receiving coil 250. The secondary output of the high-frequency leakage transformer L2 is wound and transformed and then connected in parallel with the rectifier filter unit 230. For the specific structure, see Figure 4 .

[0041] In an embodiment of the present invention, the high-frequency magnetic leakage transformer may include the following structure:

[0042] 1. Asymmetric E-type structure. Figure 5 An air gap is left on one side of the E-type transformer, while no air gap is left on the other side, so that the right side of the high-frequency transformer works alternately in saturation and cutoff states, realizing variable inductance.

[0043] 2. Symmetrical magnetic leakage structure.

[0044] A ferrite or nano-amorphous alloy magnetic material can be used as the magnetic leakage structure, the magnetic leakage air gap is between 0.2mm and 1mm, the operating frequency is between 10KHz and 300KHz, and the inductance of the input coil is more than 3 times the inductance of the secondary side receiving coil (250).

[0045] like Figure 6 shown. Figure 77 shows the overall block diagram of the variable capacitor scheme system of the present invention. As can be seen from FIG7 , the wireless power transmission system based on the nonlinear resonance of the secondary variable capacitor proposed by the present invention includes a primary side 100 and a secondary side 200. The primary side 100 includes a primary side AC power supply 160, a primary side rectifier and filter unit 110, a primary side DC / DC unit 120, a primary side high-frequency inverter 130, a primary side linear topology structure 140, and a primary side transmitting coil 150, which are electrically connected in sequence. The secondary side 200 includes a secondary side receiving coil 250, a secondary side shunt capacitor 210, a secondary side variable capacitor structure 220b, a secondary side rectifier and filter unit 230, and a load 240, which are electrically connected in sequence. The secondary side receiving coil 250 receives the electromagnetic field emitted by the primary side transmitting coil 150 through the mutual inductance M and converts it into electrical energy.

[0046] In an embodiment of the present invention, the secondary-side variable capacitance structure 220b includes the following circuit structure:

[0047] The variable capacitor is composed of a linear capacitor C3 and a voltage-controlled switch K2. The linear capacitor C3 is connected in series with the switch K2 and is connected in parallel with the secondary side receiving coil 250 and the secondary side rectifier filter unit 230. The implementation of the voltage-controlled switch also includes three implementation methods as described above. For the specific structure, see Figure 8 In the embodiment of the present invention, the secondary side variable capacitance structure can use either a passive structure such as a spark gap or a ceramic discharge tube, or an active switch structure, as follows:

[0048] The voltage across the secondary receiving coil is detected using a rectifier diode D1 and capacitor C. A voltage comparator is used for comparison. When the voltage exceeds a certain value, the MOS tube and other active devices are driven to disconnect, completing the switching function of K2. That is, the nonlinear resonant frequency conversion is completed by switching the linear capacitor C3. See the circuit diagram. Figure 3 .

[0049] Embodiments of the present invention provide a wireless power transmission system based on nonlinear resonance of variable capacitors or variable inductors. Compared to existing technologies, this solution eliminates the need for any communication or feedback loops. This system achieves a constant output voltage under variable coupling coefficient conditions, meaning the system output voltage is independent of distance. Furthermore, the configuration of a leakage transformer on the secondary side of this system eliminates the traditional DC / DC voltage regulation step, simplifying the system structure. Furthermore, the resonant characteristics of this topology are not limited by the traditional LC resonance curve and can resonate over a wide frequency band, avoiding system performance degradation caused by operating temperature and component errors. This system is particularly suitable for wireless power transmission applications requiring operation in harsh environments, such as electric vehicles and high-speed rail. The system's high stability stems from the adaptive properties of the nonlinear devices, eliminating the need for active control intervention, significantly improving system response speed and making it particularly suitable for applications requiring high-speed mobile wireless power transmission, such as electric vehicles and high-speed rail. The nonlinear resonance of the variable inductor and variable capacitor exhibits a negative resistance effect, resulting in two stable operating points. Under appropriate conditions, this negative resistance effect can offset system losses, theoretically increasing the system quality factor (Q) and coil ESR losses, and improving the squareness ratio of the system's amplitude-frequency characteristics, thereby extending transmission distance and increasing efficiency. .

