Patent Description:
Wireless power transfer is used to charge various different loads such as batteries. Some known wireless power transfer systems use a single phase coil system in at least the transmitter. Single phase designs work by pulsing the flux produced by the primary coil with time. Part of this time-varying flux couples with the secondary coil and induces a voltage. The induced voltage causes a current to flow, transferring power to the load. However, power transfer and time needed are limited by certain design constraints in a single phase system. For example, in a single phase system, power transfer capabilities are limited by electromagnetic field emissions requirements and foreign object heating (touch safety) limits, the size and mass of the transmitting and receiving coil assemblies.

There is a push to higher power charging and a quicker charging timing. For example, a goal is to provide a charging rate for an electric vehicle on parity with a traditional vehicle refueling time. The feasibility of high-power wireless power transfer greatly depends on the ability to improve the power density and specific power of wireless charging systems.

Certain polyphase wireless transfer systems have been designed to increase power transfer for electric vehicles, however, since there is a non-zero interphase mutual-inductance, which may be unbalance between phases, power transfer capability may be compromised and reduced for these systems.

<CIT> discloses a polyphase inductive power transfer system apparatus for inductively coupled electric vehicle charging systems. The apparatus has a magnetic coupling coil associated with each phase and a compensation network associated with each magnetic coupling coil for providing power to or receiving power from the respective coil. At least one of the compensation networks is provided with a different power transfer characteristic to the other compensation networks. The compensation network is provided with a first power transfer characteristic and multiple other compensation networks with a second power transfer characteristic. The magnetic coupling coils are magnetically and/or electrically coupled.

The invention is defined by a three-phase inductive power transfer system with the technical features of independent claim <NUM>. Advantageous embodiments are depicted in the dependent claims, which gather further aspects of the invention.

In some aspects of the disclosure, the phases may bipolar. In other aspects, the phases may be unipolar. When the phases are bipolar, each phase has two coils of opposite polarities.

In some aspects of the disclosure, the coils are layered in a coil assembly. The coil assembly may comprise one or more layers of coils stacked on a ferrite. In some aspects, coils for different phases are located on different layers. In other aspects, coils having different polarities are located on different layers. For example, coils having the same polarity are one layer and coils having an opposite polarity are a second layer.

In some aspects of the disclosure, the coil assembly comprises a housing. The ferrite and the layers may be disposed in the housing. The coils may be positioned using one or more wireguides and may be secured in place using a thermal epoxy.

In some aspects of the disclosure, the connections to the compensating capacitance are co-planar with the coils.

In some aspects of the disclosure, the topology may be one of a series delta-capacitance-delta inductance, a series wye-capacitance-delta inductance, a series delta-capacitance-wye inductance or a series wye-capacitance-wye inductance. In other aspects, the system may also comprise a compensating network. The compensating network may have an LCC configuration.

In some aspects of the disclosure, the system further comprises a receiver having at least one coil per phase. The receiver also has a compensating capacitance connected in series with the at least one coil for each phase. The value of the compensating capacitance determined, for each phase, such that the receiver has at least two independently excitable resonant modes at the resonant frequency.

Also disclosed are polyphase coil assemblies. The polyphase coil assemblies may be bipolar. For example, in some aspects of the disclosure, the coil assembly may comprise a ferrite and two coils for each of the polyphases. The two coils have opposite polarity. The assembly may be a single layer. In this aspect, the coil for different phases are interleaved where coils of opposite polarity are on opposite sides of the layer. The distance between each coil and the ferrite is the same. In some aspects, all connections to a compensation network are co-planar with the coils.

In other aspects, the coil assemblies may be multiple layers. For example, the assembly may comprise layers where coils for the same phase are on the same layer where coils for the different phases have a different distance to the ferrite.

In other aspects, disclosed is a double layer coil assembly. The double layer coil assembly may comprise a ferrite and two coils for each of the phases. Coils for the same phases are located on different layers where the coils having the same polarity are located on the same layer. Coils for the same phase that have opposite polarity are not aligned in a stacked direction, and the distance between the ferrite and each layer is different. In an aspect, when there are three-phases, each coil spans <NUM>° of a respective layer.

In an aspect, the ferrite may be formed by ferrite tiles.

In an aspect, the phases may have a balanced self and mutual inductance.

