System and method for contactless exchange of power

A contactless power transfer system is provided. The contactless power transfer system includes a first power exchanging coil configured to exchange power, a power mating coil operatively coupled to a switching unit, and a controller operatively coupled to the switching unit. The controller is configured to control switching operations of the switching unit to actively control a current in the power mating coil to match an impedance of the first power exchanging coil and enable the exchange of power.

BACKGROUND

Embodiments of the invention generally relate to power transfer systems and, more particularly, to systems for contactless exchange of power.

Power transfer systems are employed for transmitting power from one object to another. Based on a method of transmitting power, the power transfer systems may be classified into power transfer systems using physical connections between a transmitter and a receiver for transmitting power and systems for contactless exchange of power in which there is no physical connection between the transmitter and the receiver.

The systems for contactless exchange of power may employ various methods for transmitting power wirelessly. One such approach may include an inductive coupling system that may further include a transmitter coil and a receiver coil. In this approach, both the transmitter coil and the receiver coil may be inductively coupled to a respective transformer winding and may transmit power based on inductive coupling.

In an alternative approach, a resonator based system for contactless exchange of power may be used. One such resonator based system may include a three coil system. The three coil system may include a transmitter coil, a receiver coil and a resonator for enhancing a resonance coupling between the transmitter coil and the receiver coil. In another approach multiple resonators may also be used for contactless exchange of power.

Although all the aforementioned approaches exchange power using a contactless medium, none of the approaches provide a flexibility of using the transmitter coil and/or the receiver coil with different specifications. In certain applications such as EV charging, the transmitter coil or the charging station may have one set of specifications which may not be compatible with the receiver coil in a vehicle. Such incompatibility issues between the transmitter coil and the receiver coil may create undesirable restrictions for a consumer which need to be addressed using an improved system.

BRIEF DESCRIPTION

Briefly, in accordance with one embodiment, a contactless power transfer system is provided. The contactless power transfer system includes a first power exchanging coil configured for contactless exchange of power, a power mating coil operatively coupled to a switching unit, and a controller operatively coupled to the switching unit. The controller is configured to control switching operations of the switching unit to actively control a magnitude and a phase of current in the power mating coil to match an impedance of the first power exchanging coil and enable a contactless exchange of power.

In another embodiment, a system for contactless exchange of power is provided. The system includes a contactless power transfer system that includes a first power exchanging coil configured for contactless exchange of power, a power mating coil operatively coupled to a switching unit, and a controller operatively coupled to the switching unit. The controller is configured to control switching operations of the switching unit to actively control a magnitude and a phase of current in the power mating coil to match an impedance of the first power exchanging coil and enable a contactless exchange of power. The system also includes a second power exchanging coil operatively coupled to the contactless power transfer system and configured to exchange power with the first power exchanging coil via a magnetic field.

In yet another embodiment, a method for contactless exchange of power is provided. The method includes operatively coupling a first power exchanging coil having first impedance and a second power exchanging coil having a second impedance. The method also includes operatively coupling the first power exchanging coil to a power mating coil. The method further includes actively controlling a magnitude and a phase of current in the power mating coil to modify the first impedance of the first power exchanging coil to match the second impedance of the second power exchanging coil and enable contactless exchange of power between the first power exchanging coil and the second power exchanging coil.

DETAILED DESCRIPTION

Embodiments of the present invention include system and a method for contactless exchange of power. The system includes a contactless power transfer system that further includes a first power exchanging coil configured for contactless exchange of power, a power mating coil operatively coupled to a switching unit, and a controller operatively coupled to the switching unit. The controller is configured to control switching operations of the switching unit to actively control a magnitude and a phase of current in the power mating coil to match an impedance of the first power exchanging coil and enable a contactless exchange of power. The system also includes a second power exchanging coil operatively coupled to the contactless power transfer system and configured for contactless exchange of power with the first power exchanging coil via a magnetic field.

Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms “first”, “second”, and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. The term “or” is meant to be inclusive and mean one, some, or all of the listed items. The use of “including,” “comprising” or “having” and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Specifically, unless indicated otherwise, the term “coupled” includes resonance coupling that is defined as a coupling between two or more resonators such that they are able to exchange power when excited at a particular frequency. The terms “exchange” and “transfer” may be used interchangeably in the specification and convey the same meaning. Unless specified otherwise, the term “exchange” may be defined as a contactless exchange of power for the purposes of this specification.

FIG. 1is a schematic representation of a contactless power transfer system100in accordance with an embodiment of the invention. The contactless power transfer system100includes a first power exchanging coil110configured to exchange power. The first power exchanging coil110is operatively coupled to a load120which receives power from the first power exchanging coil110. The first power exchanging coil110is magnetically coupled to a power mating coil130. The power mating coil130is operatively coupled to a switching unit140. In one embodiment, the switching unit140may include an insulated gate bipolar transistor (IGBT), a silicon controlled rectifier (SCR), a metal-oxide semiconductor field effect transistor (MOSFET), or a mechanical switch. The switching unit140is employed to vary a magnitude and a phase of current in the power mating coil130for matching an impedance of the first power exchanging coil110. To this end, the switching unit140is operatively coupled to a controller150that controls switching operations of the switching unit140. The controller150actively controls the magnitude and the phase of current in the power mating coil130to match the impedance of the first power exchanging coil110, which further enables the exchange of power. Further details of active control of the magnitude and the phase of current by the controller150are discussed later in the specification. Hereinafter, the term “active control” may be defined as a control scheme which uses an external gate pulse to transition the switching unit140between a conducting state and a non-conducting state. Such external gate pulses may be provided by the controller150to the switching unit140for varying the magnitude and the phase of current in the power mating coil130and matching the impedance of the first power exchanging coil110.

Referring toFIG. 2, the contactless power transfer system100may be operatively coupled to a second power exchanging coil160to form a system for contactless exchange of power200as depicted inFIG. 2. The second power exchanging coil160is operatively coupled to a coil capacitor170and may include an internal resistance depicted by resistance180. The first power exchanging coil110in the contactless power transfer system100exchanges power with the second power exchanging coil160via a magnetic field190. In an exemplary embodiment, the second power exchanging coil160may be configured to operate as a transmitter coil and the first power exchanging coil110may be configured to operate as a receiver coil. However, any one of the first power exchanging coil110or the second power exchanging coil160may be configured to operate as the transmitter coil or the receiver coil in different embodiments based on system requirements. In some embodiments, power exchanging coils110and160may act as both transmitter and receiver simultaneously allowing for simultaneous bidirectional exchange of power. For example, the contactless power transfer system100may be provided at a transmitter end210in the system200. In such a configuration, the first power exchanging coil110may transmit power to the second power exchanging coil160. Similarly, the contactless power transfer system100may also be provided at a receiver end220in the system200and the first power exchanging coil110may be configured to receive power from the second power exchanging coil160. In one embodiment, a field focusing element (FIG. 3) may be added to the system200for contactless exchange of power to enhance coupling between the first power exchanging coil110and the second power exchanging coil160. In another embodiment, one or more repeater resonators (not shown) may be added to the system200for contactless exchange of power to increase a predetermined distance (FIG. 3) between the first power exchanging coil110and the second power exchanging coil160. In some embodiments, the system200for contactless exchange of power may include the field focusing element, the one or more repeater resonators, or a combination thereof. In another embodiment, the field focusing element, the one or more repeater resonators or both may be placed at the transmitter end210, the receiver end220or a combination thereof For better understanding, an embodiment where the contactless power transfer system100is provided at the receiver end220in the system200for exchanging power is discussed.

In a specific embodiment, and with continued reference toFIG. 2, the second power exchanging coil160may be electrically coupled to a power source230and the first power exchanging coil110may be electrically coupled to the load120. In an exemplary embodiment, the load120may include an energy storage device. The second power exchanging coil160receives power from the power source230and converts the power into the magnetic field190. The power is transmitted to the contactless power transfer system100via the magnetic field190. As disclosed above, the contactless power transfer system100includes the power mating coil130to match impedance of the first power exchanging coil110to enable exchange of power between the first power exchanging coil110and the second power exchanging coil160. In one embodiment, the first power exchanging coil110may operate at a first operating frequency and the power mating coil130may operate at a second operating frequency, where the first operating frequency is different from the second operating frequency.

