Dynamic wireless power transfer system for controlling multiple transmitter coils

Abstract

A wireless power delivery system for a vehicle traveling along a surface is provided. The wireless power delivery system includes: a receiver coil mounted to the vehicle; a plurality of transmitter units connected in series and positioned on the surface; and a controller communicating with a voltage sensor of each transmitter unit. The transmitter units include inactive transmitter units and active transmitter units, and the inactive transmitter unit includes a leader transmitter unit and a trailing transmitter unit adjacent to the active transmitter unit. The controller is configured to: receive the voltages of the leader and trailing transmitter units, compare the voltages with data in a database, and determine the position of the receiver relative to the transmitter units to activate and deactivate the transmitter units as needed, dynamically modifying a subset of the active transmitter units to provide an efficient and smooth power supply to the receiver.

Description

[0001] Prior cross-reference

[0002] This application includes the entire contents of an international PCT application claiming priority to U.S. Provisional Application No. 63 / 065,256, filed August 13, 2020. Technical Field

[0003] This subject matter generally relates to inductive power transmission for mobile systems. More specifically, this subject matter generally relates to inductive power transmission for mobile systems on fixed guide rails, such as rail vehicles or rubber-tired vehicles operating in fixed lanes. Background Technology

[0004] U.S. Patent No. 10,473,012 discloses a wireless power transmission system that uses a single, long, vehicle-mounted receiver coil designed to receive power from multiple active transmitter units embedded in a track or surface beneath the vehicle. The receiver coil moves along a long row of transmitter units, activating a leading transmitter coil as it passes overhead and deactivating the last transmitter coil exposed by the receiver coil. The system functions as if a virtual single transmitter were present, moving with the receiver.

[0005] Therefore, a system and method for sensing the position of the receiver relative to the transmitter is needed as part of a control system for turning the transmitter on and off. Summary of the Invention

[0006] To meet the above and other needs, this disclosure provides a system and method for monitoring voltage changes in a transmitter unit as the receiver coil passes through the transmitter coil of the transmitter unit, and activating and deactivating the transmitter coil accordingly. By monitoring voltage changes in the transmitter unit, the wireless power transfer (WPT) system determines the position of the receiver relative to the transmitter unit and can effectively activate and deactivate the transmitter coil as needed.

[0007] The WPT system of this application includes a receiver coil mounted on the underside of a vehicle, such as a locomotive. Multiple transmitter units are embedded in the track, road, or path along which the vehicle travels. The receiver coil on the vehicle activates a subset of transmitter coils directly below the receiver coil, while the remaining transmitter coils not located below the receiver coil are inactive. As the vehicle moves along the track, the transmitter units within the subset of activated transmitter units change in response to the vehicle's movement. Furthermore, multiple locomotives may be equipped with receiver coils on their undersides, and different subsets of the active transmitter units within the series-connected transmitter units embedded in the track supply power to more than one receiver coil at a given time.

[0008] Each transmitter coil is mounted to a transmitter unit, which is connected in series with a power supply, a controller, and adjacent transmitter units. A high-frequency power supply provides power to the series of transmitter units via two power transmission lines. Jumpers or wires connect the electrical components of adjacent transmitter units. In other embodiments, the transmitter units are not connected via jumpers. Each transmitter unit also includes a voltage sensor for monitoring the voltage of the attached transmitter coil.

[0009] In each transmitter unit, a first switch and a second switch enable corresponding first and second terminals of the attached transmitter coil to connect to corresponding first and second power transmission lines, and a third switch enables each transmitter unit to be connected in series with the next transmitter unit. Each transmitter unit is connected to a controller via a communication line, enabling the controller to control the first, second, and third switches. In one embodiment, each transmitter unit includes a resonant network of capacitors and inductors and an inverter that provides a synchronous alternating current (AC) waveform to each transmitter unit in a subset of active transmitter units.