Also disclosed is a polyphase wireless power transfer system where the transmitter may transfer power to different types of receivers. The system may comprises a transmitter having at least one coil associated with each phase, a compensating network connected with the at least one coil for each phase, an inverter and a controller. The inverter may comprise a plurality of switching pairs. Each switching pair respectively electrically coupled to the compensating network and the at least one coil for a respective phase. The controller may be electrically coupled to each of the plurality of switching pairs to selectively turn OFF or ON a respective switch. In some aspects of the disclosure, the timing in which each of the switching pairs is turned OFF or ON is based on a type of receiver being inductively coupled to the transmitter.

In some aspects of the disclosure, the system further comprises a wireless interface. The receiver may transmit its type to the transmitter. In transmitter may receive the type via the wireless interface. The controller may control the timing based on the received type of receiver.

In other aspects of the disclosure, the controller detects the type of receiver. For example, the system may further comprise a memory configured to store electrical properties associated with the types of receiver. The controller may be configured with a test mode. In the test mode, the controller may control the switching pairs to sequentially excite a plurality of excitable resonant modes for a set time. For each of the excitable resonant modes, the controller may receive sensed electrical properties. The controller may comprise the sensed electrical properties with the stored electrical properties and determine a match. When there is a match, the type of receiver associated with the matched electrical properties may be determined as the receiver. In some aspects of the disclosure, the controller controls the timing based on the detected type of receiver.

In other aspects of the disclosure, the system may further comprise a camera. The camera may detect an alignment condition between the coil(s) in the transmitter and the coil(s) in the receiver. The alignment condition may include translational and rotational alignment. In some aspects of the disclosure, the controller may control the timing based on the detected alignment condition by the camera.

In other aspects of the disclosure, the controller detects the alignment condition. In this aspect, the system may further comprise memory configured to store electrical properties associated with the a plurality of translational and rotational alignment conditions for each type of receiver, Further, in this aspect, the controller may comprise the sensed electrical properties in the test mode for each of the plurality of excitable resonant modes with the stored electrical properties associated with the a plurality of translational and rotational alignment conditions for each type of receiver. When there is a match, the alignment condition(s) associated with the matched electrical properties may be determined as the alignment condition(s). In some aspects of the disclosure, the controller controls the timing based on the detected alignment condition(s).

In other aspects of the disclosure, the wireless interface may receive an alignment condition from the receiver and the controller may control the timing based on the received alignment condition.

In some aspects, each phase may be unipolar and the inverter may comprise another switching pair. The another switching pair is electrically coupled to a neutral of the coil for each phase. In this aspect, the controller is electrically coupled to the another switching pair to selectively turn OFF or ON a respective switch. The another switching pair is controlled based on a type of receiver being inductively coupled to the transmitter.

In some aspects of the disclosure, the receiver may be a three-phase receiver or a single phase receiver. The single phase receiver may be unipolar, such as, having circular receiving or a bipolar receiver, such as, having a DD receiving coil.

When the receiver is a three-phase receiver, the controller may maintain the another switching pair OFF or turn the another switching pair OFF and control the switching of three switching pairs at a different timing.

When the receiver is a single phase bipolar receiver, the controller may maintain the another switching pair OFF or turn the another switching pair OFF and control the switching of two switching pairs of the plurality of switching pairs at the same time when rotationally aligned and a third switching pair of the plurality of switching pairs at a different timing.

When the receiver is a single phase unipolar receiver, the controller may control the switching of three switching pairs of the plurality of switching pairs corresponding to three-phases at the same time when aligned and control the another switching pair to turn ON and OFF. The another switching pair may be used to control the duty cycle.

When transmitter is bipolar, the receiver may be a three-phase receiver or a single phase bipolar receiver. The timing may be the same as when the transmitter is unipolar.

In other aspects of the disclosure, when the transmitter is bipolar, different switching pairs may be electrically coupled to the different polarity. For example, the plurality of switching pairs may comprise a plurality of first switching pairs and plurality of second switching pairs, where the first switching pairs and the second switching pairs may be electrical coupled to coils of different polarity, respectively. In this aspect, the inverter may further comprise two other switching pairs, one switching pair of the other switching pairs may be electrically coupled to neutral of coils of a first polarity for each phase and the second switching pair of the other switching pairs may be electrically coupled to the neutral of coils of the opposite polarity. In this aspect, the receiver may be a three-phase receiver or a single phase receiver that is either unipolar or bipolar.

When the type of receiver is the three-phase receiver, the controller may maintain the each of the two other switching pairs OFF or turn each of the two other switching pairs OFF and control the switching of the plurality of first switching pairs and the plurality of second switching pairs such that switching pairs coupled to coils of opposite polarities of the same phase are controlled at the same time and switching pairs coupled to coils of different phases are controlled at different times.