Initially, during operation, the contactless power transfer system100and the second power exchanging coil160are placed within a predetermined distance240such that a distance between the first power exchanging coil110and the second power exchanging coil160does not exceed the predetermined distance240. It may be noted that the first power exchanging coil110and the second power exchanging coil160may not be compatible with each other and may be unable to exchange power. Such incompatibility between the first power exchanging coil110and the second power exchanging coil160may be observed due to different specifications of the first power exchanging coil110and the second power exchanging coil160. In one embodiment, the specifications may include an operating frequency of the first power exchanging coil110and the second power exchanging coil160, difference in a coil design of the first power exchanging coil110and the second power exchanging coil160, impedance of the first power exchanging coil110and the second power exchanging coil160, or any other parameter that may affect magnetic coupling between two power exchanging coils. Therefore, in order to overcome the incompatibility between the first power exchanging coil110and the second power exchanging coil160, the magnitude and the phase of the current in the power mating coil130is actively controlled by the controller150to match the impedance of the first power exchanging coil110with the impedance of the second power exchanging coil160.

To this end, the controller150performs a frequency sweep to identify a duty cycle of the switching unit140that may enable the exchange of power between the first power exchanging coil110and the second power exchanging coil160. In one embodiment, the frequency sweep may be performed based on a hit and trial method with predetermined duty cycles. In another embodiment, the predetermined duty cycles of the switching unit140may be stored in a controller memory (not shown). The predetermined duty cycles may represent different operating frequencies of the switching unit140which in turn represent the operating frequencies of the power mating coil130. The different operating frequencies of the power mating coil130result in different impedances of the first power exchanging coil110that may match with impedances of different second power exchanging coil configurations currently available. In one embodiment, the second power exchanging coil configurations may be updated in the controller150at predefined time intervals to provide compatibility and interoperability with maximum number of different second power exchanging coil configurations.

While performing the frequency sweep, the controller150executes each duty cycle to provide gate pulses to the switching unit140based on the duty cycle. The gate pulses enable the transition of the switching unit140between the conducting state and the non-conducting state. Such transitions actively control the magnitude and the phase of the current in the power mating coil130. Consequently, since the power mating coil130is magnetically coupled to the first power exchanging coil110, the variation in the magnitude and the phase of the current leads to a change in impedance of the first power exchanging coil110. This change in the impedance of the first power exchanging coil110is used to match the impedance of the second power exchanging coil160.

Furthermore, due to placement of the second power exchanging coil160within the predetermined distance240as discussed above, the second power exchanging coil160magnetically couples to the first power exchanging coil110when the impedance of the first power exchanging coil110is matched with the second power exchanging coil160and an exchange of power may initiate. The controller150uses this principle to identify the duty cycle that matches the impedance of the first power exchanging coil110with the impedance of the second power exchanging coil160. In one embodiment, the controller150may obtain power exchange data (not shown) from the first power exchanging coil110and the second power exchanging coil160to determine if the duty cycle executed by the controller150matches the impedance of the first power exchanging coil110with the impedance of the second power exchanging coil160. Similarly, the controller150executes each duty cycle until the controller150identifies the duty cycle that matches the impedance of the first power exchanging coil110with the impedance of the second power exchanging coil160. In one embodiment, the controller150may execute each duty cycle sequentially or randomly. Furthermore, upon identifying the duty cycle that matches the impedance of the first power exchanging coil110with the second power exchanging coil160, the controller150continues with the same duty cycle until exchange of power is completed. In another embodiment, the controller150may modify the identified duty cycle based on a change in power being exchanged, or a temperature of one or more coils in the system for contactless exchange of power200while exchanging power to maintain optimal efficiency and power transfer capabilities.