[0010] During operation, as the vehicle moves along the path of the embedded transmitter units, the receiver coil receives power from a subset of the active transmitter coils located beneath the vehicle. As the receiver moves in the direction of the leading transmitter unit, the WPT system adds the next subsequent inactive transmitter unit, or "leading" transmitter unit, to the subset of active transmitter units. Simultaneously, the WPT system deactivates the active transmitter unit furthest from the leading transmitter unit within the subset of active transmitter units, i.e., the "last" active transmitter unit. In addition to monitoring the voltage of the leading transmitter unit, the WPT system also monitors the voltage of the first inactive transmitter unit, or "tailing" transmitter unit, following the subset of active transmitter units. The receiver coil is located above the inactive tailing transmitter unit and thus induces a voltage within it; as the receiver coil moves past the tailing transmitter unit, its coverage area decreases, and the voltage within the corresponding transmitter coil decreases. The WTP system activates and deactivates the leading and trailing transmitter units within a subset of active transmitter units based on voltage information from the leading and trailing transmitter units, in order to provide a smooth transition when the subset of active transmitter units changes and minimize oscillations within the system.

[0011] Each of the three switches in each inactive transmitter unit is open, preventing power supply to the coil and preventing the transmitter unit from connecting to adjacent transmitter units. When the prelead transmitter unit is activated, the first switch closes, allowing power to flow through the first end of the attached transmitter coil. The second switch remains open and the third switch closes, preventing power from flowing out of the transmitter coil into the second power transmission line and instead directing power to the next transmitter unit in the subset of active transmitter units. The first switch of the next transmitter unit in series is opened, causing the corresponding transmitter coil to receive power from the newly activated prelead transmitter unit instead of the first power transmission line.

[0012] Within each active transmitter unit between the preamble and trailing transmitter units, the transmitter units connected in series are electrically connected when each third switch is closed. The first and second switches remain open, preventing power from flowing into either the first or second power transmission line. The transmitter coil attached to each transmitter unit between the preamble and trailing transmitter units receives power via jumpers.

[0013] In the last transmitter unit in the series-connected subset of active transmitter units, the first and third switches are open, and the second switch is closed, allowing power to move through the attached transmitter coil to the second power transmission line. The open third switch disconnects the transmitter unit from the next transmitter unit in series (the trailing transmitter unit). In the trailing transmitter unit, each of the three switches is open, similar to all inactive transmitter units, thus preventing power supply to the coil and preventing the transmitter unit from connecting to adjacent transmitter units.

[0014] The long receiver coil partially overlaps with the prelead and tail transmitter units and attempts to induce current in the prelead and tail inactive transmitter units when energized by the adjacent active transmitter. Although the inactive transmitters will not allow current to flow when energized by the receiver coil, they will generate a voltage rise. By monitoring the voltage change between the prelead and tail inactive transmitter units, the WPT system is able to determine the position of the receiver coil relative to the prelead and tail inactive transmitter units.

[0015] If the WPT system detects the same voltage induced in the prelead and tail inactive transmitter units, the receiver is positioned between the prelead and tail inactive transmitter units. If one of the prelead and tail inactive transmitter units has a higher voltage, the receiver coil covers a higher percentage of the transmitter unit with the higher voltage.

[0016] By comparing these voltages over time and observing whether a transmitter voltage increases or decreases, the system can determine the direction of receiver movement. By observing how quickly this change occurs—that is, the rise and fall of voltage over time—the WTP system can determine how fast the receiver is moving.

[0017] Once the receiver's position and orientation are determined, the WTP system identifies the preamble transmitter unit to be activated. WTP enables dynamic wireless power transfer by determining how quickly or when to activate the preamble transmitter unit and how quickly and when to deactivate the last active transmitter unit in a subset of active transmitter units adjacent to the trailing transmitter unit, based on the direction, position, and timing of the receiver coil's movement along the transmitter unit.

[0018] In one embodiment, all third switches in the transmitter unit are closed or replaced with permanent jumpers, and the WPT system uses only the first and second switches to activate and deactivate a subset of the active transmitter units connected in series with the transmitter coils. While this embodiment uses fewer components by eliminating the third switch in each transmitter unit, eliminating the third switch can cause voltage oscillations in all coils, even when no current is flowing through them.