When the type of receiver is the single phase bipolar receiver, the controller may maintain the two other switching pairs OFF or turn the two other switching pairs OFF and control the switching of the plurality of first switching pairs and the plurality of second switching pairs such that switching pairs coupled to coils of opposite polarities of the same phase are controlled at the same time and switching pairs coupled to two phases of the three-phases are controlled simultaneously when rotationally aligned and switching pairs coupled to a third phase are controlled at a different time.

When the type of receiver is the single phase unipolar receiver, the controller may control the switching of the plurality of the first switching pairs and the plurality of second switching pairs such that the switching pairs coupled to coils of the three-phases are controlled at the same time when aligned and control the two other switching pairs to turn ON and OFF. In this aspect, the two other switching pairs may be controlled to vary a duty cycle of the three-phases.

The term "bipolar" used herein refers to a flux produced by one coil has a natural return path through its twin. For example, if the current direction through phase A+ produces a flux in the positive z-direction, then the current direction through phase A- produces a flux in the negative z-direction. In the description, where the coil assembly comprises bipolar windings (also referred to herein as coils), the windings may be referred to in pairs. The individual windings composing each pair are wound opposite in polarity. The sense of the winding direction is indicated by a + or -.

The term "polyphase" used herein refers to the transmitter and/or receiver in a wireless power transfer system having more than one phase. A polyphase system may rotate the field to transfer power.

<FIG> illustrates a block diagram of a polyphase wireless power transfer system in accordance with aspects of the disclosure. The system <NUM> comprises a transmission side (transmitter) and a reception side (receiver). The transmitter comprises a polyphase coil assembly <NUM>. In an aspect of the disclosure, the coil assembly <NUM> is unipolar, e.g., a single coil such as in <FIG> and <FIG>. In other aspects, the cols assembly <NUM> is bipolar, e.g., two coils per phase, such as in <FIG>, <FIG>, <FIG> and <FIG>.

According to the invention, there is three-phase (either unipolar or bipolar) in the transmitter. The transmitter may be used with multiple different types of receivers. The compatibility of the system is achieved via the polyphase inverter <NUM> and control thereof.

In an aspect of the disclosure, the receiver may be a polyphase receiver. In other aspects of the disclosure, the receiver may be a single phase receiver. The single phase receiver may be unipolar or bipolar. A unipolar receiver may include circular arranged coil and a bipolar receiver includes a double D or "DD" coil. The unipolar receiver is not limited to a circularly arranged coil, but may have other configurations such as square, hexagonal, etc..

The system <NUM> comprises a conversion stage <NUM>. The conversion stage <NUM> takes an input power <NUM> and converts the same to an input to a polyphase inverter <NUM>. The input power <NUM> may be a single-phase AC source. For example, the input power <NUM> may be 120VAC at <NUM>. In other aspects, the input power <NUM> may be a three-phase AC source. For example, the input power <NUM> may be obtained from a utility grid. The input power <NUM> may be 480VAC at <NUM>. The input power <NUM> may depend on the location and source. For example, the input power <NUM> may also be 400VAC at <NUM>. When the input power <NUM> is three-phase AC, the conversion stage <NUM> may be an AC to DC converter with a power factor correction. The conversion stage <NUM> may comprises a plurality of power blocks, each having one or more power modules. Each power block may convert a preset power amount. The conversion stage <NUM> may output a regulated DC voltage (DC bus) for the polyphase inverter <NUM>. The value of the DC bus may be set for a specific application. For example, in aspects of the disclosure, the DC bus is 200V. In other aspects of the disclosure, for fast charging and high power, the DC bus may be 1000V.

In other aspects of the disclosure, the input power <NUM> may be a high voltage DC source such as a high voltage battery. For example, an electric vehicle battery may be used to charge another electric vehicle battery, e.g., load <NUM>. In this example, the conversion stage <NUM> may be a DC to DC converter. The DC bus voltage may be the same as described above.

The polyphase inverter <NUM> comprises a plurality of switching pairs. The number of switching pairs may be dependent on the number of phases in the coil assembly <NUM> and polarity of the coils. For example, as shown in <FIG>, there are three sets of switching pairs for a three-phase unipolar transmitter, (set <NUM>-S1 and S2, set <NUM>, S3 and S4, set <NUM>, S5 and S6) (see also <FIG> for a three-phase bipolar transmitter). In another aspect of the disclosure, as shown in <FIG>, there are six sets of switching pairs for a three-phase bipolar transmitter, two sets for each phase, one for a positive polarity (pole) and one for a negative polarity (pole).

