A wireless power transmission device, method and system

Abstract

The present invention describes a wireless power transmission system, method and apparatus for wireless power transmission. The wireless power transmission system, method and apparatus allow the transmitter and the receiver to perform self-positioning correction to align them, thereby improving the power transmission efficiency. Each transmitter and the receiver has an alignment coil (DC coil) in addition to a wireless power transmission / receiving coil (AC coil). When the alignment coils of the transmitter and the receiver are magnetized with different magnetic poles, they attract each other. At least one of the transmitter or the receiver is mounted on a movable mechanism that allows the transmitter or the receiver to move therewith for self-correction positioning.

Description

Technical Field

[0001] The present invention relates to power charging, and in particular to wireless power transmission.

[0002] background

[0003] Electric vehicles (EVs) have become increasingly popular in recent years, with an estimated 40 to 70 million EVs on the road by 2025. Wireless power transfer (WPT) systems are becoming increasingly popular in EVs, primarily as an enabling technology for autonomous vehicles. With 85 million autonomous vehicles expected to be in use by 2035, there is a need for a charging infrastructure that does not require driver intervention. WPT systems enable fully automatic charging in a very short time when the EV is parked, while reducing battery size requirements. WPT systems are also much safer than wired charging systems, as the risk of electric shock and cable tripping is eliminated.

[0004] However, the inevitable misalignment between the transmitter and receiver reduces the efficiency of the charger, which is a major obstacle to the application of wireless power transfer systems. The main reason for the reduction in charger efficiency is the reduction in mutual inductance between the transmitter and receiver coils due to coil misalignment. Several different coil structures have been proposed in the literature to improve the misalignment tolerance. However, even these structures cannot alleviate the drop in efficiency when the misalignment distance approaches the size of the coil. Therefore, large transmitter coils are usually used in wireless power transfer systems, which is not realistic in electric vehicle applications.

[0005] Research in wireless power transfer has focused on accommodating the large gap between the charging pad and the chassis of a passenger electric vehicle while improving misalignment tolerance. However, existing systems that have been developed to date are impractical due to design constraints and high costs of electric vehicles.

[0006] Therefore, there remains a great need for devices, methods and / or systems that can achieve additional, alternative and / or improved wireless power transfer.

[0007] According to one aspect of the present invention, a wireless charging system for charging an electric vehicle (EV) battery is disclosed, the system comprising: a support structure; a wireless power transmitting device movably connected to the support structure, the wireless power transmitting device having a transmitter alternating current (AC) coil and a transmitter direct current (DC) alignment coil; and a transmitting controller connected to the wireless power transmitting device, the transmitting controller supplies power to the DC alignment coil to align the AC transmitter coil with the electric vehicle wireless power receiving device, thereby charging the electric vehicle battery.

[0008] In another aspect of the above system, the DC alignment coil aligns the power transmitting device with a receiver DC alignment coil of the wireless power receiving device of the electric vehicle.

[0009] In another aspect of the above system, the transmitter controller initiates a current to the transmitter DC alignment coil to magnetize the transmitter DC alignment coil to a primary polarity opposite to the secondary polarity of the electric vehicle receiver DC alignment coil.

[0010] In another aspect of the above system, a magnetic force is generated between the transmitter DC alignment coil and the receiver DC alignment coil, which causes the wireless power transmitting device to move in at least one direction along the support structure to align the transmitter AC coil and the receiver AC coil.

[0011] In another aspect of the above system, when the transmission controller determines that the transmitter AC coil of the wireless power transmission device and the electric vehicle receiver AC coil are aligned, power provided to the AC transmitter coil induces current in the AC receiver coil to charge the electric vehicle battery.

[0012] In another aspect of the above system, when an electric vehicle is detected, the transmitter controller initiates the supply of current to the transmitter DC alignment coil.

[0013] In another aspect of the above system, the electric vehicle detection includes wirelessly receiving, at the transmitting controller, a command issued from an electric vehicle receiver controller.

[0014] In another aspect of the above system, when the transmitter DC alignment coil and the receiver DC alignment coil are aligned, the supply of current to the transmitter DC alignment coil is stopped.

[0015] In another aspect of the above system, the alignment of the transmitter DC alignment coil and the receiver DC alignment coil is determined by detecting a disturbance current in the transmitter AC coil or the receiver AC coil.

[0016] In another aspect of the above system, the gap distance between the transmitter AC coil and the receiver AC coil is determined by sweeping the perturbation frequency of the perturbation current within a certain frequency range.

[0017] In another aspect of the above system, a peak value of the disturbance current from the frequency sweep determines a minimum gap separation between the AC transmitter coil and the receiver AC coil.

[0018] In another aspect of the above system, if the minimum gap separation is greater than a threshold, the transmit controller issues an instruction to the controller to move the vehicle closer to the wireless power transmission device.

[0019] In another aspect of the above system, the transmitter DC alignment coil and the transmitter AC coil are arranged perpendicular to each other.

[0020] In another aspect of the above system, the transmitter AC coil is any one of a spiral type coil, a DD type coil, and a solenoid type coil.

[0021] In another aspect of the above system, the transmitter DC alignment coil includes a DC magnetic core and the AC transmitter coil includes an AC magnetic core.

[0022] In another aspect of the above system, the DC core is made of steel.

[0023] In another aspect of the above system, the AC core is made of ferrite.

[0024] In another aspect of the above system, the transmitter AC coil is made of Litz wire.

[0025] In another aspect of the above system, the transmitter DC alignment coil is made of enameled wire or copper conductor.

[0026] In another aspect of the above system, the support structure can be any one of a linear slide, a ball screw arrangement, a pulley and belt arrangement, and a wheel and guide arrangement.

[0027] In another aspect of the above system, the support structure includes two linear slides configured to allow movement in two directions.

[0028] In another aspect of the above system, the transmitter AC coil includes a plurality of ferrite rods.

[0029] In another aspect of the above system, the plurality of ferrite rods have unequal spacing.

[0030] In another aspect of the above system, the wireless power transmitting device further comprises a copper shield made of a continuous copper sheet.

[0031] In another aspect of the above system, the wireless power transmitting device moves horizontally along the support structure.

[0032] According to another aspect of the present invention, a wireless charging system for charging an electric vehicle (EV) battery is disclosed, the wireless charging system comprising: a wireless power receiving device mounted on the electric vehicle, the wireless power receiver device having a receiver alternating current (AC) coil and a receiver direct current (DC) alignment coil, which are connected to the battery of the electric vehicle; and a controller connected to the wireless power receiver device, the controller powering the receiver DC alignment coil to align the transmitter DC coil of the wireless power transmitting device with the wireless power receiver.

[0033] In another aspect of the above system, the DC alignment coil of the wireless power transmitting device is moved horizontally by the magnetic field of the transmitter DC alignment coil and the receiver DC alignment coil connected to the battery of the electric vehicle.

[0034] In another aspect of the above system, when the DC receiver alignment coil is aligned with the transmitter DC alignment coil, the receiver AC coil inductively receives power from the transmitter AC coil of the wireless power transmitting device to charge the electric vehicle battery.

[0035] In another aspect of the above system, the receiver AC coil can power the transmitter AC coil from the electric vehicle battery.

[0036] In another aspect of the above system, the controller initiates a current to the transmitter DC alignment coil to magnetize the transmitter DC alignment coil to a primary polarity opposite to a secondary polarity of the electric vehicle receiver DC alignment coil.

[0037] In another aspect of the above system, the controller wirelessly sends a command to the wireless power transmitter to initiate alignment and charging of the electric vehicle battery.

[0038] In another aspect of the above system, when the transmitter DC alignment coil and the receiver DC alignment coil are aligned, the supply of current to the receiver DC alignment coil and the transmitter DC alignment coil is stopped.

[0039] In another aspect of the above system, the alignment of the transmitter DC alignment coil and the receiver DC alignment coil is determined by measuring a disturbance current in the transmitter AC coil or the receiver AC coil.

[0040] In another aspect of the above system, the disturbance frequency of the disturbance current is swept within a certain frequency range to determine the gap distance between the transmitter AC coil and the receiver AC coil.

[0041] In another aspect of the above system, a peak current of the perturbation current from the frequency sweep is utilized to determine a minimum gap separation between the transmitter AC coil and the receiver AC coil.

[0042] In another aspect of the above system, if the minimum gap separation is greater than a threshold, an indication is provided to the controller to move the vehicle closer to the wireless power transmitter.

[0043] In another aspect of the above system, the receiver DC alignment coil and the receiver AC coil are arranged perpendicular to each other.

[0044] According to yet another aspect of the present invention, a wireless charging system including a transmitter side and a receiver side is disclosed for charging an electric vehicle (EV) battery according to the above aspects.

[0045] According to another aspect of the present invention, a method for wirelessly charging a battery of an electric vehicle (electric vehicle) is disclosed, the method comprising: receiving an indication to start aligning a transmitter DC alignment coil of a wireless power transmitting device with a receiver DC alignment coil connected to the electric vehicle; supplying current to the transmitter DC alignment coil; checking the alignment of the transmitter DC alignment coil with the receiver DC alignment coil; when the alignment is confirmed, supplying current to the transmitter AC coil to inductively charge the electric vehicle battery through the receiver AC coil.

[0046] In another aspect of the above method, a method of checking the alignment of a transmitter DC alignment coil with a receiver DC alignment coil includes detecting an AC self-inductance of a disturbance current of the transmitter AC alignment coil.