[0019] In one embodiment, the WPT system monitors the voltage difference between the prelead and trailing transmitter units. The controller is pre-programmed with a threshold voltage difference for activating and deactivating the transmitter coils. The controller receives the prelead voltage from the prelead transmitter unit and the trailing voltage from the trailing transmitter unit, and determines the voltage difference. When the absolute value of the voltage difference exceeds the threshold voltage difference, the controller activates the prelead transmitter unit and deactivates the last transmitter unit in a subset of the active transmitter units.

[0020] In some embodiments, the threshold voltage difference is a set value. In other embodiments, the threshold voltage difference is a percentage of the nominal voltage of the active coil.

[0021] The polarity of the voltage difference indicates the direction the vehicle is moving, and which inactive transmitter unit is the leading transmitter unit and which is the trailing transmitter unit among the subset of active transmitter units.

[0022] One object of the present invention is to provide a system for monitoring the use and / or voltage of a transmitter coil and for smoothly activating and deactivating the transmitter coil to minimize disruption to the system.

[0023] The advantage of this invention is that by monitoring the voltage of the transmitter coil, no additional sensors, hardware or other components are required to provide additional control.

[0024] Based on the following detailed description, claims, and drawings, those skilled in the art will recognize additional objects, advantages, and novel features of the solutions provided herein, and / or may learn of additional objects, advantages, and novel features of the solutions provided herein by generating or operating the examples provided herein. Attached Figure Description

[0025] The accompanying drawings illustrate one or more embodiments of the subject matter described herein. They are provided by way of example only. In the drawings, reference numerals are used to denote elements described in the specific embodiments.

[0026] Figure 1 This is a diagram of the wireless power transmission topology of this application.

[0027] Figure 2 yes Figure 1 A schematic diagram of the communication system of the wireless power transmission system.

[0028] Figure 3 yes Figure 2 A schematic diagram of the transmitter interface module of the communication system.

[0029] Figure 4 yes Figure 2 A schematic diagram of a series of transmitter interface modules connected in series in a communication system. Detailed Implementation

[0030] Figures 1 to 4 The illustration depicts a wireless power transfer (WPT) system 100 that utilizes a receiver 102 mounted on a moving vehicle 104. The receiver 102 receives power from a set of transmitter units 106 embedded in a surface 108 on which the vehicle 104 moves. More specifically, the receiver 102 is mounted to the bottom 104A of the vehicle 104, which travels along a rail, track, path, or other route 108 in which the transmitter units 106 are embedded. In track applications, the top surface of the transmitter units 106 is flush with or below the top surface of the track 108. For systems used with rubber-tired vehicles, the transmitters 106 may be on top of or flush with the road surface 108.

[0031] refer to Figure 1Vehicle 104 moves from right to left as indicated by the arrow, and the group of transmitter units 106 includes a subset of active transmitter units 106A located below receiver 102 on vehicle 104 and a set of remaining inactive transmitter units 106B. In the illustrated embodiment, the subset includes seven active transmitter units 106A, although more or fewer active units may exist depending on the system design. During use, as vehicle 104 moves along surface 108, transmitter units 106 are added to and removed from the subset of active transmitter units 106A.

[0032] exist Figure 1 In the sequence, the next transmitter unit 106C to be added to the subset of transmitter units 106A (“precursor” transmitter unit 106C) becomes active as the receiver 102 moves to the left, approaches, and passes over the precursor transmitter unit 106C. The first inactive transmitter unit 106 following the cascaded active transmitter unit 106A subset is the “tail” transmitter unit 106D. The WPT system 100 deactivates the active transmitter unit 106A furthest from the precursor transmitter unit 106C in the subset of active transmitter units 106A (“last” active transmitter unit 106A-f).

[0033] The receiver 102 is longer than a subset of the active transmitter units 106A. In one embodiment, the receiver 102 is approximately 5.5 times the length of a single transmitter unit 106. In one example embodiment, the receiver 102 may be 8 feet long, 33 inches wide, and have a 4-inch ground clearance, while each transmitter unit 106 is approximately 17.5 inches long and 33 inches wide. In this proportion, when the receiver coil 114 is centered on a subset of the active transmitter units 106A, the receiver coil 114 covers 75% of each of the pre-lead transmitter unit 106C and the trailing transmitter unit 106D.