In an aspect of the disclosure, the polyphase inverter <NUM> further comprises an additional set of switching pairs (e.g., switches S7 and S8) (see, e.g., <FIG> and <FIG>) for configuring the transmitter for transfers to different receivers.

Each switch (hereinafter switching element) may comprise a MOSFET.

The system <NUM> further comprises a controller <NUM>. The controller <NUM> may be a microcontroller or microcontroller or any other processing hardware such as a CPU or GPU or FPGA. In an aspect of the disclosure, the controller <NUM> acts as a gate driver to turn ON and OFF each switching element of the switching pairs.

The coil assembly <NUM> comprises one or more layers of coils. The coil assembly <NUM> may be unipolar or bipolar. <FIG> illustrate an example of a three-phase bipolar coil assembly having a single layer. Each coil of the single layer assembly occupies <NUM>/<NUM> of the circumference of the layer, e.g., <NUM>°. The coil assembly <NUM> comprises a ferrite backing <NUM>. The ferrite backing <NUM> may be constructed by arranging multiple smaller ferrite tiles. The coils are positioned with a winding guide. The winding guide may be fabricated with 3D printing. The wire may be wrapped in the winding guide. The number of turns and gauge, e.g., AWG, may be based on a specific application including power density required and target size and height of the coil assembly <NUM>. The coils may be made of Litz wire. As shown in <FIG>, the coils having different polarity are positioned on opposite sides of the layer. The coils of the same phase may be connected in series. Since the coils are planar and located on a single layer, the coils A+-, B+-, C+- have the same distance to the ferrite <NUM>. The coils will also have the same self-inductance and the pairs will have the same mutual inductance.

The coils may be locked into place using a thermal epoxy (not shown). The connections with the compensation network <NUM> and polyphase inverter <NUM> are not shown in <FIG>. The connections are in-line or aligned with the coils. This allows for the coil assembly <NUM> to be thin. The coil assembly <NUM> also comprises a cover or housing (not shown in figures).

<FIG> illustrate an example of a three-phase bipolar coil assembly having a double layer (also referred to herein as dual layers or two layers). In an aspect of the disclosure, coils having one polarity, e.g., A+, B+ and C+ are arranged on one layer, whereas coils having another polarity, e.g., A-, B-, and C- are arranged on the other layer. As shown in <FIG>, the coils are staggered in the stacked direction. For example, the coils may be staggered by <NUM>°. Each coil occupies <NUM>/<NUM> of the circumference of the layer, e.g., <NUM>°. As shown in <FIG>, the coils having different polarity are positioned on opposite sides of the layer. For example, coil A- may be located on a top layer, where coil A+ is located on a bottom layer on the opposite side, e.g., <NUM>° offset. The coils of the same phase may be connected in series. As shown in <FIG>, the coils on the top layer are farther from the ferrite <NUM> than coils on the bottom layer. The windings on one layer will have one set of self- and mutual-inductances, and the windings on the other layer will have a different set of self- and mutual-inductances. However, since the positive and negative poles of each phase occur on different layers, when the individual phase coils in the double layer are connected in series, the overall system may have balanced inductances.

The connections with the compensation network <NUM> and polyphase <NUM> are not shown in <FIG>. The connections are in-line or aligned with the coils (see <FIG> and <FIG>). This allows for the coil assembly <NUM> to be thin.

The coils are also positioned with a winding guide. The winding guide may be fabricated with 3D printing, where the winding guide may be on both the top and the bottom on a printed structure. The wire may be wrapped in the winding guide. As with the single layer assembly, the coils are fixed in positioned with a thermal epoxy. The coil assembly <NUM> having a double layer also comprises a cover or housing (not shown in figures).

<FIG> illustrate an example of a three-phase bipolar coil assembly having a triple layer (also referred to herein as three layers). In this aspect, each layer has a different phase. For example, one layer as coils B+-, another layer as A+- and another layer has C+-. The coils for the same phase are located on opposite sides of the layer, e.g., <NUM>°. The coils also occupy <NUM>/<NUM> of the circumference of the layer, e.g., <NUM>°. The distance between the coils for each phase and the ferrite <NUM> are different. Therefore, each phase has an unbalanced inductance.