[0047] In another aspect of the above method, the method further includes varying the frequency of the perturbation current within a defined frequency range to determine a distance between the transmitter DC alignment coil and the receiver DC alignment coil.

[0048] In another aspect of the above method, when alignment is verified, power to the transmitter DC alignment coil is stopped. Power to the DC alignment coil is stopped after alignment is confirmed.

[0049] In another aspect of the above method, the transmitter DC alignment coil is connected to a transmitter AC coil constituting a wireless power transmitting device, wherein the wireless transmitting device is horizontally movable along a support structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] More features and advantages of the present invention will be shown in the following detailed description in conjunction with the accompanying drawings, in which:

[0051] Figure 1 (a) to (c) show three commonly used wireless power transmission coils;

[0052] Figure 2 (a) and 2(b) show the mutual inductance of spiral, DD, and solenoidal coils normalized to the mutual inductance when aligned as a function of the normalized misalignment distance in the x and z directions, respectively;

[0053] Figure 3 The transmitter and receiver of the wireless power transfer system were demonstrated;

[0054] Figure 4 (a) to (c) show possible alignment features for transmitting and receiving devices;

[0055] Figure 5 Demonstrated wireless power transfer systems and devices for charging electric vehicles;

[0056] Figure 6An overview of wireless power transfer systems for charging electric vehicle batteries was presented;

[0057] Fig. 7A The electrical structure of the wireless power transfer system is presented;

[0058] Figure 7B The control block diagrams of the transmitting controller and the receiving controller are shown;

[0059] Fig. 8A Demonstrated self-correcting positioning and wireless power transfer operation of a wireless power transfer system during car battery charging;

[0060] Figure 8B A timing diagram showing the position correction control sequence;

[0061] Fig. 9 The simulated self-inductance of the AC coil corresponding to different horizontal misalignment distances is shown;

[0062] Fig.10 (a) shows a fixed duty cycle v perturb ,、i perturb and Z tank Typical waveform of

[0063] Fig.10 (b) shows the PI controlled v perturb , Adjustment perturb and the resulting Z tank Typical waveform of

[0064] Fig.11 The simulated self-inductance of the AC coil corresponding to different gap distances is shown;

[0065] Fig.12 (a) shows the v of PI control when Δy is large perturb 、i perturb 、i perturb,pk and Z tank Typical waveform of

[0066] Fig.12 (b) shows the PI control v when Δy = 50 mm perturb 、i perturb 、i perturb,pk and Z tank Typical waveform of

[0067] Fig.13 A wireless power transmission device comprising (a) a secondary electromagnetic coil, (b) a solenoid-type coil mounted in an electromagnetic coil with unequal spacing between ferrite rods, and (c) a solenoid-type coil mounted in an electromagnetic coil with equal spacing between ferrite rods is shown;

[0068] Fig.14A Shows h ext =25mm, I dc = Simulated electromagnetic force F at 30A mag , x The corresponding relationship between d and

[0069] Fig. 14B Shows d = 8mm, I dc = Simulated electromagnetic force F at 30A mag , x With the DC core increasing h ext The corresponding relationship between them;

[0070] Fig.15A and 15B The corresponding relationships between the simulated mutual inductance and (a) the misalignment distance Δx in the x direction and (b) the gap distance Δy are shown respectively;

[0071] Fig.16 The normalized mutual inductance of spiral, DD, and solenoidal coils as a function of the normalized misalignment distance in the z direction is shown;

[0072] Fig.17A and 17B The simulated system efficiency corresponding to different horizontal misalignment distances Δx and the loss classification of the dual-coil device for 5kW wireless power transmission are shown respectively;

[0073] Fig.18A and 18B The simulated magnetic field during 5kW wireless power transmission at (a) Δx = 0 mm and (b) Δx = 80 mm before misalignment correction is shown.

[0074] Fig.19A and 19B I dc = Simulated F at 30A mag , x The corresponding relationship between Δx and Δz;

[0075] Fig. 20 The magnetic induction intensity distribution of the solenoid coil is shown. The increase of flux density at the edge of the solenoid leads to higher core loss.

[0076] Fig.21 A and 21B show the simulated magnetic induction intensity when (a) the ferrite rod spacing is 10 mm and (b) the ferrite rod spacing is optimal for 5 kW wireless power transmission;

[0077] Fig. 22 Demonstrates the relationship between simulated eddy current loss and shield thickness for 5kW wireless power transmission;

[0078] Fig.23 The eddy current distribution of (a) a continuous copper sheet and (b) multiple separated copper sheets is shown;

[0079] Fig.24 The simulated current density distribution of 5kW wireless power transmission for shields composed of (a) multiple separate copper sheets, (b) multiple separate copper sheets connected by thin copper tapes, and (c) a continuous copper sheet is shown.

[0080] Fig.25 Shown are (a) the charger experimental setup and (b) the wireless power transfer charger power electronics circuit board;

[0081] Fig.26 The measured DC coil current waveform is shown;

[0082] Fig. 27 The correspondence between the measured magnetic force and the misalignment distance Δx in the x direction is shown;

[0083] Fig.28 Shows different dc Corresponding DC coil position;

[0084] Fig.29 The DC coil positions corresponding to different gap distances Δy are shown;

[0085] Fig.30 The DC coil positions corresponding to different vertical misalignment distances Δz are shown;

[0086] Fig.31 The current and voltage waveforms of the converter are shown when the measured wireless power transmission power is 5kW;

[0087] Fig.32 Shown are the thermal images of (a) the wireless power transmission coil system, (b) the transmitter, and (c) the receiver MOSFETs at a wireless power transmission power of 5 kW.

[0088] Fig.33 Shows different V bat The efficiency and P bat The correspondence between the best P bat By manually adjusting V bus accomplish;

[0089] Fig.34 The corresponding relationship between the measured efficiency and Δy is shown. The best P bat By manually adjusting V bus accomplish;

[0090] Fig.35 The relationship between the measured efficiency and Δz is shown. The best Pbat By manually adjusting V bus accomplish;

[0091] Fig.36 (a) As a comparative example, the measured waveform of evenly spaced ferrite rods during 3.7 kW wireless power transmission is shown, and (b) an image of evenly spaced ferrite rods damaged after attempting 5 kW wireless power transmission is shown; and

[0092] Fig.37 Shown are the measured waveforms of ferrite rods with unequal spacing when (a) performing 3.7 kW wireless power transmission and (b) performing 5 kW wireless power transmission.

[0093] It should be noted that throughout the drawings, like features are identified with like reference numerals.

[0094] Detailed description

[0095] The present invention describes a wireless power transmission device, method and system. According to the present invention, the transmitting and receiving devices are configured to perform position self-correction to align with each other, thereby improving the power transmission efficiency. The receiving device can be set in an electric vehicle and electrically connected to the vehicle battery to charge the battery. The electric vehicle referred to herein can be anything that is electric and movable (for example, including but not limited to automatic vehicles, drones, robots, etc.). The transmitting device can be provided as part of a vehicle charging system. The transmitting and receiving devices can also be provided as part of a kit.

[0096] As described herein, in addition to having wireless power transmit / receive coils (AC coils), the transmitting and receiving devices each have an alignment coil (DC coil). At least one of the transmitting and receiving devices is movably connected to a support structure that allows the transmitting and receiving device mounted thereon to move along the support structure so as to align itself with the other of the transmitting or receiving devices. When the DC alignment coils of the transmitting and receiving devices are magnetized to different magnetic poles, they attract each other. In this way, the transmitter or receiver device, depending on which one is mounted on the support structure, or if both are mounted on the support structure, can be moved in front of the other unaligned device.

[0097] During the position correction process, the AC coil is used to detect the misalignment distance to evaluate whether the transmitter and receiver devices are aligned. The wireless power transmission system includes a transmit controller, which can evaluate the misalignment by applying a disturbance to the AC transmit coil. The transmit controller can then adjust the DC current provided to the DC alignment coil to facilitate alignment. If the misalignment distance is too large to be overcome by the movement of the transmitter device, the transmit controller can send a notification to the electric vehicle receiver controller to instruct the vehicle to move. The transmit controller can also send a notification to the receiver controller after the alignment is completed.

[0098] After the position self-correction operation is completed, the current supply to the DC alignment coil may be stopped while wireless power transmission is performed using the AC coil. Due to the improved alignment, the wireless power transmission efficiency is higher. In addition, the receiver controller may calculate the power received by the AC receiver coil and pass the received power to the transmitting controller so that the transmitting controller can adjust the amplitude / frequency of the AC voltage supplied to the AC transmission coil.

[0099] Reference Figure 1-37 , examples are described as follows.

[0100] Figure 1 (a) to (c) show three types of wireless power transmission coils provided on the receiver side 102 and the transmitter side 104 . Figure 1 (a) shows a helical coil 106, Figure 1 (b) shows a DD type coil 108, Figure 1 (c) shows a solenoid type coil 110. A ferrite core 112 is shown as the back yoke of the coil.

[0101] The spiral coil 106 is widely used in wireless power transmission due to its simple structure. The DD coil 108 is composed of two spiral coils arranged side by side. The flux linkage area of ​​the spiral and DD coils faces the opposite device. The flux linkage area of ​​the solenoid coil 110 faces the vertical surface of the opposite device.

[0102] As mentioned earlier, in wireless power transfer systems, the reduction in power transfer capacity and efficiency caused by the misalignment of the transmitter coil and the receiver coil is a key issue. The main reason is that the mutual inductance between the transmitter coil and the receiver coil decreases as the misalignment distance between the two increases.