FIG. 3is a schematic representation of a system250for contactless exchange of power with a contactless power transfer system260including a field focusing element270operatively coupled to the first power exchanging coil110in accordance with an embodiment of the invention. The field focusing element270enhances magnetic coupling between the first power exchanging coil110and the second power exchanging coil160. In one embodiment, the field focusing element270may be placed between the first power exchanging coil110and the second power exchanging coil160. In another embodiment, the field focusing element270may focus the magnetic field190transmitted by the second power exchanging coil160to the first power exchanging coil110or transmitted from the first power exchanging coil110onto the second power exchanging coil160. In a specific embodiment, the field focusing element270may include at least one resonator and the at least one resonator may be configured to enable a bi-directional transfer of power and data signals between the first power exchanging coil110and a second power exchanging coil160.

FIG. 4depicts various structures of the at least one resonator that may form the field focusing element270in the contactless power transfer system260ofFIG. 3. In one embodiment, the field focusing element270may include a single loop coil280. In another embodiment, the field focusing element270may include multiple turns such as in a split ring structure290, spiral structure300, Swiss-roll structure310, or helical coil320. Selection of a structure for a particular application is determined by the size and self-resonating frequency of the field focusing element270.

Referring back toFIG. 3, in one embodiment, ends272,274(FIG. 4) of the field focusing element270may be coupled to a field focusing capacitor330that forms a capacitively loaded coil as represented inFIG. 3. Such a capacitively loaded coil upon excitation, amplifies the magnetic field190received from the second power exchanging coil160and transmits an amplified magnetic field (not shown) to the first power exchanging coil110.

In another embodiment, the ends272,274of the field focusing element270may be left open and the field focusing capacitor330may not be coupled to the ends272,274of the field focusing element270. In such an embodiment, the field focusing element270behaves as a self-resonant coil and when the second power exchanging coil is excited at a resonant frequency of the field focusing element270, a standing wave current distribution may be developed within the field focusing element270between the ends272,274of the field focusing element270. The standing wave current distribution may lead to a non-uniform magnetic field distribution around the field focusing element270. Such non-uniform current distribution may be configured to focus the magnetic field190in any desired direction, such as, in a direction of the first power exchanging coil110in this example. When operating at resonant frequency, even a small excitation of the field focusing element270produces large amplitude of current distribution along the length of the field focusing element270. Large current magnitude of non-uniform distribution may lead to an amplified and focused magnetic field in the direction of the first power exchanging coil110that results in higher efficiency of power transfer. Greater details of the operation of the field-focusing element270are described in commonly assigned U.S. Pat. No. 8674550, issued on Mar. 18, 2014 which is hereby incorporated by reference in its entirety.

Furthermore,FIG. 5depicts a schematic representation of an exemplary embodiment of the field focusing element270that may include a plurality of resonators340arranged in an array350and the plurality of resonators340focus a resultant magnetic field of the plurality of resonators340towards a direction of the first power exchanging coil110or the second power exchanging coil160. More specifically, the plurality of resonators340arranged in the array350are configured to operate as a single unit where a resultant magnetic field (not shown) is established by the respective magnetic fields of the plurality of resonators340in the array350by interfering constructively (adding) in a desired direction to achieve magnetic field focusing and interfering destructively (canceling each other) in the remaining space. Although, one form of the array350is shown, there may be various other forms of array that can be implemented using the plurality of resonators340. In a specific embodiment, other forms of array may include a two dimensional array or a three dimensional array. The resultant magnetic field may be transmitted to the first power exchanging coil110or the second power exchanging coil160based on the configuration of the system250. Moreover, in a particular embodiment, the plurality of resonators340may be configured to operate at two or more different resonance frequencies simultaneously to enable a simultaneous bi-directional transfer of power and data signals between the first power exchanging coil110and the second power exchanging coil160.