In some aspects, there may be spacers between layers of coils.

While <FIG> show the coil assemblies <NUM> with three-phases according to the claimed invention this disclosure is not limited to three, and this will be hereby discussed for illustrative purposes. In other aspects of the disclosure, the coil assembly <NUM> may comprises two-phases to create a rotating magnetic field. In this aspect, the coil assembly may be a single layer, such as in <FIG> or two layers, such as shown in <FIG>. In the single layer, each coil may occupy ¼ of the circumference, e.g., <NUM>°. In the two layer coil assembly <NUM>, each coil may occupy ½ of the circumference, e.g., <NUM>°. In an aspect of the disclosure, coils of one polarity may be located on one layer and coils of the other polarity may be located on the other layer. In other aspects, coils for one phase may be located on one layer and coils for the second phase may be located on the second. In this aspect, the inductances may be unbalance. The two phase coil assembly <NUM> may have more DC-link current ripple compared with a three-phase coil assembly.

In other aspects, not covered by the claimed scope, but included in this description for illustrative purposes, more than three-phases may be used. For example, five-phase, seven-phase, and higher phase systems may be used in the coil assembly <NUM>. However, the number of phases is not limited to odd numbers. In this aspect, these coil assembly arrangements may have the benefit of reduced DC-link current ripple. For planar couplers, power transfer is proportional to <NUM>) the number of layers, and <NUM>) the coil span of each phase. Typically, there is a tradeoff between the number of phases and the coil span for each phase in a planar coil assembly, such as the coil assemblies <NUM> described herein. The coil span decreases with an increase in phases. However, larger coil spans are generally preferred to maximize the coupling between the transmitter and the receiver. Alternatively, additional layers may be added, but this will increase either the package thickness or winding voltage. Increasing the number of layers also may increase inductance imbalances between the phases. Further, increasing the phases may impact harmonics. For example, in a three-phase coil assembly <NUM>, the third harmonic may be canceled, which may mitigate some EMI and reduce losses associated with a prominent third harmonic. However, in higher phases, the fifth, seventh, etc. harmonic may be canceled rather than the third harmonic.

Also, because each layer has a different distance from the ferrite <NUM>, the coils on different layers may have different self-inductances and the mutual inductance between the phase coils may depend on the layer of each pair of coils.

The system <NUM> further comprises a compensation network <NUM>. In accordance with aspects of the disclosure, the compensation network <NUM> is tuned to achieve at least two independently excitable resonant modes for a single resonant frequency. For example, the two resonant modes may be α-mode (α-axis mode) and a β-mode (β-axis mode). <FIG> shows the relationship between the α-axis, the β-axis and the γ-axis and the coil placement. The α-axis is aligned with phase A. The β-axis is aligned with a midpoint between phases B and C. The γ-axis is orthogonal to both the α-axis and the β-axis and would point out of the coil plane. Arrows in <FIG> represent the axis orientation.

Once tuned, the α-mode and β-mode can be excited independently to produce a resonant rotating magnetic field. For example, they may be excited in quadrature (<NUM>-degrees phase shifted in time) to achieve high-efficiency constant power transfer. <FIG> show examples of an α-mode and β-mode, respectively. In <FIG>, the coils are not explicitly shown, however, the location is represented by letters A+, A-, B+, B-, C+ and C-, which are bipolar coils for the three-phases, A, B and C. The circular arrows represent the in-plane electrical current for each phase. As can be seen in the figure, the direction of the arrow for the different polarity is opposite. For example, for coil A+, the direction is counter-clockwise, however for coil A-, the direction is clockwise. The magnitude and direction of the magnetic flux density (which is out of the plane), e.g., out of the page, is represented by different shading. The magnitude is normalized relative to a maximum flux density for the α excitation mode, e.g., -<NUM> to <NUM>. As can be seen in <FIG>, the maximum flux density (close to <NUM> or -<NUM>) is aligned with the area where coils A+ or A- are located in the α-mode. However, as can be seen in <FIG>, in the β-mode, the flux density is rotated such that the maxiumun flux density (close to <NUM> or -<NUM>) is located in an area where coils B+, B-, C+ and C- are located.

<FIG> show examples of an α-mode and β-mode, respectively, for a single layer coil assembly, such as shown in <FIG>. The arrows represent the magnetic and direction of the current density. The magnitude and direction of the magnetic flux density (z-component) is represented by different shading. Once again, the magnitude is normalized relative to a maximum flux density for the α excitation mode, e.g., -<NUM> to <NUM>.