[0103] Figure 2 (a) and (b) show the mutual inductance of spiral, DD, and solenoidal coils normalized to the mutual inductance when aligned as a function of the misalignment distance in the x and z directions, respectively. The misalignment distance is normalized to the width of the transmitter and receiver, which are the same width. Figure 2 In (a) and 2(b), line 202a and line 202b represent the mutual inductance of the spiral coil, line 204a and line 204b represent the mutual inductance of the DD coil, and line 206a and line 206b represent the mutual inductance of the solenoid coil.

[0104] For spiral coils, the mutual inductance decreases to zero when the misalignment distance is about 0.7 after normalization to the width of the transmitter and receiver, and wireless power transmission cannot be achieved. At this distance, although there is still magnetic flux passing through the receiving coil, the two magnetic fluxes in opposite directions completely cancel each other out. Within a certain range, beyond this distance, the mutual inductance will increase, but it will eventually decrease to zero.

[0105] The mutual inductance of the solenoid coil also has a similar variation trend in the x direction. However, in the z direction, the mutual inductance of the solenoid coil tends to gradually decrease, but not below zero.

[0106] The mutual inductance of a DD coil will never be less than zero in any direction; in particular, the characteristic in the z direction is achieved by changing the direction of the current passing through the coil, and the amount of change depends on the misalignment distance.

[0107] However, these results show that the mutual inductance of each type of coil is reduced to less than half when the normalized misalignment distance is 1.0 in both the x and z directions; in particular, the misalignment in the x direction causes a more significant reduction. The reduction in mutual inductance results in a higher current required to transmit the same power, a lower transmission efficiency, or in worse cases, insufficient power transmission.

[0108] In the wireless power transmission system and device described herein, in addition to the coil for wireless power transmission, the receiver and the transmitter each have an alignment coil for position correction. Moreover, at least one of the transmitter and the receiver is arranged on a support structure, which allows the respective receiver and the transmitter to move in one or more directions. After providing direct current to the DC alignment coils and magnetizing them with opposite polarities, a magnetic force is generated, which causes the respective receiver or transmitter device to move in front of the other device. In this way, the wireless power transmission system, method and device described herein provide for self-correction positioning between the transmitter and receiver coils.

[0109] Figure 3 The transmitter and receiver devices of the wireless power transmission system are shown. The transmitter device 302 and the receiver device 304 each have two coils: an AC transmitter / receiver coil for wireless power transmission between the transmitting device and the receiving device; and a DC alignment coil, which moves at least one device for position self-correction. It is worth noting that although the AC coil and the DC coil are Figure 3The wireless power transmitting / receiving devices may be substantially symmetrical to each other so as to achieve bidirectional power transmission.

[0110] exist Figure 3 In the exemplary transmitting device and receiving device shown, the AC coil includes an AC yoke. The structure of the AC coil can be arbitrary, and can be Figure 1 Any type of coil as described in (a) to (c). Figure 3 In the structure, a solenoid type coil is used. The AC coil can be made of twisted wire and the AC core can be made of ferrite, because these materials can suppress losses when operating at high frequencies. Twisted wire can effectively suppress losses caused by high-frequency currents.

[0111] The DC coil can be made of ordinary wire. The type of cable for the DC coil is not important (due to the low operating frequency). Enameled wire is much cheaper than stranded wire, so it can be used for the DC coil. Copper coils can also be used as DC coils. The DC core can be made of steel structure, because steel is cheap, has high mechanical strength and high magnetic field saturation, which are excellent characteristics that DC core materials should have.

[0112] The AC coil can be mounted inside a DC yoke of a U-shaped structure. This DC yoke can serve as a housing for the AC coil. The DC core and coil can be shielded with copper to prevent the AC flux from passing through them, thus avoiding hysteresis losses.

[0113] At least one of the transmitter and receiver devices is movably connected (e.g., directly or indirectly) to a support structure, such as a linear slide ( Figure 3 (not shown in Figure 2). Figure 5 As shown, the support structure allows the respective receiver or transmitter device to move in one or more directions. For example, when the transmitter and receiver are mounted vertically (such as Figure 3 The support structure may allow movement in the X and Z directions when the device is spaced a distance apart in the Y direction (as shown). The device may also be connected to a support structure that allows movement in the Y direction (e.g., via a spring).

[0114] When the DC coils on the two side units are magnetized with different poles, the DC coils attract each other so that the transmitter and receiver units are aligned. The DC core is the path for the magnetic flux, which creates a force to align.

[0115] Figure 4 (a) to (c) show various alignment components that can be used for transmitting and receiving devices. Figure 4 One of the configurations shown in (a) to (c) may be substituted Figure 3The DC coil and DC core shown in FIG. 1 can be used in the transmitter and receiver devices, or on either side thereof. Figure 4 (b) shows a set of permanent magnets (PMs) replacing the DC coils. This structure with PMs is thinner than the structure with DC coils. Figure 4 The structure of (a) consists of three parts: a magnetic core, a coil, and a permanent magnet. The magnetic field of the structure is enhanced by the permanent magnet and controlled by the coil. Both the transmitter and receiver devices can be used only Figure 4 The DC core in (c) produces the smallest electromagnetic force, but it is the simplest and lightest. However, at least one of the transmitter or receiver units should contain a DC coil to achieve or control alignment.

[0116] Figure 5 A wireless power transmission system and apparatus for charging an electric vehicle 510 is shown. Figure 5 As shown, the wireless power transfer system can be mounted on the front or rear of an electric vehicle, which creates a separation gap created by parking (e.g., the movement of the electric vehicle controlled by a human driver or a computer in a fully automated vehicle) rather than the suspension system of the electric vehicle. The smaller the gap, the better the magnetic coupling and the more compact the design. However, Figure 5 The configuration described in is not limited to this installation, and it can also be installed on the bottom of the electric vehicle 510.

[0117] The wireless power transmission system is composed of a power transmitting device 502, a power receiving device 504 and a supporting structure 506. For example, the transmitting device 502 and the receiving device 504 can be connected to Figure 3 The same device as shown in Figure 5 In the wireless power transmission system shown, the receiving device 504 is mounted on the rear side of the vehicle 510 and connected to the battery or other power storage device (such as a supercapacitor) of the vehicle 510 (not shown), while the transmitting device 502 is mounted on a support structure 506, which is mounted on a bracket or wall facing the rear of the vehicle and is connected to a power source (not shown). In some cases, in addition to the transmitting device 502 being mounted on the support structure 506, the receiving device 504 mounted on the vehicle 510 can also be mounted on a support structure (not shown) on the vehicle 510. In some cases, the receiving device 504 may be mounted on a trailer suspension bracket of the vehicle, which may provide a standard height. The receiver device 504 and / or the transmitter device are detachable. A wireless charging system for charging an electric vehicle battery includes a power transmitting device 502 and a support structure 506. The wireless power transmission system can be installed in the owner's home (i.e., garage), parking lot, commercial facility, industrial facility, charging station, etc.

[0118] like Figure 5As shown, the wireless power transmission system can be installed vertically (i.e., the transmitter device and the receiver device are installed vertically). Compared with horizontal installation, for example, the receiving device 504 is installed on the bottom of the vehicle 510, and the transmitting device 502 and the support structure 506 are installed on the ground, the vertical installation can reduce the gap between the transmitter device and the receiver device.

[0119] like Figure 5 As shown, when the transmitting device and the receiving device are installed vertically, the support structure 506 can be configured to allow the transmitting device 502 to move horizontally and be adjusted to align with the receiving device 504 on the vehicle 510, and the position of the receiving device 504 may be different each time the vehicle is parked. In this case, a linear slider can be used for the support structure 506. Without exceeding the scope of the present disclosure, those skilled in the art can also design alternative support structures 506 such as ball screw devices, pulley and belt devices, and wheels and guide devices.

[0120] When the height of the vehicle 510 is lowered due to the load, or based on different vehicle heights, the vertical position of the receiving device 504 may change. However, the vertical distance change caused by the load may be only 5cm-10cm, which is much smaller than the misalignment distance of the horizontal position. Therefore, the coils of the transmitter device and the receiver device adopt a solenoid type power transmission coil, and the tolerance of this type of coil in the Z direction can overcome the influence of the misalignment distance (see Figure 2 (b)), so that the system does not require additional mechanisms to handle alignment in the vertical direction.

[0121] In addition, the support structure 506 can allow the launch device 502 to move in multiple directions. For example, using two linear slides, the launch device 502 can move in the X and Z directions at the same time.

[0122] Figure 6 An overview of a wirelessly transmitted power system for charging electric vehicle batteries is shown. Figure 6 The wireless power transmission system shown can be bidirectional, and it can also be used to supply power from an electric vehicle to the ground or other equipment. The wireless power transmission system includes a system for wirelessly transmitting power to an electric vehicle, and the system includes a wireless power transmitting device 602 movably connected to a support structure 610. The wireless power transmitting device 602 includes an AC transmitter coil 604 and a transmitter DC alignment coil 606. The wireless power transmission system also includes a transmission controller 620. As shown in the figure, the transmission controller 620 includes a central processing unit, a non-transitory computer readable memory, a non-volatile memory, a communication module, and an input and output (I / O) interface. The non-transitory computer readable memory can store instructions, and when the CPU executes these instructions, the transmission controller will be configured to perform certain functions, such as referring to Fig. 8AFurther described.