[0034] As receiver 102 continues along the path of embedded transmitter unit 106, receiver 102 transitions to cover 100% of the leading transmitter unit 106C and 50% of the trailing transmitter unit 106D. The activation and deactivation of transmitter coil 106 and the movement of receiver coil 102 can cause power oscillations, and providing a smooth transition coverage of both the leading and trailing inactive transmitter units 106C and 106D prevents or minimizes such oscillations. In other embodiments, different ratios of receiver coil length to subsets of active transmitter unit length are used, and programming methods for detecting and preventing oscillations are employed.

[0035] The WPT system 100 of this application monitors the induced voltages of the lead and trailing transmitter units 106C and 106D to determine the relative position, direction of travel, and speed of the receiver 102 along the ground 108, enabling the system 100 to effectively add and remove transmitter units 106 from a subset of active transmitter units 106A. For example, when more than 60% of the trailing transmitter unit 106D is covered by the receiver 102 and only 10% of the lead transmitter unit 106C is covered, the trailing transmitter unit 106D has a larger voltage that is decreasing, and the lead transmitter unit 106C has a lower voltage that is increasing. The WPT system 100 detects the voltage changes in the lead transmitter unit 106C and the trailing transmitter unit 106D and determines the position of the receiver 102 relative to them.

[0036] An increase in the induced voltage of transmitter unit 106 indicates that receiver 102 is moving toward it. Then, as the subset of active transmitter units 106A changes with the movement of receiver 102, WPT system 100 is able to prepare to activate pre-transmitter unit 106C and simultaneously deactivate the last active transmitter unit 106A-f adjacent to the trailing transmitter unit 106D in the subset of active transmitter units 106A.

[0037] It should be noted that in the WPT system 100 described above, the detection of voltage changes in the transmitter unit 106, the determination of the location of the receiver 102, the activation and deactivation of the transmitter unit 106, and other steps described herein are performed on the controller 110, which includes a memory 113. The controller 110 communicates with a database 112, which can be located within the controller 110, connected to the controller 110 via a wired connection, or accessed remotely via a wireless connection. Programmable instructions on the memory 113 enable the controller 110 to implement programs, processes, or modules that provide the functionality of the WPT system 100 described herein.

[0038] In addition, each transmitter unit 106 includes a voltage sensor 111 as described below. Over time, the WPT system 100 collects data from the voltage sensor 111 of each transmitter unit 106 and populates a database 112, wherein the induced voltage of the transmitter unit 106 is related to the surface area of ​​the transmitter unit 106 covered by the receiver 102. During use, the controller 110 is configured to detect the induced voltages of the lead transmitter unit 106C and the trailing transmitter unit 106D, refer to the database 112 to determine the amount of surface area covered by the receiver 102, and then determine the position of the receiver 102 on the corresponding transmitter unit 106.

[0039] For the preamble transmitter unit 106C, the controller 102 can then determine the remaining range from which the receiver 102 has not yet traveled to cover the preamble transmitter unit 106C, thus preparing the preamble transmitter unit 106C for activation. Similarly, in the case of the trailing transmitter unit 106D, the controller 102 can determine the remaining range from which the receiver 102 has not yet traveled to expose the trailing transmitter unit 106D, thus preparing the last transmitter unit 106A-f in the subset of active transmitter units 106A for deactivation.

[0040] The WPT system 100 is also able to monitor the rate of increase of the induced voltage in order to determine the speed of the receiver 102 on the transmitter unit 106. Using the speed of the receiver 106 and the position of the receiver 102 relative to the preamble transmitter unit 106C and the trailing transmitter unit 106D, the WPT system 100 is able to anticipate when a subset of the active transmitter units 106A will be updated.

[0041] In some embodiments, controller 110 monitors the lead voltage of the transmitter coil 116 of the lead transmitter unit 106C and activates unit 106C when the lead voltage reaches a minimum threshold. Similarly, controller 110 monitors the trailing voltage of the transmitter coil 116 of the trailing transmitter unit 106D and deactivates the last active transmitter unit 106A-f immediately adjacent to the trailing transmitter unit 106D in the subset of active transmitter units 106A when the trailing voltage of the trailing transmitter unit 106D drops below a minimum threshold.