In the α-mode (<FIG>), the current density and the magnetic density is highest where phase A, e.g., coils A+ and A- are located.

In the β-mode (<FIG>), the current density and the magnetic density is highest for phases B and C. The flux density is rotated such that the maxiumun flux density (close to <NUM> or -<NUM>) is located in an area where coils B+, B-, C+ and C- are located.

<FIG> show examples of an α-mode and β-mode, respectively, for a double layer coil assembly, such as shown in <FIG>. The arrows represent the magnetic and direction of the current density. The magnitude and direction of the magnetic flux density (z-component) is represented by different shading. Once again, the magnitude is normalized relative to a maximum flux density for the α excitation mode, e.g., -<NUM> to <NUM>.

Since the coils occupy a larger area in the double layer coil assembly, the areas showing higher electric current and magnetic flux are larger compared with the single layer coil assembly. <FIG> shows the electric current flowing in both layers.

In the α-mode (<FIG>), the current density and the magnetic flux density is highest where phase A, e.g., coils A+ and A- are located.

In the β-mode (<FIG>), the current density and the magnetic flux density is highest for phases B and C. The flux density is rotated such that the maxiumun flux density (close to <NUM> or -<NUM>) is located in an area where coils B+, B-, C+ and C- are located and in particular, as shown in <FIG>, the maxmium flux density is located where phases B and C overlap.

<FIG> shows examples of an α-mode and β-mode, respectively, for a triple layer coil assembly, such as shown in <FIG>. The arrows represent the magnetic and direction of the current density. The arrows represent current on the three layers. The magnitude and direction of the magnetic flux density (z-component) is represented by different shading. Once again, the magnitude is normalized relative to a maximum flux density for the α excitation mode, e.g., -<NUM> to <NUM>.

Since the coils occupy a larger area in the triple layer coil assembly, than both the double layer coil assembly and the single layer coil assembly, the areas showing higher electric current and magnetic flux are larger compared with the single layer coil assembly and the double layer coil assembly.

In the α-mode (<FIG>), the current density and the magnetic flux density is highest where phase A, e.g., coils A+ and A- are located. As shown in <FIG>, the maximum flux density (close to <NUM> and -<NUM>), occupies a large portion of the assembly.

According to the invention, the compensation network <NUM> includes a capacitance. The capacitance may be in the form of a single capacitor for each phase or multiple capacitors, for example, capacitance Ca, Cb, Cc, connected in series with the coil for each phase, e.g., La, Lb and Lc, respectively. The compensation network, such as the series capacitance, and the coils may be connected in various different topologies (herein referred to as series resonant network topologies). <FIG> illustrate four different series resonant network topologies for three-phases. In the figures, the coils for the phases are represented by La, Lb and Lc and the capacitance for the phases are represented by Ca, Cb, Cc. For example, the tuning capacitance for phase A is Ca and so on. <FIG> is a ΔC-ΔL configuration; <FIG> is a YC- ΔL configuration; <FIG> is a ΔC-YL configuration; and <FIG> is a YC-YL configuration. Δ refers to a delta configuration and Y refers to a wye configuration.

In accordance with aspects of the disclosure, the values of the capacitance, Ca, Cb, Cc may have different values based on the different series resonant network topologies and coil assembly design. For example, a coil assembly having three layers may have an unbalanced self and mutual inductance, whereas a coil assembly having one or two layers may have a balanced self and mutual inductance.

For purposes of the description the mutual inductance between phase A and phase B is represented as Mab, the mutual inductance between phase B and phase C is represented as Mbc and the mutual inductance between phase C and phase A is represented as Mca· When the coil assembly <NUM> has a balanced mutual inductance: <MAT>.

Thus, the mutual inductance may be referred to as M, when balanced.

The self inductance is also balanced where <MAT>.

Thus, the inductance may be referred to as L, when balanced. The effective inductance associated with a balance system is L', where <MAT>.

The capacitance for a ΔC-ΔL resonant network topology such as shown in <FIG> may be determined based on the following:
when balanced: <MAT>
where L' is defined in equation <NUM>, ω is the resonant frequency, and i is the phase, such as a, b, or c for the three-phase system.