[0123] The transmit controller is connected to the power converter 630, for example, through an I / O interface. Figure 6 The power converter 630 is capable of providing DC and AC power to / from the transmitter AC coil 604 and the transmitter DC alignment coil 606 from the mains 632. The power converter 630 is powered according to the control instructions from the transmission controller 620. In addition, one or more measuring devices 608 (such as sensors, voltmeters, ammeters, etc.) are installed on the power transmission device, and their measured values ​​are provided to the transmission controller 620. In this way, the transmission controller can adjust the control of the power converter 630 according to the measured values ​​received from the measuring device 608 to optimize power transmission.

[0124] Figure 6 Also depicted is an electric vehicle 650 that receives power from a wireless power transmission system (or transmits power from the electric vehicle to a wireless power transmission device 602). The electric vehicle includes a battery 660 or other energy storage device (such as a supercapacitor), a wireless power receiving device 652 electrically connected to the battery 660, and a power converter 680 between the battery 660 and the wireless power receiving device 652. The wireless power receiving device 652 includes a receiver AC coil 654 and a receiver DC alignment coil 656. The electric vehicle also includes a receiver controller 670. As shown, the receiver controller 670 includes a central processing unit, a non-transitory computer readable memory, a non-volatile memory, a communication module, and an input-output (I / O) interface. The non-transitory computer readable memory can store instructions that, when executed by the CPU, will configure the transmission controller to perform certain functions, such as referring to Fig. 8A Further described. One or more measuring devices 658 may be installed on the wireless power receiving device 652, and their measurements are provided to the receiver controller 670. In this way, the receiving controller can calculate the power received by the wireless power receiving device 652 based on the measurements received from the measuring devices 658, and pass this information to facilitate optimized power transmission. The I / O interface of the receiving controller 670 can also receive measurement readings from the battery management system (battery 660), such as charging status, etc.

[0125] In addition, the receiver controller 670 is configured to send an instruction to the transmitter controller 620 via the wireless communication interface to initiate a charging operation using the wireless power transmission device to initiate charging. The receiver controller 670 is configured to initiate a DC power supply from the battery 660 to the receiver DC alignment coil 656 to magnetize the receiver DC alignment coil 656 to a secondary polarity opposite to the primary polarity of the transmitter DC alignment coil 606. The transmitter controller is configured to initiate a DC current from the power supply 630 to magnetize the transmitter DC alignment coil 606 to the primary polarity. The transmitter controller 620 can also determine whether the transmitter DC alignment coil 606 and the receiver DC alignment coil 656 are aligned (thereby indicating that the transmitter AC coil 604 and the receiver AC coil 654 are aligned to achieve optimal power transmission). When it is determined that the transmitter DC alignment coil 606 and the receiver DC alignment coil 656 are aligned, the transmitter controller is configured to initiate an AC power from the power converter 630 to the wireless power transmitting coil 604 to generate induction between the transmitter AC coil 604 and the receiver AC coil 654. The induced alternating current in the wireless power receiving coil 654 is used to charge the battery 660 .

[0126] The transmitter and receiver controllers may be configured to communicate wirelessly with each other. For example, each transmitter and receiver controller may include a communication interface that allows communication using a standard protocol such as IEEE 802.11 (Wi-Fi TM ),IEEE 802.15.1(Bluetooth TM )) and IEEE 802.15.4 (ZigBee TM )Communication interface for communication.

[0127] FIG7 shows the electrical structure of the wireless power transmission system. The transmitter and receiver may have the same structure, each with three branches. One branch is used to power the DC coil and the other is used for the AC coil. The transmitter controller 620 and the receiver controller 670 are configured to control switches (M1-M6 and M7-M12, respectively).

[0128] The electrical structure shown in FIG7 includes a full-bridge converter for driving an AC coil for wireless power transmission and a half-bridge converter for driving a DC coil for misalignment correction. For example, in a transmitter device, a full-bridge inverter converts a bus voltage V bus This translates to an 85kHz square waveform with a 50% duty cycle. Fig. 7A As shown in Figure 1, the series (SS) compensation capacitor is selected to resonate at 85kHz due to its size and shape factors. Fig. 7AThe full-bridge converter shown acts as a synchronous rectifier to provide current to the EV battery. The symmetrical nature of the system architecture allows bidirectional power transfer; allowing vehicle-to-grid (V2G) operation in the proposed wireless power transfer system. An increasing number of bidirectional EV chargers are using V2G operation. V2G operation allows EV batteries to transfer power to the grid during peak hours and provide grid support functions.

[0129] Figure 7B The control block diagrams of the transmitter device and the receiver device are shown separately. The field programmable gate array (FPGA) performs the main control and generates the switch signals for M1-M12. The microcontroller unit (MCU) manages the mode indicating whether to perform position correction or wireless power transmission, and is connected to the FPGA through the communication interface. The MCU provides a reference to the FPGA controller based on the data of other devices, and transmits the data obtained from the FPGA to other devices through wireless communication.

[0130] FIG8 illustrates the self-correction positioning and wireless power transmission operation of the wireless power transmission system during the process of charging the battery of an automobile. When the electric vehicle stops / parks (802), the receiver controller indicates that the electric vehicle is ready to start the charging operation by wirelessly communicating with the transmitter controller (804). The transmitter controller is initialized to prepare for charging (806).

[0131] The position correction operation completes the alignment of the transmitter device and the receiver device. The DC branch provides a controlled DC current to the DC coils to magnetize them with different magnetic poles (808, 810). In order to ensure that misalignment correction is performed under all operating conditions, the DC coils will be enabled for a long enough time to provide a weak magnetic force. However, choosing to enable the DC coils for a long enough time will cause a waste of time and energy, and also increase component stress during the service life of the charger. In order to optimize this process, real-time impedance detection technology can be used. In addition, by placing the charger in the front / rear of the electric vehicle, the gap between the transmitter and the receiver can be smaller, and the wireless power transmission efficiency is higher. However, the gap size variation is also greater because it is highly dependent on the vehicle driver. In order to minimize the variation of the separation gap, a real-time resonant frequency tracking method can be used.

[0132] In order to optimally disable the DC coil and reduce alignment time, the distance between the transmitter and receiver must be measured. The AC branch of the transmitter device provides a small AC current to the AC coil to measure the misalignment distance based on the sensed current and voltage (812). The AC branch of the transmitter device can measure the misalignment distance using a variety of techniques.

[0133] Also refer to Fig. 7A and Figure 7B , the misalignment distance can be calculated using one or more of the following techniques:

[0134] 1) When switches M7-M10 are in the closed state (this operation is controlled by 732b), the transmitter device inputs a low current pulse controlled by 732a to the primary coil (transmitter AC coil) to measure the input impedance at 736a. The transmitter controller can calculate the misalignment distance based on the misalignment distance and impedance relationship lookup table 734a (stored in the memory).

[0135] 2) When switches M7-M10 are in the closed state (this operation is controlled by 732b), the transmitter device inputs a large AC current controlled by 732a to the primary coil (transmitter AC coil), and the receiver measures the transmission power at 734b. The receiver controller can calculate the misalignment distance based on the misalignment distance and power relationship lookup table 734a (stored in the memory), or the receiver controller can transmit the measured power to the transmitter controller to calculate the misalignment distance.

[0136] 3) When switches M7 and M8 or switches M9 and M10 are in the on state (this operation is controlled by 732b), the transmitter device inputs a low current pulse controlled by 732a to the primary coil (transmitter AC coil) to measure the input impedance at 736a. The transmitter controller can calculate the misalignment distance based on the misalignment distance and impedance relationship lookup table 734a (stored in the memory).

[0137] 4) When switches M6 and M7 or switches M8 and M9 are in the on state (this operation is controlled by 732b), the transmitter device inputs a low current pulse controlled by 732a to the primary coil (transmitter coil), and the receiver device measures the current through the secondary coil (receiver coil). The receiver controller can calculate the misalignment distance based on the misalignment distance and secondary coil current relationship lookup table 734a (stored in the memory).

[0138] Another method is to measure the resonant tank impedance Z tank , which involves the series capacitance C1 and self-inductance of the AC coil. tank is a function of the position of the charging plate, because the self-inductance coefficient L1 of the AC coil changes with △x, such as Fig. 9 Figure 1 shows the simulated self-inductance of the AC coil for different levels of misalignment distance. This method perturbs the voltage to regulate the current so that the duty cycle of the voltage becomes a measure of the resonant tank impedance. Therefore, the self-alignment time can be optimized by observing the duty cycle.

[0139] like Fig.10 As shown in (a), Z tank By applying a small perturbation V perturb Approximate calculation. By setting the frequency close to the resonant frequency f rThe disturbance frequency f s , loop current i perturb will be sinusoidal and its higher harmonics will be attenuated due to the high Q of the resonant tank. As the charging plates begin to align, i perturb increases and reaches its peak value when the compensation capacitor C1 resonates with the nominal L1. th , when i perturb >i th When the charging plate is aligned, the DC coil operation can be terminated in time. However, by applying a fixed V perturb ,i perturb When close to alignment, due to Z tank The high Q of the perturb and set Z tank Threshold, Z tank The threshold can be adjusted by V perturb Calculate.