[0042] In another embodiment, when receiver 102 covers a threshold surface area of ​​the preamble and / or trailing transmitter units 106C, 106D, WTP system 100 may activate preamble transmitter unit 106C or deactivate the last active transmitter unit 106A-f in a subset of active transmitter units 106A. For example, when receiver 102 covers less than 25% of the surface area of ​​trailing transmitter unit 106D, or less than 15% in a preferred embodiment, WTP system 100 may deactivate the last active transmitter unit 106A-f. Controller 110 receives the preamble or trailing voltage, refers to a database 112 that associates voltage with surface area coverage to determine the surface area of ​​the preamble or trailing transmitter unit covered by the receiver, and activates or deactivates the appropriate transmitter unit when the surface area is greater than or less than a threshold surface area, respectively.

[0043] In other embodiments, the WPT system 100 monitors the voltage difference between the prelead and trailing transmitter units 106C, 106D. The controller 110 is pre-programmed with a threshold voltage difference for activating and deactivating the transmitter coil 116, or receives this threshold voltage difference from a database 112. The controller 110 receives a prelead voltage from the prelead transmitter unit 106C and a trailing voltage from the trailing transmitter unit 106D, and determines the voltage difference. When the absolute value of the voltage difference is higher than the threshold voltage difference, the controller 110 activates the prelead transmitter unit 106C and deactivates the last transmitter unit 106A-f in the subset of active transmitter units 106A.

[0044] In some embodiments, the threshold voltage difference is a set value. In other embodiments, the threshold voltage difference is a percentage of the nominal voltage of the active coil.

[0045] The polarity of the voltage difference indicates the direction in which the receiver 102 is moving and which of the inactive transmitter units 106C and 106D of the subset adjacent to the active transmitter unit 106A is the pre-transmitter unit 106C and which is the trailing transmitter unit 106D.

[0046] refer to Figures 2 to 4 The transmitter units 106 are connected in series. A subset of the active transmitter units 106A together form a single dummy coil, thus synchronizing the active transmitter units 106A. When transmitter units 106 are added to or removed from the subset, the single dummy coil effectively moves along surface 108, where receiver 102 is mounted to vehicle 102.

[0047] like Figure 2 As shown, receiver 102 includes receiver coil 114 mounted to the bottom of vehicle 104. Resonant tuning network 115 can be used to tune receiver coil 114. Receiver coil 114 is directly or indirectly connected to energy storage system 117, which receives power transmitted from transmitter coil 116 to receiver coil 114. Energy storage system 117 can be a battery, capacitor, mechanical flywheel, or other suitable component or load. Each transmitter coil 116 is mounted to transmitter unit 106, which includes transmitter interface module 118 having electrical components for implementing the operations described herein. Figure 2 The embodiment illustrated shows seven transmitter units 106 connected in series, but the number of transmitter units 106 to be connected in series is not limited.

[0048] The high-frequency power supply 120 is configured to provide at least 20 kHz of high-frequency alternating current (AC) power to the transmitter unit 106 and the corresponding transmitter coil 116 via first and second power transmission lines L1, L2. Direct current (DC) or AC power is supplied to the high-frequency power supply 120. In one embodiment, a laminate constructed similar to a power electronic busbar provides lower resistance than typical wire wiring made of multiple circular conductors.

[0049] In another embodiment, a second power source 120 can supply power to transmitter unit 106, enabling a second subset of active transmitter units to be separate and independently active from the first subset. In this embodiment, the WTP system includes third and fourth power transmission lines L3 and L4 extending in parallel with the first and second power transmission lines L1 and L2. A first and second end of each transmitter coil 116 can be connected to the third power transmission line L3 and the fourth power transmission line L4 using additional switches, serving as a backup for the first power transmission lines L1 and L2. During use, the first subset of active transmitter units 106A receives power from the first transmission line L1 and returns power to the second transmission line L2, as described herein. Elsewhere along the path of the embedded transmitter units, the second subset of active transmitter units 106A receives power from the third transmission line L3 and returns power to the fourth transmission line L4.

