Compact wireless power transmission system based on receiving side independent voltage control

Abstract

The invention provides a compact wireless electric energy transmission system based on receiving side independent voltage control. The compact wireless electric energy transmission system comprises coupling mechanism design and a receiving side PWM control method. A transmitting coil and a receiving coil of the coupling mechanism are formed by winding multilayer and multi-turn solenoid coils; a groove type ferrite magnetic core is arranged on the inner side of the coil and used for forming a magnetic shielding space so that an inverter or a rectifier can be arranged. Furthermore, by combining a solenoid structure, a reverse winding and a groove type magnetic core, a compact coupling mechanism with strong anti-offset performance is provided, and mutual inductance fluctuation in an offset range can be effectively reduced. The receiving side active rectifier adopts a PWM control method, odd symmetry three-level voltage is generated by adjusting the duty ratio, and wide-range output voltage independent regulation and control are achieved. According to the invention, high power density, high integration and strong anti-offset performance can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless charging, and in particular relates to a compact wireless power transmission system based on independent voltage control at a receiving side. Background Art

[0002] Wireless Power Transfer (WPT) technology achieves the transmission of electric energy in a contactless manner. It is widely used due to its safety, convenience and reliability, especially in the fields of consumer electronics, mobile devices and electric vehicles. It has significant market potential. In recent years, high-power density WPT systems have gradually become a research hotspot. Higher power density can achieve a compact design of the system structure and facilitate integration with electrical equipment. However, due to the compact size of high-power density systems, there are problems such as weak anti-deviance performance and difficulty in power regulation.

[0003] In terms of improving the performance of high-density WPT systems, the main approach is to use coil structures such as DD, BP, and overlap, or to add auxiliary anti-offset coils. However, the complex design of multiple coils often conflicts with the goal of high-density compact design. In addition, the traditional coil design does not fully consider the layout optimization of the primary and secondary converters, resulting in low system integration and a large overall volume. For output voltage regulation, existing technologies usually use reconfigurable topologies, adjustable compensation elements, or increase DC-DC conversion stages for control, but these methods will introduce additional inductors, increase system complexity and cost, and are not conducive to achieving efficient and compact design goals.

[0004] Output voltage regulation can also be achieved by controlling the switching logic of the active rectifier, but there are certain limitations. For example, through active rectifier phase shift modulation (Pulse Density Modulation, PSM), the output voltage can be accurately adjusted without communication, but the phase shift of the receiving side voltage will affect the working state of the inverter and lose the zero phase angle (Zero Phase Angle, ZPA) characteristics, which will lead to reduced system efficiency. The use of pulse density modulation (Pulse Density Modulation, PDM) also has the problems of low control sensitivity and significantly increased output voltage ripple. Therefore, how to achieve precise control of WPT output voltage while ensuring the compactness of the system is an important problem that needs to be solved in current technology. Summary of the invention

[0005] In view of the defects and deficiencies of the prior art and the actual needs, the present invention proposes a compact wireless power transmission system based on independent voltage control on the receiving side, which mainly includes the design of coupling mechanism and PWM control method. The anti-offset coupling mechanism is designed according to the specific performance requirements of the compact WPT system, and further by controlling the duty cycle of the active rectifier on the receiving side, high power density and wide range output voltage regulation are achieved.

[0006] The present invention provides a compact coupling mechanism with strong anti-offset performance by combining a solenoid structure, a reverse winding and a grooved core, which can effectively reduce the mutual inductance fluctuation within the offset range. The grooved core structure is used for embedding power converters, which can effectively improve the system power density and system integration. The system further realizes independent regulation of the output voltage without communication by performing pulse width modulation (PWM) on the active rectifier on the receiving side.

[0007] The technical solution adopted by the present invention to solve the technical problem is:

[0008] A compact wireless power transmission system based on independent voltage control on the receiving side: both the transmitting coil and the receiving coil are wound with multi-layer, multi-turn solenoid coils; a groove-type ferrite core is arranged on the inner side of the solenoid coil to form a magnetic shielding space for arranging an inverter or a rectifier.

[0009] Furthermore, a reverse winding connected in series with the transmitting coil is arranged on the inner side of the transmitting coil to balance the mutual inductance of the facing and offset positions; a phase detection auxiliary coil is arranged at the bottom of the receiving coil, the outer auxiliary coil is in the same direction as the receiving coil, and the internal auxiliary coil is in the opposite direction to the receiving coil, so as to eliminate the cross coupling between the auxiliary coil and the receiving coil.