[0140] To determine how to control V perturb , its effective value can be calculated according to the following formula:

[0141]

[0142] In the disturbance period T s The upper integral and average V perturb After that, its effective value can be given by the following formula:

[0143]

[0144] According to equation (2), v perturb,rms It can be controlled by the duty cycle D. Even, Z tank It can be calculated according to the following formula:

[0145]

[0146] When the transmitting plate is aligned with the receiving plate, due to the increase of L1, relative to the constant D, i perturb Therefore, if Fig.10 As shown in (b), the PI controller controls the duty cycle D to adjust i perturb Once Z tank Reduce to the threshold Z th Next, the alignment is completed and the DC coil stops working.

[0147] An important aspect of this technique is the perturbation frequency f s Once the DC coil is enabled, Z tank The impedance will change from capacitive to inductive. s ≈f r, due to the change of self-inductance, the threshold limit of D may occur earlier than the alignment, which will produce an obvious △x. To prevent this from happening, f s < <f r , which will result in Z tank Since the impedance is mainly capacitive and decreases monotonically, e.g. Fig.10 (b) As shown. Thus, when D<D th The alignment time is minimized under the conditions, and if the conditions are met, alignment is achieved. An impedance-based detection technique is proposed to optimize the misalignment correction, and the advanced controller also uses a resonant frequency tracker to minimize the gap variation, as described below.

[0148] In order to achieve DC coil correction misalignment, the system requires the electric vehicle to be parked with a separation gap of approximately 50 mm. However, the gap changes when the driver parks the vehicle, and the magnetic force F mag For larger △x, if the magnetic force F mag Not enough to overcome the linear slide friction F friction , the impedance-based detection technology proposed above will never be able to achieve the alignment condition D<D th Therefore, the driver must reduce the parking gap to improve alignment accuracy and efficiency. mag Similarly, L1 also decreases as the gap increases, such as Fig.11 As shown, this leads to a resonant frequency f r changes.

[0149] By real-time calculation of f r , the driver can adjust the separation interval to a smaller value. r The solution is to scan the disturbance frequency f s and measure i perturb Once i perturb >i th , the self-inductance of the AC coil begins to resonate with the compensation capacitor and f s ≈f r The disadvantage of this method is that perturb The peak value will depend on L1 changes, which may cause i th is never reached or is reached too early. Therefore, a more stable method is needed to determine f r .

[0150] Although I perturb The size of the change depends on the self-inductance, but i perturb Will be in f r The peak value is reached at L1 Offset Z C1 When Z tank Minimum. Fig.12As shown in (a), by tracking the i during the frequency scanning process perturb The peak value can determine the resonant frequency without considering the change of L1 during the alignment process. r After that, the system can use f r Minimize separation gaps.

[0151] If after the DC coil is operated, due to the magnetic force F mag Weaker, larger △x, L1 <L 1,nom Convert to f r >f r,nom ,like Fig.12 As the driver adjusts the electric vehicle to minimize the gap, L1 increases due to stronger coupling, and f r By setting a threshold f at the resonant frequency r,th , the driver can accurately measure the gap. Once f r =f r,th , the impedance-based detection technique can be applied again to reduce x, because the magnetic force F mag Bigger.

[0152] Based on the above, and again referring to FIG. 8 , it can be determined whether the transmitter and receiver are aligned ( 814 ). The controller can determine whether the measured distance between the transmitter and receiver is less than a threshold distance to determine whether they are aligned. If the transmitter and receiver devices are not aligned (No, at 814 ), it is determined whether there is a large misalignment gap ( 820 ), which can be based on the i ac_pk Detector (816) and execution f ac The scan (818) determines. In particular, the frequency f ac Scan and detect the peak current i ac_pk A gap between the coils may be indicated. If there is a large gap (yes, at 820), the transmit controller sends a message to the receiver controller that the vehicle needs to move position. If there is not a large gap (no, at 820), the transmit controller continues to perform DC current control (808). In some configurations, the frequency sweep and peak current determination can only be performed after the transmitter's DC alignment coil is as close as possible to the receiver's AC alignment coil, in which case, if adequate alignment is still not achieved, it may be that the transmitter / receiver devices are too far apart.

[0153] The timing diagram of the position correction control sequence is as follows: Fig. 8A The graph demonstrates the case where the separation gap ∆y is large, which is why alignment could not be achieved in the initial attempts. By correcting ∆y, the misalignment distance in the horizontal direction can be further reduced, resulting in more efficient wireless power transfer.

[0154] At the receiver device, based on the information received from the transmitter device, a position correction operation can determine whether the transmitter and receiver devices are aligned (822). The receiver controller determines whether there is a large gap (824), and if so (yes, at 824), the vehicle position is adjusted (826). If there is no large gap (no, at 824), the receiver device can continue to repeat the position correction operation by repeating the DC current control (810) until a positive indication is received from the transmitter controller that the transmitter and receiver devices are aligned. When the transmitter device determines that the transmitter and receiver devices are aligned (yes, at 814), the transmitter controller communicates this determination to the receiver controller by sending a notification to the receiver controller. The receiver controller determines that the transmitter and receiver devices are aligned (yes, at 822).

[0155] Once the transmitter unit and receiver unit are aligned, wireless power transfer begins. The DC alignment coil is idle and the AC coil begins transferring power from the transmitter unit to the receiver unit. The AC coil leg in the transmitter unit will operate as an inverter and provide high frequency power to the AC coil. The AC coil leg in the receiver unit will operate as a rectifier. Reverse power transfer (e.g., vehicle to grid) can be achieved by swapping the roles of these legs.

[0156] In addition to rectifying the AC power in the receiver unit, the receiver controller also communicates with the battery's battery management system (BMS), which sends instructions to the receiver controller to control the charging process. Power output data can be sent to the transmitter controller, which adjusts the mains voltage to adjust the transmission power. Once the battery is fully charged, the receiver notifies the transmitter to stop power transmission.

[0157] The receiver device performs power calculation (826). The power calculation can be performed using the induced voltage V out and current I ac_rx The power calculation unit 722b calculates the power P in the cycle, P = (V out ×I ac_rx ). The receiver controller is configured to send the result of the power calculation to the transmit controller. The transmit controller performs power control accordingly (828). The power control module includes generating switching signals for M1-M4 so that the actual transmitted power follows the required reference power level. The generation of the switching signal can be based on the received power calculation result. During the power transmission process, efficiency is continuously tracked (by comparing the transmitted power and the received power); if the two disagree (i.e., something went wrong, such as an object appearing between the two plates), for safety, the system can be shut down and restarted after a predetermined delay, or simply issue a warning to the system.

[0158] The receiver controller determines whether the vehicle battery is fully charged (830). If the battery is not fully charged (no, at 830), the wireless power transmission continues and the power calculation is performed (826). If the battery is fully charged (yes, at 830), the receiver controller notifies the transmit controller that charging is complete. The transmit controller determines whether charging is complete (832). If charging is not complete (no, at 832), the transmit controller continues to transmit power to the receiver device and performs power control (828). If charging is complete (yes, at 832), the transmit controller stops transmitting power to the receiver device and becomes idle (834). The vehicle can leave the power transmission system (836) and continue to park.

[0159] The operations described with reference to FIG8 are merely illustrative, and modifications may be made to this method without departing from the scope of the present disclosure. For example, the transmitter device may initiate charging operations with the receiver device, but not vice versa; the receiver device may be configured to determine alignment rather than the transmitter device; the receiver device in turn provides power to the transmitter device, etc.

[0160] The simulation and experimental results of a typical wireless power transfer system are now described.

[0161] Fig.13 A wireless power transmission device is shown, which consists of (a) a secondary electromagnetic base coil and (b) a solenoid coil installed in the electromagnetic base coil. Fig.13 The wireless power transmission device in the embodiment includes a transmitting device 1302 and a receiving device 1330 mounted on a supporting structure 1320. The transmitting device 1302 includes a steel core 1304 and a copper winding 1306, such as Fig.13 (a). Fig.13 As shown in (b), the transmitting device further includes a power transmitting coil 1308 made of (for example) twisted wire, a copper shield 1310 and a plurality of ferrite rods 1312.

[0162] Misalignment correction is performed by means of electromagnetic coils called DC coils, which generate a direct current between the devices. Fig.13 (a) The magnetic force F mag Self-alignment is possible because the launch plate is movably mounted on a support structure such as a low-friction linear slide that can move horizontally. Fig.13 As shown in (b), the power transfer coil, called the AC coil, begins wireless power transfer once alignment is complete.

[0163] Fig.13The dimensions of the transmitter device and the receiver device shown are shown in Table I. These dimensions can be set according to different power levels or gap distances. In order to achieve a compact design, the DC coil serves as the structural housing of the AC coil, and the two are integrated perpendicularly to each other. The coil orientation set in this way will weaken the magnetic induction intensity of the AC coil flowing through the DC core. However, during the wireless power transmission process, there is still leakage flux of the AC coil, which will generate eddy currents in the DC core, making shielding that can reduce DC core losses and improve transmission efficiency essential.

[0164] Table I: Dual Coil Charging Plate Dimensions

[0165]

[0166] The DC coil core is made of low-cost carbon steel. The DC coil uses standard copper windings instead of stranded wire. When the transmitter and receiver are aligned, the magnetic force F is enhanced due to the enhanced magnetic coupling. mag However, the magnetic force F mag The direction of the vector moves from the linear slider to the receiver, which will cause the magnetic force F mag,x Reduce, such as Fig.13 (a), which directly contributes to self-alignment. Therefore, in order to achieve a wide range of misalignment correction, the magnetic force F mag,x It must be large enough to overcome the linear slider friction caused by a misalignment distance equivalent to the width of the launcher, which is 200mm in this design.