Claims

1. A nonlinear wireless power transmission system with variable coupling coefficient stability, comprising a primary side (100) for converting wired current into electromagnetic waves, and at least one secondary side cooperating with a transmitting end for receiving electromagnetic waves from the transmitting end and converting them into wired current; the secondary side (200) comprises a secondary side receiving coil (250), a secondary side shunt capacitor (210), and a secondary side rectifier filter unit (230) electrically connected in sequence; the secondary side receiving coil (250) receives the electromagnetic field emitted by the primary side transmitting coil (150) through a mutual inductance M and converts it into electrical energy, characterized in that A nonlinear device connected in parallel with the secondary-side parallel capacitor (210) is further provided between the secondary-side parallel capacitor (210) and the secondary-side rectifier filter unit (230), the nonlinear device transforming the inductance or capacitance value coupled with the secondary-side parallel capacitor (210) based on the voltage across the secondary-side receiving coil as a judgment condition, the nonlinear device using a magnetic saturation transformer with a magnetic leakage structure to achieve switch switching, the magnetic core of the magnetic saturation transformer alternately working in the linear region and the saturation region of the BH characteristic curve, the nonlinear device A secondary side variable inductance structure or a secondary side variable capacitance structure is provided, wherein the secondary side variable inductance or capacitance structure includes at least one variable inductor or capacitor that alternately works at different inductances or capacitances, the secondary side receiving coil (250), the secondary side parallel capacitor (210) and the secondary side variable inductance or capacitance structure form a nonlinear resonance, and the resonance waveform is between a sine wave and a square wave, wherein the total capacitance C of all the secondary side parallel capacitors and the total inductance L of all the secondary side inductors form a nonlinear resonance, and the conditions that need to be met at this time are: 1< LCω 0 2 <2.

2. The nonlinear wireless power transmission system with variable coupling coefficient stability according to claim 1, characterized in that: The secondary side variable inductance structure (220a) comprises a linear inductor L2 and a voltage-controlled switch K2, wherein the linear inductor L2 is connected in series with the voltage-controlled switch K2 and is connected in parallel with the secondary side receiving coil (250), the secondary side parallel capacitor (210) and the secondary side rectifier filter unit (230).

3. The nonlinear wireless power transmission system with variable coupling coefficient stability according to claim 1, characterized in that: The secondary side variable capacitance structure (220b) comprises a linear capacitor C3 and a voltage-controlled switch K2, wherein the linear capacitor C3 is connected in series with the voltage-controlled switch K2 and is connected in parallel with the secondary side receiving coil (250), the secondary side parallel capacitor (210) and the secondary side rectifying and filtering unit (230).

4. The nonlinear wireless power transmission system with variable coupling coefficient stability according to claim 2 or 3, characterized in that: The voltage-controlled switch is a spark gap switch, a ceramic discharge tube with voltage-limited conduction, or a semiconductor discharge tube with voltage-limited conduction; or the voltage across the secondary receiving coil is detected by a rectifier diode D1 and a capacitor C, and a voltage comparator is used for comparison. When the voltage exceeds a certain value, an active device such as a MOS tube is driven to close, completing the switching function of K2.

5. A method for nonlinear wireless power transmission with variable coupling coefficient stability, comprising a primary side (100) for converting wired current into electromagnetic waves, and at least one secondary side cooperating with a transmitting end for receiving electromagnetic waves from the transmitting end and converting them into wired current; the secondary side (200) comprises a secondary side receiving coil (250), a secondary side parallel capacitor (210), and a secondary side rectifier filter unit (230) electrically connected in sequence; the secondary side receiving coil (250) receives the electromagnetic field emitted by the primary side transmitting coil (150) through a mutual inductance M and converts it into electrical energy, characterized in that A nonlinear device connected in parallel with the shunt capacitor (210) is further provided between the secondary side shunt capacitor (210) and the secondary side rectifier filter unit (230). The nonlinear device is based on the voltage across the secondary side receiving coil as a judgment condition, and switches the capacitance value or inductance value in the system. The secondary side variable inductor or capacitor structure uses a magnetic saturation transformer with a leakage magnetic structure. The magnetic core of the magnetic saturation transformer alternately works in the linear region and the saturation region of the BH characteristic curve. The variable coupling device is a secondary side variable inductor structure or a secondary side variable capacitor structure. The secondary side variable inductor or capacitor structure includes at least one variable inductor or capacitor that alternately works in different inductances or capacitances. The secondary side receiving coil (250), the secondary side shunt capacitor (210) and the secondary side variable inductor or capacitor structure form a nonlinear resonance. The resonance waveform is between a sine wave and a square wave. The total capacitance C of all the secondary side shunt capacitors and the total inductance L of all the secondary side inductors form a nonlinear resonance. The conditions that need to be met at this time are: 1< LCω 0 2 <2.

6. The method for nonlinear wireless power transmission with variable coupling coefficient stability according to claim 5, characterized in that: The secondary side variable inductor can use one of ferrite and nano-amorphous alloy magnetic materials as a leakage magnetic structure, its leakage magnetic air gap is between 0.2mm and 1mm, its operating frequency is between 10KHz and 300KHz, and the inductance of its input coil is more than 3 times the inductance of the secondary side receiving coil (250).

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