When the coil assembly <NUM> has an unbalance self and mutual inductance, such as when the coil assembly is three layers, the capacitance for a ΔC-ΔL resonant network topology such as shown in <FIG> may be determined based on the following: <MAT>
where L' is defined in equation <NUM>, ω is the resonant frequency, and i, j, and k are the phases, such as a, b, or c for the three-phase system. For example, when i is a, j is b and k is c. When i is b, j is c and k is a and when i is c, j is a and k is b. For instance, when i is a, Mjk is Mbc, Mij is Mab and Mki is Mca·.

The capacitance for a YC-ΔL resonant network topology such as shown in <FIG> may be determined based on the following:
when balanced: <MAT>
where L' is defined in equation <NUM>, ω is the resonant frequency, and i is the phase, such as a, b, or c for the three-phase system.

When the coil assembly has an unbalance self and mutual inductance, such as when the coil assembly is three layers, the capacitance for a YC-ΔL resonant network topology such as shown in <FIG> may be determined based on the following: <MAT>
where L' is defined in equation <NUM>, ω is the resonant frequency, and i, j, and k are the phases, such as a, b, or c for the three-phase system. For example, when i is a, j is b and k is c. When i is b, j is c and k is a and when i is c, j is a and k is b, Lσ which is a sum of intermediate inductances, is defined as follows: <MAT>
and the intermediate inductances for a Δ-connected inductor system(ΔL) are <MAT>.

In equation <NUM>, i, j and k are the phases and may be a, b or c. For instance, when i is a, Li is La, Mij is Mab and Mki is Mca· Similarly, when i is b, Li is Lb, Mij is Mbc and Mki is Mab and when i is c, Li is Lc, Mij is Mca and Mki is Mbe. The same is true in equations <NUM> and <NUM>.

The capacitance for a ΔC-YL resonant network topology such as shown in <FIG> may be determined based on the following:
when balanced: <MAT>
where L' is defined in equation <NUM>, ω is the resonant frequency, and i is the phase, such as a, b, or c for the three-phase system.

When the coil assembly has an unbalance self and mutual inductance, such as when the coil assembly is three layers, the capacitance for a ΔC-YL resonant network topology such as shown in <FIG> may be determined based on the following: <MAT>.

ω is the resonant frequency, and i, j, and k are the phases, such as a, b, or c for the three-phase system. For example, when i is a, j is b and k is c. When i is b, j is c and k is a and when i is c, j is a and k is b, and the intermediate inductances associated with the Y-connected inductors (YL) are determined as follows: <MAT>.

Like in the other equations, i, j and k, are the phases and may be a, b or c. For instance, when i is a, Li is La, Mij is Mab , Mjk is Mbc and Mki is Mca· Similarly, when i is b, Li is Lb, Mij is Mbc, Mjk is Mca and Mki is Mab and when i is c, Li is Lc, Mij is Mca, Mjk is Mab and Mki is Mbe.

The capacitance for a YC-YL resonant network topology such as shown in <FIG> may be determined based on the following:
when balanced: <MAT>
where L' is defined in equation <NUM>, ω is the resonant frequency, and i is the phase, such as a, b, or c for the three-phase system.

When the coil assembly has an unbalance self and mutual inductance, such as when the coil assembly is three layers, the capacitance for a YC-YL resonant network topology such as shown in <FIG> may be determined based on the following: <MAT>
where ω is the resonant frequency, and i is the phase, such as a, b, or c for the three-phase system and the intermediate inductances <MAT> are determined by equation <NUM>.

The types of resonant networks for the system <NUM> are not limited to the topologies illustrated in <FIG> and other resonant networks may be used. For example, the resonant network may comprise an LCC configuration as shown in <FIG>. The values of the tuning capacitance (compensation capacitance) in each of these configurations may also be different from each other based on the type.

As described above, the transmitter described herein is compatible to transfer power to different types of receivers.

<FIG> depicts a schematic diagram of a polyphase wireless power transfer system in accordance with aspects of the disclosure. The input power <NUM>, conversion stage <NUM> and controller <NUM> are not shown in <FIG>. Additionally, the receiver controller <NUM> and the load are also not shown. The receiver controller <NUM> controls the inverter <NUM>, e.g., gate driver. The coil assembly <NUM> in <FIG> is unipolar. The coil assembly is represented in <FIG> as three inductors. The inductors L are connected in a wye configuration (YL). While the inductors are labeled L in the figure, the inductance of each may be different. The compensation network <NUM> comprises series capacitance (Cp). Although the capacitance in each phase is referred to in <FIG> as Cp, the values of the capacitance may be different depending on the number of layers in the assembly <NUM> and the values may be different based on equations <NUM> or <NUM> depending on the balance of the self and mutual inductance. <FIG> depicts one compensation network and inductor configuration, however, other configurations such as depicted in <FIG> and <FIG> may be used.