[0167] The steel core thickness d affects the cost and weight of the charging system and should be selected to produce sufficient F mag,x ,like Fig.14A As shown. When d≤4mm, magnetic force F mag,x It is obviously reduced, and only when d≥6mm, the magnetic force F mag,x Therefore, d is chosen to be 8 mm to overcome the slider friction over a large range of x. A lighter core produces lower friction and lower core losses during wireless power transmission, but at the same time the magnetic force F mag will also decrease as d decreases; these can all be optimized.

[0168] like Fig.13 As shown in B, in order to further increase the magnetic force F mag , the DC steel core increases the height h ext By increasing the surface area of ​​the steel core, the flux linkage between the two coils increases, which makes the given i dc Magnetic force F under conditions mag Increase, such as Fig. 14B As shown. By increasing h ext , from 10mm to 25mm, magnetic force F mag,xFrom 3.99N to 5.04N, it increases by 26.3%. In this way, the magnetic force F mag,x The increase in is independent of d and therefore has little effect on the quality of the DC core.

[0169] The AC coil includes ferrite rods to improve magnetic coupling, while twisted wire is used for the windings to reduce skin effect losses. The designed ferrite rods optimize the inductance and magnetic coupling of the wireless power transfer coil. The ferrite rods are enclosed in a custom 3D printed housing that can withstand high temperatures while remaining lightweight. The height of the AC coil h sol Determined by the following formula:

[0170] sol = pad -2 ext (1)

[0171] where h pad =210mm,h ext = 25mm. The ferrite rods are spaced apart on the AC coil. The nominal AC coil design parameters are shown in Table II. Since the charging plate is located at the rear, the separation gap is not limited by the vehicle suspension which usually requires 120mm. A nominal separation gap of 50mm is feasible, which results in a coupling coefficient k of 0.41, which is 87.9% higher than the conventional coil design.

[0172] Table II: AC coil design parameters

[0173]

[0174]

[0175] The corresponding relationship between the simulated mutual inductance and the horizontal misalignment distance △x is as follows Fig.15A As shown. When △x ≥ 20mm, the mutual inductance begins to decrease rapidly. At △x = 100mm, the magnetic coupling between the devices is zero because the symmetrical position of the coils cancels the magnetic field. However, the self-alignment of the DC coils ensures a small △x, which leads to high mutual inductance during wireless power transfer. The separation gap has a greater impact on the charging operation because the dual-coil charging device cannot correct any y. As Fig. 15B As shown, the mutual inductance varies almost linearly with the separation gap. However, by utilizing the post-positioning of the system, the gap can be adjusted directly by the driver to maintain the high mutual inductance described.

[0176] Since one possible application of the proposed charger is a transport vehicle, the payload of the electric vehicle may cause a change in the compression of the shock absorber, which will cause a vertical misalignment z between the transmitter and receiver plates. Considering that the DC coil self-corrects the horizontal misalignment x, the structure of the AC coil is selected according to its tolerance to z. Figure 1The three coil structures shown, spiral coil, DD coil and solenoid coil, are compared to compare their mutual inductance with the vertical misalignment distance, as shown in Fig.16 As shown (DD type coil is represented by line 1602, solenoid type coil is represented by line 1604, and spiral type coil is represented by line 1606). Fig.16 , a solenoid coil structure was chosen because it maintains 18% of the rated mutual inductance for a 150% increase in vertical misalignment distance, normalized to a coil width of 200 mm.

[0177] The simulated magnetic field distribution of the coil system during misalignment correction and wireless power transmission is studied. To prevent magnetic field interference, the DC coil and AC coil are physically perpendicular to each other. This prevents the magnetic field from causing additional core losses in the DC coil steel core. During wireless power transmission, the magnetic field of the DC coil is almost zero due to the copper shielding.

[0178] Fig.17A The simulated efficiency versus misalignment distance △x during 5kW wireless power transmission is shown. The efficiency was determined by extracting a lumped element model of the coil structure using a finite element simulation tool, and then running a circuit-level simulation including non-ideal switching in PLECs. The losses caused by the magnetic field, including core losses and eddy current losses, were also calculated using the finite element analysis tool. The maximum efficiency reached 96.5% when the charging plates were perfectly aligned. The system maintained high efficiency until x=20mm. Fig. 17B Shows V out =400V, 5kW wireless power transmission power, loss classification of the dual coil charging board. Due to the use of solenoid coil structure, the eddy current loss in the shield is approximately equal to the eddy current loss in the ferrite core. However, as shown in Figure 15, the solenoid coil exhibits a better vertical misalignment tolerance, which is very important for EV payload.

[0179] The simulated magnetic field distribution of wireless power transmission power of 5kW in the two cases of x = 0 and 80mm is shown in Figure 18. When x = 0, the magnetic field is completely contained in the coil system, as shown in Figure 18(a). When x = 80mm, due to the weakening of the flux linkage between the AC coils, the magnetic field increases sharply to 15mT, and the transmitter current increases from 13.5A to rms Increased to 59.1A rms This is consistent with Fig.17A The efficiency drops sharply near x = 80 mm. Note that the efficiency at x = 100 mm is not shown because the current required is too large to achieve wireless power transmission.

[0180] The operation of the charger is not affected by the inefficient operating conditions caused by horizontal misalignment because wireless power transfer will not begin until the position correction is completed.

[0181] Fig.19A The simulated x-direction magnetic force F is shown mag , x Relative relationship with horizontal misalignment distance. When z=0mm, F mag , x The peak value is 5N, which can overcome the friction from △x=20mm to △x≥200mm, where 200mm is the width of the coil in this design. Similarly, even if △z=60mm, F mag , x It can also overcome the friction within the range of x. Assume I dc =30A, the minimum self-alignment time for x=200mm is 359ms when △z=0mm and 730ms when △z=60mm, which is much shorter than the time it takes for the DC coil temperature to reach saturation. Therefore, the thickness of the DC coil winding can be reduced. Vertical magnetic force F mag , z The relative relationship between the vertical offset z is as follows Fig.19B If z is very large, the DC coil can also solve the vertical misalignment problem in the z direction by using an additional linear slide and installing a balancing weight.

[0182] To achieve charging times comparable to conventional on-board wired chargers, the wireless power transfer system is designed as a Level 2 AC charging port rated at 5kW. However, at relatively high power transfers, the magnetic coupling of the coil needs to be increased to reduce leakage flux. To achieve this, separate ferrite bars are used in the solenoid coil because their low magnetic resistance guides the magnetic flux through the ferrite bars from the transmitter to the receiver. Due to the high cost of ferromagnetic materials, a minimum amount of ferrite is used. Customized ferrite bars are distributed in the solenoid coil to distribute the magnetic flux. Spacing is necessary, otherwise the strong magnetic induction intensity will cause high core losses, which will cause the temperature of the ferrite bar to increase. In order to understand the effect of ferrite bar spacing on power transfer, the magnetic induction intensity B in the solenoid coil needs to be analyzed. Fig. 20 The magnetic induction intensity distribution of the solenoidal coil is shown. The increase in the flux density at the edge of the solenoidal coil leads to higher core losses.

[0183] Assuming that a steady-state sinusoidal current flows in an infinitely long straight wire, a steady-state sinusoidal magnetic flux density B will be generated around the wire according to the following formula: wire :

[0184]

[0185] Where μ0 is the magnetic permeability, I is the current through the wire, and r is the distance from the wire.

[0186] Fig. 20 shows the magnetic flux density distribution of the solenoid coil. The ferrite rod placed near the center of the coil contacts the twisted wires on the front and back sides, causing them to pass a magnetic flux density of 2×Bwire. The twisted wire at the top of the solenoid coil is approximated as a straight wire, and the ferrite rods placed at the edge of the solenoid coil contact the three sides of the twisted wire, forming a magnetic flux density of 3×Bwire. The larger B causes the edge ferrite rods to have larger core losses compared to the ferrite rods near the middle. Large core losses limit the maximum transmitted power because the resulting core temperature rise cannot be reduced by convection cooling.

[0187] One potential solution is to use a single piece of ferrite instead of multiple strips, which reduces the magnetic resistance. This spreads the magnetic flux, resulting in lower B values ​​at the edges of the solenoid, at the expense of increased ferrite volume and cost. Another approach, which may be used in accordance with some embodiments, is to use ferrite rods with uneven spacing near the edges of the solenoid where the B values ​​are expected to be higher. Electromagnetic simulations were performed on an AC coil with a wireless transmission power of 5kW to determine the effect on the magnetic induction intensity distribution when the spacing of the ferrite rods was varied, as shown in Figure 2. Fig.21 As shown. Fig.21 As shown in Figure B, by increasing the density of ferrite rods near the edge of the AC coil, the peak magnetic induction intensity is reduced from 260mT to 208.2mT, a 20% reduction without increasing the total volume of ferrite material.