[0050] Each transmitter interface module 118 is connected to an adjacent transmitter interface module 118 using jumpers 122, etc. The controller 110 communicates with each transmitter interface module 118 via a communication line 124, which can be daisy-chained through the transmitter interface modules 118 in series, or directly connected from the controller 118 to each transmitter interface module 118. A voltage sensor 111 is located between the first and second ends of a transmitter coil 116, which is connected to the corresponding transmitter interface module 118.

[0051] The transmitter interface module 118 includes a switch for connecting and disconnecting the power transmission lines L1, L2 and jumper 122 between the series-connected transmitter units 106. (Reference) Figure 3 The first and second switches 126 and 128 connect the transmitter coil 116 to power transmission lines L1 and L2, respectively. The third switch 130 connects the jumper wires between adjacent transmitter units 106. Transistors or any mechanical switches can be used for switches 126, 128, and 130.

[0052] Figure 4The diagram illustrates the states of switches 126, 128, and 130 in the subset of active transmitter 106A, the pre-transmitter unit 106C, and the trailing transmitter unit 106D. In the first active transmitter unit 106A-1 of the subset, switch 126A-1 is closed, supplying power from power transmission line L1 to transmitter coil 116A-1. Switches 130A-1, 130A-2, and 130A-3 are closed, allowing transmitter coils 116A-1, 116A-2, 116A-3, and 116A-4 to be connected in series. Switch 128-4 in the last transmitter unit 106A-4 of the subset is closed, connecting coil 116A-4 to power transmission line L2, thus closing the loop.

[0053] All other switches remain open. Switches 126 and 128 of active transmitter units 106A-2 and 106A-3 remain open, allowing power to reach coil 116 of the adjacent transmitter unit 106 via coil 116 and jumper 122. Switch 130 of the last active transmitter unit 106A-4 of the subset is open, thereby preventing power from being transmitted to the trailing transmitter unit 106D.

[0054] In other embodiments, jumpers 122 of all transmitter units 106 remain connected, and no switches are used to connect or disconnect adjacent transmitter units 106. In this case, each coil 116 of a subset of active transmitter units 106 is connected to both the first and second power lines L1, L2. The first and second switches remain open on inactive transmitter unit 106B and are closed when transmitter unit 106A is active.

[0055] It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its accompanying advantages.

Claims

1. A wireless power transfer system for a vehicle including an energy storage system, wherein, The vehicle travels along the surface, and the wireless power transmission system includes: A receiver coil, the receiver coil being mounted to the vehicle, wherein the receiver coil has a length; A plurality of transmitter units electrically connected and positioned on the surface, each transmitter unit associated with an attached transmitter coil, the plurality of transmitter units including inactive transmitter units and a subset of active transmitter units, the inactive transmitter units including a leader transmitter unit and a trailing transmitter unit adjacent to the subset of active transmitter units, wherein the length of the subset of active transmitter units is less than the length of the receiver coil, and wherein each transmitter unit includes a voltage sensor connected to the attached transmitter coil; and A controller that communicates with the voltage sensor of each transmitter unit; A database, which includes data related to the voltage of the transmitter coil; A memory coupled to the controller, wherein the memory stores program instructions executable by the controller, wherein, in response to executing the program instructions, the controller: Receive the prelead voltage of the voltage sensor of the prelead transmitter unit; Receive the tail voltage of the voltage sensor of the tail transmitter unit; The leading voltage of the leading transmitter unit and the trailing voltage of the trailing transmitter unit are compared with data in the database; and Based on the changes in the preamble voltage and the trailing voltage, the position of the receiver relative to the preamble transmitter unit and the trailing transmitter unit is determined. The controller is configured as follows: Store or receive the minimum threshold voltage difference from the database; Calculate the voltage difference between the preamble voltage of the preamble transmitter unit and the tail voltage of the tail transmitter unit; When the voltage difference is greater than the minimum threshold voltage difference, the preamble transmitter unit is activated.

2. The wireless power transmission system according to claim 1, wherein, The subset of the active transmitter units includes the last active transmitter unit adjacent to the trailing transmitter unit, and wherein the controller is configured to deactivate the last active transmitter unit when the voltage difference is greater than the minimum threshold voltage difference.