With continued reference toFIG. 3, in addition to matching the impedance of the first power exchanging coil110with the impedance of the second power exchanging coil160, the power mating coil130may also compensate for the change in phase resulting from any misalignment of the contactless power transfer system260with respect to the second power exchanging coil160, change in the load120at the first power exchanging coil110, drift in characteristics such as inductance and capacitance of the first power exchanging coil110, the second power exchanging coil160, the power mating coil130and the field focusing element270due to ageing and environmental effects such as deposition of mud, ice water. As used herein, the term “misalignment” means any angular deviation between the second power exchanging coil (e.g., second power exchanging coil160) and the contactless power transfer system (e.g., contactless power transfer system260). Notably, the field focusing element270, the first power exchanging coil110and the power mating coil130are coupled to each other in a relatively fixed position and form the contactless power transfer system260. Any misalignment in the system250would be between the contactless power transfer system260and the second power exchanging coil160and should not be interpreted as a misalignment between the individual components of the contactless power system260. In an exemplary embodiment, the first power exchanging coil110may be operatively coupled between the field focusing element270and the power mating coil130. In one embodiment, the power mating coil130and the field focusing element270, each operate at different resonant frequencies with respect to each other. In another embodiment, the resonant frequency of the power mating coil130is higher than the resonant frequency of the field focusing element270. This provides a capacitive reactance to the contactless power transfer system260and compensates for a lagging power factor in the system250. In one example, the power mating coil130operates at twice the frequency of the first power exchanging coil110. In another embodiment, the resonant frequency of the power mating coil130is lower than the resonant frequency of the field focusing element270. This provides an inductive reactance to the contactless power transfer system260and compensates for a leading power factor in the system250. In an exemplary embodiment, the resonant frequency of the field focusing element270is equal to the resonant frequency of the second power exchanging coil160and therefore, by extension, the resonant frequency of the power mating coil130is different from the resonant frequency of the second power exchanging coil160.

During operation, the power mating coil130behaves as a capacitor due to the relatively higher resonant frequency as compared to the field focusing element270and provides capacitive reactance to the system250that increases efficiency and power transfer capabilities of the system250. The efficiency of the system250depends on the input power factor of the system250and the efficiency of the system250is enhanced by increasing the input power factor of the system250. The capacitive reactance provided by the power mating coil130results in impedance matching and reduces the current drawn by the system250for transmitting power to the load120and hence improves the input power factor of the system250resulting in enhanced efficiency.

Moreover, the capacitive reactance provided by the power mating coil130increases the power transfer capability of the system250by increasing a power output of the system250. The power output at the load120depends on a total reflected impedance of the system250. The capacitive reactance provided by the power mating coil130reduces the total reflected impedance, which in turn increases the power transfer capability of the system250. Due to the enhanced efficiency and the power transfer capability of the system250, the second power exchanging coil160and the contactless power transfer system260are said to have enhanced coupling between each other.

FIG. 6is a schematic representation of another embodiment400of the system for contactless exchange of power ofFIG. 3in accordance with an embodiment of the invention. In this embodiment, the system400includes a contactless power transfer system410and a second power exchanging coil420. The contactless power transfer system410includes a first integrated coil430and a first power exchanging coil440. The first integrated coil430includes a field focusing element and a power mating coil electrically coupled to each other. The field focusing element and the power mating coil share a common capacitor450which generally has a capacitance higher than that of the capacitors used inFIG. 3. The common capacitor approach helps in reducing costs and losses when compared to the system ofFIG. 3. Furthermore, the first integrated coil430also includes a switching unit460operatively coupled to the common capacitor450. The switching unit460is operatively coupled to a controller470. The second power exchanging coil420generates a magnetic field480from the power received from a power source490and transmits the magnetic field480to the contactless power transfer system410. Further details of the operation of system can be referred from the above mentioned description of system ofFIG. 3.