[0188] Although the ferrite rod increases the magnetic coupling, the solenoid coil structure still has significant leakage flux, which will induce eddy currents in the DC core. The resulting core loss is calculated according to the following formula:

[0189] P v = k·f a ·B b , (6)

[0190] Where P v is the time-averaged power per unit volume and is expressed in mW / cm 3 is the unit, f is the frequency and is measured in kHz, and k, b, and a are coefficients determined empirically based on the BH curve of the material. To mitigate this effect, a copper shield is placed between the AC and DC coils, such as Fig.13 (b) Although the shield reduces the loss in the steel core, the eddy current generated in the shield also causes ohmic loss. Due to the skin effect, the high-frequency eddy current mainly circulates within the penetration depth of 0.224mm, which is calculated as follows:

[0191]

[0192] Where δ is the penetration depth, ρ is the resistivity of copper, f is the frequency, and μ is the magnetic permeability of copper. To account for the skin effect, the shield thickness is varied in the simulation to reduce eddy current losses, such as Fig. 22 As expected, when the shield thickness is close to the penetration depth, below 0.3 mm, the eddy current loss P e A significant increase. By choosing a shield thickness of 0.5mm, a low eddy current loss of 49.3W was achieved without significantly increasing the total mass of the charging plate.

[0193] In order to optimize the copper shield design, the effects of using a continuous copper shield and multiple separate copper shields were compared. Since the steel core is U-shaped, the continuous copper sheet must be bent to completely shield the magnetic leakage of the steel core. Due to manufacturing defects, when the copper sheet is bent to cover the corners of the steel core, there is an air gap between the shield and the steel core, which causes DC core losses. Therefore, another alternative solution is to manufacture a shield composed of multiple separate copper sheets so that there is no gap. Since eddy currents are generated in the shield, the distribution of eddy currents in the shield composed of a continuous copper sheet and multiple separate copper sheets is studied.

[0194] like Fig.23 As shown in (a), the copper shield is exposed to a time-varying magnetic flux density B solenoid According to Faraday's law of electromagnetic induction, the reverse electromotive force (EMF) E is generated as follows:

[0195]

[0196] in It is B solenoid The magnetic flux in a certain area A. The electromotive force generates circulating eddy currents, which generate opposite magnetic induction intensity. In order to understand the current distribution of the shield composed of multiple separated copper sheets, the continuous copper sheet is divided into three pieces, such as Fig.23 (b) is shown. By doing so, the eddy currents are confined to each individual copper sheet, resulting in an increase in the current density near the boundary. For a continuous copper sheet, the eddy currents near the center are smaller because the eddy currents circulate along the edges of the copper sheet. Therefore, the eddy current losses caused by a shield composed of multiple copper sheets are greater than those caused by a shield composed of a continuous copper sheet.

[0197] Electromagnetic simulations were performed to observe the current density distribution in the copper shield, e.g. Fig.24 As expected, since the eddy currents are confined to each copper sheet, the current density along the copper sheet boundaries increases significantly, as shown in Fig.24 To reduce eddy currents, a copper tape with a thickness of 88.9 μm is used to electrically connect multiple separate copper sheets, so that eddy currents circulate around the entire shield.

[0198] In order to calculate the resistance of the copper tape in the simulation, each shield was connected to a copper tape with a thickness of 88.9 μm. Fig.24 As shown in (b), the copper tape significantly reduces the eddy current, and the peak current density is reduced from 1.08×10 9 A / m 2 Down to 8.13×10 8 A / m 2 This means that the eddy current loss from P e =238.4W reduced to P e = 69.6W, a 71% reduction. Although the copper tape does reduce eddy current circulation, the main limitation of the copper tape is that its thickness is much smaller than the copper tape penetration depth at 85kHz. Therefore, due to the skin effect, the current density along the boundary is still relatively high, such as Fig.24 (b) as shown.

[0199] To mitigate this effect, a shield consisting of a continuous copper sheet was simulated to observe the eddy current density, e.g. Fig.24 (c) The current density in the continuous copper sheet is much smaller, as shown in Fig.24 As shown in (c), the peak value is 5.74x10 7 A / m 2 , while the current density in the copper tape shield is 8.13x10 8 A / m 2 .exist Fig.24 In (a) and (b), the current density peak appears near the boundary of each copper sheet, while for continuous copper sheets, the current density peak remains relatively uniform, e.g. Fig.24 (c) This is mainly due to the thicker connection at each bend of the continuous copper sheet, which reduces the current density. In terms of eddy current loss, P e = 49.3W continuous copper sheet ratio P e = 69.6W, the copper tape shielding effect is much better, reducing it by 29%.

[0200] A prototype charger consisting of a coil system and power electronics was assembled, such as Fig.25 (a) The efficiency and alignment time of the dual-coil system were measured under different parameters, such as different separation gaps, vertical misalignment, and EV battery voltage, which characterizes its performance in its actual charging situation.

[0201] like Fig.25As shown in (b), all switches in the converter are silicon carbide (SiC) MOSFETs with forced air cooling. The system can also be liquid or air cooled, both on the transmitter and receiver sides. In addition, other power semiconductor technologies, such as silicon and gallium nitride, are also suitable. To achieve synchronous rectification, the AC coil current is sensed by a high-bandwidth Hall-effect current sensor, whose output is sampled by a parallel 10-bit analog-to-digital converter (ADC). A digital controller implemented on a field-programmable gate array (FPGA) uses a zero-crossing detection (ZCD) circuit to switch the MOSFETs when the AC current changes polarity.

[0202] To correct for misalignment, current pulses are applied to generate magnetic forces. The DC coil current is regulated using average current mode control (ACMC), such as Fig.26 As shown. Battery voltage V bat It will also detect to prevent the electric vehicle battery from overcharging. TM The module coordinates the flow of power between the transmitter and the receiver.

[0203] Fig. 27 Shows I dc The corresponding relationship between the magnetic force of the DC coil and △x at different times. The static friction and dynamic friction of the linear guide are measured to be 0.76N. Based on this measured friction, when 20mm<△x<240mm, I dc = 30 A, the magnetic force of the DC coil can overcome this friction. The prototype can correct horizontal misalignment within the range of △ x = 240 mm, which is 20% larger than the width of the device.

[0204] like Fig.28 As shown, during the alignment process, different I dc The wireless power transmission board is located below. dc When the current increases by 1.5 times from 20A to 30A, the alignment time decreases by 3.1 times from 6.2s to 2s. dc =30A, and when the misalignment distance between the charging plates △x = -11.5mm, overshoot occurs. According to Figure 17, this overshoot does not reduce the efficiency, and it remains relatively constant in the range of △x < 20mm.

[0205] The position correction process corresponding to different separation gaps Δy is as follows: Fig.29As shown. For small separation gaps, due to the large magnetic force at Δy = 50mm, the system can still be well aligned when the coil is overshooting and Δx = -11.5mm. Due to the overshoot, when Δy increases to 60mm, the alignment time is reduced from 2s to 1.75s, a reduction of 12.5%. However, when Δy increases from 50mm to 80mm, the magnetic force is significantly reduced, causing the alignment time to increase from 2s to 2.5s, an increase of 25%, and the alignment error increases from Δx = -11.5mm to Δx = 25mm.

[0206] The positions of the DC coils corresponding to different vertical misalignment distances Δz during the self-alignment process were also measured, e.g. Fig.30 As shown. When Δz is less than 25mm, which is close to 12.5% ​​of the coil width, the alignment time changes by 6.25%. Due to the larger magnetic force at Δz=0mm, a slight overshoot will occur, which will also cause a slight increase in the alignment time under ideal conditions. If the charging plate is adjusted to within 15mm, it is perfectly aligned, and the system can still correct horizontal misalignment up to Δz=40mm. In addition, it can be seen that when Δz=68mm, the alignment time increases by 25%. When Δz=68mm, the device will stop moving at a larger Δx, and it can be seen that Δx increases from 5mm to 78mm.

[0207] When the wireless power transmission power is 5kW, the voltage and current waveforms of the converter are as follows: Fig.31 As shown. bus Manual adjustment to achieve desired P bat The system efficiency, including the inverter, rectifier and coil losses, is 90.1% at 5kW wireless power transmission. The transmitter and receiver AC coils are respectively supplied with square wave AC voltage v ac_tx and v ac_rx The generated sinusoidal alternating current i ac tx and i ac rx This indicates that the SS compensation capacitors C1 and C2 resonate with the AC coil.

[0208] The proposed wireless power transfer charger was operated at 5 kW for 3 minutes to determine its preliminary thermal characteristics, such as Fig.32 The copper shield seems to reduce the core losses in the DC steel core. Fig.32 As shown in (a), the peak temperature of the charging board is 87.7°C, which appears on the receiver copper shield. The inverter / rectifier PCB uses a heat sink with a fan to force air cool the full-bridge converter. This results in peak temperatures of only 47.6°C and 49.7°C for the transmitter and receiver MOSFETs, respectively. Fig.32 As shown in (b) and (c).

[0209] like Fig.33 As shown, different V bat efficiency. bat ≥2.5kW, the efficiency remains relatively stable, with only a 2% change. Since the magnetic field connection between the AC coils requires a larger i ac _tx, so at low P bat The efficiency will be significantly reduced.

[0210] With modern parking sensors and onboard cameras, it is reasonable to expect that an electric vehicle should be able to park at a distance of 50 mm from the launch pad. However, in order to evaluate the changes in parking sensors, the efficiency corresponding to different separation gaps was measured, such as Fig.34 The efficiency decreases linearly with the separation gap, demonstrating the importance of minimizing the gap by placing the charger behind the electric vehicle. bat Under the condition of high P, the gap change has little effect, with only a 4.9% drop at 5 kW, compared with a 10.3% drop at 2 kW. bat Charge under the following conditions.