3. The wireless power transmission system according to claim 1, wherein, The controller is configured to calculate the absolute value of the voltage difference and compare the absolute value with the minimum threshold voltage difference.

4. The wireless power transmission system according to claim 1, wherein, The polarity of the voltage difference indicates the direction the vehicle is traveling.

5. The wireless power transmission system according to claim 1, wherein, Each transmitter coil is connected to a first power transmission line and a second power transmission line. Each transmitter unit is connected in series to an adjacent transmitter unit via a jumper wire. Each transmitter unit includes a first switch and a second switch at the connection points of the first and second ends of the attached transmitter coil with the first power transmission line and the second power transmission line, respectively, and a third switch on the jumper wire. The controller is connected to the first switch, the second switch, and the third switch in each transmitter unit.

6. The wireless power transmission system according to claim 5, wherein, In each inactive transmitter unit, the first switch, the second switch, and the third switch are open; wherein, in each transmitter unit within a subset of the active transmitter units, the third switch is closed.

7. The wireless power transmission system according to claim 6, wherein, In the first transmitter unit of the subset of the active transmitter units, the first switch is closed and the second switch is open; Furthermore, in the last transmitter unit of the subset of active transmitter units, the first switch is open and the second switch is closed.

8. The wireless power transmission system according to claim 7, wherein, The controller is configured to close the first switch and the third switch in the preamble transmitter unit when the voltage difference is greater than the minimum threshold voltage difference.

9. The wireless power transmission system according to claim 7, wherein, The controller is configured to disconnect the second switch and the third switch in the last transmitter unit of the subset of active transmitter units when the voltage difference is greater than the minimum threshold voltage difference.

10. The wireless power transmission system according to claim 1, wherein, Each transmitter coil is connected to a first power transmission line and a second power transmission line, and each transmitter unit includes a first switch and a second switch at the connection points of the first end and the second end of the attached transmitter coil to the first power transmission line and the second power transmission line, respectively, and wherein the controller is connected to the first switch and the second switch in each transmitter unit.

11. The wireless power transmission system according to claim 10, wherein, In each inactive transmitter unit, the first switch and the second switch are open; wherein, in each transmitter unit within a subset of the active transmitter units, the first switch and the second switch are closed.

12. The wireless power transmission system according to claim 11, wherein, The controller is configured to close the first switch and the second switch in the preamble transmitter unit when the voltage difference is greater than the minimum threshold voltage difference.

13. The wireless power transmission system according to claim 11, wherein, The controller is configured to disconnect the first switch and the second switch in the last transmitter unit of the subset of active transmitter units when the voltage difference is greater than the minimum threshold voltage difference.

14. The wireless power transmission system according to claim 1, wherein, The controller is configured to: Store or receive the minimum threshold voltage value from the database; When the preamble voltage of the preamble transmitter unit is greater than the minimum threshold voltage value, the preamble transmitter is activated; as well as When the tail voltage of the tail transmitter unit is less than the minimum threshold voltage value, the tail transmitter unit is deactivated.

15. The wireless power transmission system according to claim 1, wherein, The data in the database includes multiple voltages, each voltage corresponding to the surface area of ​​the transmitter coil covered by the receiver coil, and wherein the controller is configured to: The preamble voltage is compared with the plurality of voltages in the database to determine the surface area of ​​the preamble transmitter unit covered by the receiver coil; and The trailing voltage is compared with the plurality of voltages in the database to determine the surface area of ​​the trailing transmitter unit covered by the receiver coil.

16. The wireless power transmission system according to claim 15, wherein, The controller is configured to: Monitor the voltage rise in the preamble transmitter unit; Monitor the voltage drop in the tail transmitter unit; The speed of the receiver is determined based on the voltage rise and the voltage drop.

17. The wireless power transmission system according to claim 16, wherein, The controller is configured to: Store or receive the minimum threshold voltage value; Determine the amount of time until the preamble voltage of the preamble transmitter unit reaches the minimum threshold voltage value; as well as Determine the amount of time until the tail voltage of the tail transmitter unit reaches the minimum threshold voltage value.

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