[0010] Furthermore, a symmetrical half-bridge inverter is used on the transmitting side, and an active full-bridge rectifier is used on the receiving side.

[0011] Furthermore, by controlling the duty cycle of the active full-bridge rectifier on the receiving side, an odd-symmetrical three-level voltage is generated to achieve independent regulation of the output voltage.

[0012] Furthermore, PWM control is adopted on the receiving side.

[0013] Compared with the prior art, the outstanding features and advantages of the present invention and its preferred embodiments include at least:

[0014] (1) A compact coupling mechanism is proposed, which combines the solenoid coil and the reverse winding structure to reduce the mutual inductance fluctuation when the WPT system is offset and effectively improve the anti-offset performance of the coupling mechanism.

[0015] (2) The groove design of the coupling mechanism solves the problem that the existing technology is difficult to achieve high system integration and high power density.

[0016] (3) A receiving-side PWM control method is proposed. By adjusting the duty cycle of the three-level voltage, a wide voltage regulation range is achieved while ensuring that the working state of the primary inverter ZPA is not affected, and no communication between the transmitting side and the receiving side is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0018] Figure 1 An example diagram of a compact coupling mechanism proposed in an embodiment of the present invention, wherein: (a) 3D model (b) along the YOZ section;

[0019] Figure 2 A circuit diagram of a wireless power transmission system with PWM control on the receiving side according to an embodiment of the present invention;

[0020] Figure 3 This is a key waveform diagram of the receiving-side PWM control according to an embodiment of the present invention;

[0021] Figure 4 Schematic diagram of the working modes of the active rectifier according to an embodiment of the present invention, wherein: (a) Mode 1, (b) Mode 2, (c) Mode 3, and (d) Mode 4. DETAILED DESCRIPTION

[0022] In order to make the features and advantages of this patent more obvious and easy to understand, the following embodiments are specifically described in detail as follows:

[0023] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0024] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0025] The embodiment of the present invention specifically introduces the solution as follows:

[0026] The compact coupling mechanism proposed in this embodiment is as follows Figure 1As shown in (a), it consists of a transmitting coil, a receiving coil, a reverse winding, a phase detection auxiliary coil and a groove-type magnetic core. The cross section of the coupling mechanism along the YOZ parallel plane is shown in Figure 1 (b) as shown.

[0027] Both the transmitting coil and the receiving coil adopt a multi-layer, multi-turn solenoid winding method, which can utilize the maximum coil outer diameter in a limited volume to achieve the maximum magnetic field coupling. The transmitting coil has 3 layers with a total of 9 turns, and the receiving coil has 3 layers with a total of 6 turns. The transmitting coil is designed with a single-layer 2-turn reverse winding, which is connected in series with the transmitting coil to balance the mutual inductance of the positive and offset positions, reduce the mutual inductance fluctuation, and achieve strong anti-offset capability. A phase detection auxiliary coil is designed at the bottom of the receiving coil. The peripheral auxiliary coil is in the same direction as the receiving coil, and the internal auxiliary coil is in the opposite direction to eliminate the cross-coupling between the auxiliary coil and the receiving coil. A groove-type ferrite core is placed inside the solenoid coil to construct a magnetic circuit with low magnetic resistance and further enhance coupling. The top (bottom of the receiving side) magnetic core and the side wall magnetic core form a groove, forming a magnetic shielding space inside for placing an inverter or rectifier.

[0028] Independent PWM control scheme on the receiving side:

[0029] Although the proposed coupling mechanism can ensure the stable mutual inductance fluctuation within the offset range, due to the existence of parasitic parameters such as the internal resistance of the coil and the device, it is still difficult for the WPT system to achieve accurate and controllable output voltage under different offset positions and load conditions. Therefore, the present invention proposes a PWM control method for an active rectifier on the receiving side, which generates an odd-symmetrical three-level voltage by controlling the duty cycle of the active rectifier, thereby achieving independent and accurate output voltage regulation.