[0211] Considering that one possible application of such a charger is in transport vehicles, the charger plate will inevitably suffer from vertical misalignment depending on the payload of the electric vehicle. Fig.35 As shown, different P out Figure 2 shows the efficiency corresponding to vertical misalignment when Δz is ≤ 36 mm, which is approximately 18% of the width of the charging plate. The efficiency changes by only 1.4%, indicating good tolerance for small vertical misalignments. This is related to the performance of the position correction coil, which can tolerate vertical misalignment of up to 25% of the coil width. However, when Δz approaches 90 mm, which is approximately 45% of the width of the charging plate, the efficiency drops significantly. Also note that the overall efficiency drop is much smaller at 5 kW, at 7.7%, compared to a drop of 14.5% at 2 kW.

[0212] In order to vary the spacing of the AC coil ferrite rods, two custom 3D printed enclosures were fabricated; one Fig.13 (c) shows a spacing of 10 mm, and the other Fig.13 (b) shows uneven spacing. Fig.36 As shown in (a), the uniformly spaced ferrite rods were first successfully operated at a power level of 3.7 kW. However, the uniformly spaced ferrite rod coil failed when attempting to transfer 5 kW of wireless power. The resulting ferrite damage is shown in Figure 2. Fig.36 As shown in (b). As the main line voltage V busGradually increasing to achieve higher power transmission, the evenly spaced ferrite rods cannot achieve wireless power transmission above 4kW. It is worth noting that the visible damage to the ferrite is just below the strands, such as Fig.36 (b). This verifies Fig.21 The simulation results in A, Fig.21 In A, peak B is observed to appear below the AC windings of the top and bottom ferrite rods.

[0213] Non-uniformly spaced ferrite rods also operated successfully at a power level of 3.7 kW, as shown in Fig.37 (a). Then the wireless power transmission power is increased to 5 kW, and the coil with non-uniformly spaced ferrite rods successfully achieves steady-state operation with an efficiency of 90.1%, as shown in Fig.37 (b).

[0214] In view of the above, the wireless power transmission system, method and device disclosed in the present invention can self-correct the position and improve the efficiency of wireless power transmission. Compared with other types of charging systems, such as traditional wireless charging without a calibration mechanism and wired charging using a robotic arm, efficient wireless power transmission can be achieved through a smaller, lighter and more cost-effective system / device while maintaining scalability.

[0215] Table III compares several different charging methods, including vertically mounted wireless charging using the wireless power transfer systems, methods and apparatus described in the present disclosure, traditional wireless charging without an alignment mechanism, and wired charging using a robotic arm.

[0216] Table III - Comparison of autonomous charging methods

[0217]

[0218]

[0219] Those skilled in the art will appreciate that the systems and components shown in the figures may include components not shown in the drawings. In order to simplify and clarify the description, the elements in the figures are not necessarily scaled to scale, but are only schematic, and the element structure is not limited. It is obvious to those skilled in the art that some changes and modifications can be made without departing from the scope of the present invention.

Claims

1. A wireless charging system for charging an electric vehicle battery, comprising: a support structure to which a wireless power transmitting device is movably connected, the wireless power transmitting device having a transmitter AC transmitting coil and a transmitter DC alignment coil; and a transmitting controller connected to the wireless power transmitting device, the transmitting controller supplies power to the DC alignment coil to align the transmitter AC transmitting coil with a wireless power receiving device mounted on an electric vehicle to charge the battery of the electric vehicle; The transmitter DC alignment coil is aligned with the wireless power transmitting device and a receiver DC alignment coil on the electric vehicle wireless power receiving device; The transmitting controller initiates a current to the transmitter DC alignment coil to magnetize the transmitter DC alignment coil to a primary polarity opposite to the secondary polarity of the electric vehicle receiver DC alignment coil; Determining the alignment of the transmitter DC alignment coil and the receiver DC alignment coil by detecting a disturbance current in the transmitter AC transmitting coil or the receiver AC coil; Determine the gap distance between the transmitter AC transmitting coil and the receiver AC coil by scanning the disturbance frequency of the disturbance current within a certain frequency range; determining a minimum gap separation between the transmitter AC transmit coil and the receiver AC coil based on a peak value of the disturbance current from the frequency sweep; When the minimum gap separation is greater than a threshold, the transmission controller issues an instruction to a controller to move the vehicle closer to the wireless power transmission device.

2. The wireless charging system according to claim 1, wherein a magnetic force is generated between the transmitter DC alignment coil and the receiver DC alignment coil, and the magnetic force causes the wireless power transmitting device to move in at least one direction along the supporting structure to align the transmitter AC transmitting coil with the receiver AC coil of the wireless power receiving device.

3. According to the wireless charging system according to any one of claims 1 to 2, after detecting the electric vehicle, the transmitting controller starts supplying current to the transmitter DC alignment coil; when the transmitter DC alignment coil is aligned with the receiver DC alignment coil, the current supply to the transmitter DC alignment coil is stopped.

4. The wireless charging system according to any one of claims 1 to 3, wherein the transmitter DC alignment coil and the transmitter AC transmitting coil are arranged perpendicular to each other.

5. The wireless charging system according to any one of claims 1 to 4, wherein the transmitter DC alignment coil comprises a DC magnetic core, and the transmitter AC transmitting coil comprises an AC magnetic core; the DC magnetic core is made of steel, and the AC magnetic core is made of ferrite; the transmitter AC transmitting coil is made of stranded wire, and the transmitter DC alignment coil is made of enameled wire or copper wire.

6. The wireless charging system according to any one of claims 1 to 5, wherein the support structure is any one of a linear slider, a ball screw device, a pulley and belt device, a wheel and a guide device.

7. The wireless charging system according to any one of claims 1 to 6, wherein the support structure comprises two linear sliders movable in two directions.

8. The wireless charging system according to any one of claims 1 to 7, wherein the transmitter AC transmitting coil comprises a plurality of ferrite rods. 9 . The wireless charging system according to claim 8 , wherein the plurality of ferrite rods have unequal intervals.

10. The wireless charging system according to any one of claims 1 to 9, wherein the wireless power transmitting device further comprises a copper shield made of a continuous copper sheet.

11. The wireless charging system according to any one of claims 1 to 10, wherein the wireless power transmitting device moves in a horizontal direction along the supporting structure.

12. A wireless charging system for charging an electric vehicle battery, comprising: A wireless power receiving device mounted on an electric vehicle, the wireless power receiving device having a receiver AC coil and a receiver DC alignment coil, which are connected to a battery of the electric vehicle; and a receiving controller connected to the wireless power receiving device, the receiving controller energizing the receiver DC alignment coil to align a transmitter DC alignment coil of a wireless power transmitting device with the wireless power receiving device; The transmitting controller starts a current to the transmitter DC alignment coil to magnetize the transmitter DC alignment coil to a primary polarity opposite to the secondary polarity of the DC alignment coil of the electric vehicle receiver; Determining the alignment of the transmitter DC alignment coil with the receiver DC alignment coil by detecting a disturbance current in the transmitter AC transmitting coil or the receiver AC coil; Determine the gap distance between the transmitter AC transmitting coil and the receiver AC coil by scanning the disturbance frequency of the disturbance current within a certain frequency range; determining a minimum gap separation between the transmitter AC transmit coil and the receiver AC coil based on a peak value of the disturbance current from the frequency sweep; If the minimum gap separation is greater than a threshold, an indication is provided to a controller to move the vehicle closer to the wireless power transmitter.

13. The wireless charging system of claim 12, wherein a transmitter DC alignment coil of a wireless power transmitting device moves horizontally through the magnetic fields of the transmitter DC alignment coil and the receiver DC alignment coil connected to the battery of the electric vehicle; when the transmitter DC alignment coil is aligned with the receiver DC alignment coil, the current supply to the receiver DC alignment coil and the transmitter DC alignment coil is stopped.

14. The wireless charging system according to any one of claims 12 to 13, wherein the receiver AC coil can provide power to the transmitter AC coil from the electric vehicle battery.

15. The wireless charging system according to any one of claims 12 to 14, wherein the receiver DC alignment coil and the receiver AC coil are arranged perpendicular to each other.

16. A method for wirelessly charging an electric vehicle battery, the method comprising: receiving an indication to initiate alignment of a transmitter DC alignment coil of a wireless power transmitting device with a receiver DC alignment coil connected to an electric vehicle; Providing current to the transmitter DC alignment coil; checking the transmitter DC alignment coil and the receiver DC alignment coil; When alignment is confirmed, current is supplied to a transmitter AC transmitting coil to inductively charge the electric vehicle battery through a receiver AC coil; when aligned, the transmitter controller initiates a current to the transmitter DC alignment coil to magnetize the transmitter DC alignment coil to a primary polarity opposite to the secondary polarity of the electric vehicle receiver DC alignment coil; The power supply to the transmitter DC alignment coil is stopped after the alignment is confirmed; The method of checking the alignment of the transmitter DC alignment coil with the receiver DC alignment coil comprises detecting the AC self-inductance of the disturbance current in the transmitter AC alignment coil; By changing the frequency of the disturbance current within a limited frequency range, the distance between the transmitter DC alignment coil and the receiver DC alignment coil is determined; determining a minimum gap separation between the transmitter AC transmit coil and the receiver AC coil based on a peak value of the disturbance current from the frequency sweep; When the minimum gap separation is greater than a threshold, the transmission controller issues an instruction to the controller to move the vehicle closer to the wireless power transmission device.

17. The method of wirelessly charging an electric vehicle battery according to claim 16, wherein the transmitter DC alignment coil is connected to a transmitter AC coil constituting a wireless power transmitting device, wherein the wireless transmitting device is movable horizontally along a supporting structure.

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