FIG. 7is a schematic representation of yet another embodiment500of the system for contactless exchange of power ofFIG. 3in accordance with an embodiment of the invention. The present embodiment500includes a contactless power transfer system510and a second power exchanging coil520. The contactless power transfer system510includes a second integrated coil530. The second integrated coil530includes a field focusing element, a power mating coil and a first power exchanging coil electrically coupled to each other to form the second integrated coil530where the power mating coil is electrically coupled to the field focusing element between the field focusing element and the first power exchanging coil. Furthermore, the second integrated coil530also includes a switching unit540operatively coupled to a common capacitor550. The switching unit540is further coupled to a controller560that controls switching operations of the switching unit to actively control the magnitude and the phase of the current in the second integrated coil530. Generally, the power at the output (not shown) of the first power exchanging coil is calculated by determining a difference between power received by the first power exchanging coil and the total internal losses of the first power exchanging coil. One such component of the total internal losses may include self-inductance losses. In the present embodiment, the self-inductance losses are canceled by the capacitive reactance provided by the power mating coil resulting in higher power at a load570coupled to the second integrated coil530as compared to the conventional system (not shown). Furthermore, the present embodiment enables the second integrated coil530to share the one capacitor, establish resonance between the first power exchanging coil and the field focusing element, match impedance of the first power exchanging coil with the impedance of the second power exchanging coil, and reduce the self-induction losses in the first power exchanging coil. Further details of the operation of system may be referred from the above mentioned description of system ofFIG. 3.

FIG. 8is a schematic representation of a system600for contactless exchange of power including a plurality of first power exchanging coil610and a plurality of power mating coils620in accordance with an embodiment of the invention. Each of the plurality of first power exchanging coils610is operatively coupled to a corresponding power mating coil620. Moreover, a plurality of switching units630may be operatively coupled to the plurality of power mating coils620. The plurality of power mating coils may be operatively coupled to a controller640and the controller640may individually control the plurality of switching units630to selectively enable power exchange between one or more first power exchanging coils610and one or more second power exchanging coils650. For example, the system600may include four first power exchanging coils represented by reference numerals612-618. Each of the four first power exchanging coils612-618may be individually coupled to four corresponding power mating coils622-628. Each of the four power mating coils612-618may include a corresponding switching unit632-638which may be operatively coupled to the controller640. For illustration purposes, only one second power exchanging coil650is represented, however multiple second power exchanging coils650may also be used to simultaneously exchange power with the one or more first power exchanging coils610.

During operation, upon placing the second power exchanging coil650within a predetermined distance660from the plurality of first power exchanging coils610, the controller640detects the presence of the second power exchanging coil650and selects the one or more corresponding first power exchanging coils614,616that may need to be enabled to exchange power with the second power exchanging coil650. In one embodiment, the controller640may detect the presence of the second power exchanging coil650based on load detection algorithms that determine variations in an impedance of the plurality of first power exchanging coils during a presence or an absence of the second power exchanging coil650in the system600for contactless exchange of power. Subsequently, the controller640controls the switching units634,636of the corresponding power mating coils624,626to actively control a magnitude and a phase of current in the corresponding power mating coils624,626. The active control of the magnitude and the phase of current in the corresponding power mating coils624,626matches the impedance of only the one or more selected first power exchanging coils614,616that were selected by the controller640with the second power exchanging coil650. This enables the exchange of power between one or more selected first power exchanging coil614,616and the second power exchanging coil650.

FIG. 9is a schematic representation of an exemplary electric vehicle charging system700including a contactless power transfer system710electrically coupled to an electric vehicle720for charging the electric vehicle720and a charging station730electrically coupled to a second power exchanging coil740in accordance with an embodiment of the invention. The contactless power transfer system710further includes a first power exchanging coil (FIG. 1), a power mating coil (FIG. 1) and a controller (FIG. 1) where the first power exchanging coil may have a first impedance. Furthermore, the charging station730is electrically coupled to a power source750and the second power exchanging coil740, where the second power exchanging coil740may have a second impedance. The charging station730further includes a designated parking area760with the second power exchanging coil740disposed within the designated parking area760.