[0030] The equivalent circuit topology structure of the receiving side PWM control WPT system proposed in the present invention is as follows: Figure 2 The transmitting side uses a symmetrical half-bridge inverter and the receiving side uses an active full-bridge rectifier. IN (V O ),v P (v S )、L P (L S )、M、C O , R L They represent the DC voltage on the transmitting side (receiving side), the AC voltage at the midpoint of the bridge arm, the coil self-inductance, the mutual inductance, the output filter capacitance and the load resistance. F is the inverter output current, i P with i S are the primary and secondary coil currents respectively. EQP and Z EQS are the equivalent impedances of the inverter and rectifier respectively. F , C F , CP , C S is the LCC-S compensation parameter, and its resonance relationship is:

[0031]

[0032] Where ω is the system operating angular frequency.

[0033] The fundamental component of the rectifier input voltage V S(1) for:

[0034]

[0035] From formula (2), we can know that the fundamental voltage V S(1) Constant and load-independent.

[0036] Combination Figure 3 , Figure 4 The working mode of the receiving side PWM control of the present invention is described. Taking the output voltage of the transmitting side inverter as the phase reference, D S It represents the duty cycle of the upper tubes S3 and S5 of the rectifier, and the corresponding PWM signals of the lower tubes are complementary to them. The key waveforms on the receiving side are as follows: Figure 3 shown.

[0037] According to the switching action and current direction on the receiving side, one cycle can be divided into four modes.

[0038] 1) Mode 1 [t0-t1], such as Figure 4 (a) shows that during the dead time around time t0, the receiving coil current i S is positive, charging the output parasitic capacitance of S3 and discharging the output parasitic capacitance of S6, and the switch tubes S3 and S6 are turned on at zero voltage. From t0 to t1, S3 and S6 are continuously turned on, and the current i S To load R L Power supply and output filter capacitor C O Charge.

[0039] 2) Mode 2[t1-t2], such as Figure 4 (b) As shown: At t1, S3 is turned off and S4 is turned on. From t1 to t2, S4 and S6 are continuously turned on, and the rectifier input voltage v S is short-circuited, the current i S The load is not connected to the output filter capacitor C. O powered by.

[0040] 3) Mode 3 [t2-t3], such as Figure 4 (c) shows: At time t1, the current i S Natural commutation: From t2 to t3, S4 and S6 are continuously turned on.

[0041] 4) Mode 4 [t3-t4], such as Figure 4 (d) shows that during the dead time around time t3, the current i S is negative, charging the output parasitic capacitance of S5, S5 is turned on at zero voltage, and S6 is turned off. From t3 to t4, S4 and S5 are continuously turned on, and the current i S To load R L Power supply and output filter capacitor C O Charging. At t4, the next cycle begins.

[0042] The fundamental approximate value of the inverter input voltage in each mode within the cycle and the fundamental V S(1) The amplitude and phase are the same, and the voltage gain G of the active rectifier can be obtained. V for:

[0043]

[0044] By adjusting the duty cycle D S , precise output voltage control can be achieved.

[0045] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0046] This patent is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of a compact wireless power transmission system based on independent voltage control on the receiving side under the inspiration of this patent. All equal changes and modifications made according to the scope of the patent application of the present invention should be covered by this patent.

Claims

1. A compact wireless power transmission system based on independent voltage control at the receiving side, characterized in that: The transmitting coil and the receiving coil are both formed by winding multi-layer, multi-turn solenoid coils; a groove-type ferrite core is arranged inside the solenoid coil to form a magnetic shielding space for arranging an inverter or a rectifier.

2. A compact wireless power transmission system based on independent voltage control at the receiving side according to claim 1, characterized in that: A reverse winding connected in series with the transmitting coil is arranged on the inner side of the transmitting coil to balance the mutual inductance of the facing and offset positions; a phase detection auxiliary coil is arranged at the bottom of the receiving coil, the peripheral auxiliary coil is in the same direction as the receiving coil, and the internal auxiliary coil is in the opposite direction to the receiving coil, so as to eliminate the cross coupling between the auxiliary coil and the receiving coil.

3. A compact wireless power transmission system based on independent voltage control at the receiving side according to claim 2, characterized in that: A symmetrical half-bridge inverter is used on the transmitting side, and an active full-bridge rectifier is used on the receiving side.

4. A compact wireless power transmission system based on independent voltage control at the receiving side according to claim 3, characterized in that: By controlling the duty cycle of the active full-bridge rectifier on the receiving side, an odd-symmetrical three-level voltage is generated to achieve independent regulation of the output voltage.

5. A compact wireless power transmission system based on independent voltage control at the receiving side according to claim 3, characterized in that: PWM control is adopted for the receiving side.

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