In an exemplary effort to charge the electric vehicle720, the electric vehicle720may be parked in the designated parking area760such that a distance between the contactless power transfer system710and the second power exchanging coil740is within a predetermined distance. However, the first impedance of the first power exchanging coil in the contactless power transfer system710may be different from the second impedance of the second power exchanging coil740which may lead to incompatibility issues. Therefore, the power mating coil in the contactless power transfer system710may modify the first impedance of the first power exchanging coil to match the second impedance of the second power exchanging coil740. To this end, the controller in the contactless power transfer system710determines a duty cycle of a switching unit operatively coupled to the power mating coil and controls switching operations of the switching unit based on the determined duty cycle. Moreover, by controlling the switching operations of the switching unit, the controller actively controls a magnitude and a phase of the current in the power mating coil which in turn modifies the first impedance of the first power exchanging coil to match with the second impedance of the second power exchanging coil740.

Upon matching the first impedance of the first power exchanging coil with the second impedance of the second power exchanging coil740, the second power exchanging coil740initiates exchange of power by transmitting a magnetic field770to the first power exchanging coil. The magnetic field770is generated from power received by the second power exchanging coil740from the power source750. The first power exchanging coil receives the magnetic field770and converts the magnetic field770to power that is further transmitted to an energy storage device780electrically coupled to the contactless power transfer system710. In one embodiment, the energy storage device780may include a battery which may be used to operate the electric vehicle720. In another embodiment, the first power exchanging coil may simultaneously exchange data with the second power exchanging coil740. In one embodiment, the data may include charging data.

In one embodiment, a field focusing element (FIG. 3) may also be disposed between the first power exchanging coil and the second power exchanging coil740. In one embodiment, the field focusing element may be disposed in the electric vehicle720or in the charging station730independent of a location of contactless power transfer system710. The field focusing element may receive the magnetic field770from the second power exchanging coil740and may focus a received magnetic field in a direction of the first power exchanging coil or vice versa to further enhance the efficiency of the exchange of power between the contactless power transfer system710and the second power exchanging coil740. In an exemplary embodiment, the field focusing element enables simultaneous bi-directional exchange of power, data, or both.

FIG. 10is a schematic representation of an alternative embodiment800of the electric vehicle charging system ofFIG. 9in accordance with an embodiment of the invention. In this embodiment, the contactless power transfer system710may be disposed in the designated parking area760and the first power exchanging coil in the contactless power transfer system710may be electrically coupled to the power source750in the charging station730. Furthermore, the second power exchanging coil740may be disposed in the electric vehicle720and may be electrically coupled to the energy storage device780. However, the operations of the electrical vehicle charging system may remain the same with respect to the operations discussed inFIG. 9. In addition, the second power exchanging coil740may also simultaneously exchange data related to the energy storage device780with the charging station730via the magnetic field770. In one embodiment, the data may include charging data.

FIG. 11is a flow chart representing steps involved in a method900for contactless exchange of power in accordance with an embodiment of the invention. The method900includes operatively coupling a first power exchanging coil having a first impedance and a second power exchanging coil having a second impedance in step910. Furthermore, the first power exchanging coil may be operatively coupled to a power mating coil in step920. The method900may further include actively controlling a magnitude and a phase of current in the power mating coil to modify the first impedance of the first power exchanging coil to match the second impedance of the second power exchanging coil to enable exchange of power between the first power exchanging coil and the second power exchanging coil in step930. In one embodiment, a frequency sweep may be performed between the first power exchanging coil, the second power exchanging coil and the power mating coil. The frequency sweep determines a duty cycle of a switching unit to modify the first impedance to match the second impedance of the second power exchanging coil and enable the exchange of power between the first power exchanging coil and the second power exchanging coil. In another embodiment, a plurality of first power exchanging coil and a plurality of power mating coils may be provided. Each of the first power exchanging coil may be operatively coupled to corresponding power mating coil, where the current in each of the power mating coils may be individually controlled to match the impedance of the one or more first power exchanging coils with the second impedance of the second power exchanging coils to enable exchange of power between one or more first power exchanging coils and the second power exchanging coil.

It is to be understood that a skilled artisan will recognize the interchangeability of various features from different embodiments and that the various features described, as well as other known equivalents for each feature, may be mixed and matched by one of ordinary skill in this art to construct additional systems and techniques in accordance with principles of this disclosure. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.