The polyphase inverter <NUM> comprises a plurality of switching elements S1-S6. These switching elements are switching pairs. One switching pair for a respective phase. For example, switching elements S1 and S2 are for phase a, switching elements S3 and S4 are for phase b and switching elements S5 and <NUM> are for phase c. The polyphase inverter <NUM> also comprises switching elements S7 and S8 (additional switching pair). These switching elements S7 and S8 are to configure the transmitter for different receivers. Switching elements S1-S6 may also be controlled to allow for power transfer to different receivers.

The transmitter may have an inductor Ln connected to the neutrals N and to a node n between the switching elements S7 and S8.

The switching elements in each pair (S <NUM>-S6) may be complementary. For example, when switching element S <NUM> is turned ON, switching element S2 (same pair) is turned OFF. The space vector hexagon in <FIG> describes the <NUM> combinations of switch states. For example, state V1 with switch states (<NUM>) means that the S1 is ON and S2 is off, S3 is OFF and S4 is ON, and S5 is OFF and S6 is ON.

Control of a three-phase inverter (such as inverter <NUM>) may be accomplished by visiting states V1, V2, V3, V4, V5, and V6 in the space-vector voltage hexagon in <FIG> in either a counterclockwise or clockwise manner over one time period associated with the operating frequency. The zero states V0 and V7 represented at the center of the hexagon may visited between states V1 through V6. A general switching scheme may be V1-(V0 or V7)-V2-(V0 or V7)-V3-(V0 or V7)-V4-(V0 or V7)-V5-(V0 or V7)-V6. The times spent in any group of states could be equal or different. The times spent in any of the states could be zero, so that the state is skipped. The times spent in any of the states can be adjusted to control the power transferred to the receiver. The times spent in any of the states can be adjusted based on the type of receiver as described below. The times spent in any of the states can also be adjusted based on the degree of rotational misalignment between the transmitter and receiver as described below. The times spent in any of the states can also be adjusted based on the degree and direction of translational misalignment between the transmitter and receiver as described below. In an aspect of the disclosure, only the type of receiver, only the rotational misalignment or only translational misalignment may be used to adjust the times spent in any of the states. In other aspects, any combination of two or more of the type of receiver, rotational misalignment and translational misalignment may be used. For example, all three of the type of receiver, rotational misalignment and translational misalignment may be used. For example, the type of receiver and rotational misalignment or the type of receiver and translational misalignment may be used. In another example, the rotational and translational misalignment may be used.

As depicted in <FIG>, the receiver is a three-phase receiver. The coil assembly <NUM> of the receiver is represented in <FIG> with three inductors Lr. An advantage of the disclosed transmitter is that the coil assembly <NUM> in the transmitter and the coil assembly <NUM> in the receiver does not need to be the same. The inductance may or may not be the same as the inductance of the transmitter coils. While the inductors Lr are depicted in a wye configuration YL, the inductors in the receiver may have Δ configuration. The compensation network <NUM> is depicted in <FIG> as series capacitance Cs. The value of the capacitance is determined in the same manner as described above. <FIG> also depicts an inverter <NUM> in the receiver. As depicted, the inverter <NUM> has three pairs of switching elements, Sr which correspond to the three-phases. This allows for bi-directional power transfer. However, in other aspects of the disclosure, the inverter <NUM> may be replaced with a rectifier where bi-directional power transfer is not needed.

In an aspect of the disclosure, the system <NUM> may use wireless communication to transmit information regarding the receiver configuration. For example, the receiver side and the transmission side may include a wireless interface. The wireless interface may be WIFI. In other aspects of the disclosure, the interface may be a near field communication interface such as a BLE interface. In other aspects, the receiver may comprise an RFID tag and the transmitter may include an RFID reader. The reader may interrogate the RFID tag. The RFID tag may contain the receiver configuration. The RFID tag may, in response to the interrogation, transmit the receiver configuration.

In other aspects of the disclosure, the type of receiver may be determined by applying test switching waveforms. In this aspect of the disclosure, the controller <NUM> will cycle through a plurality of excitation modes and detect electrical properties. The electrical properties may comprise transmitting coils currents, e.g., inductor currents and inverter currents. The currents may be detected via current sensors (not shown). The current sensors may be hall-effect current sensors. In other aspects, the current sensors may use sense resistors and shunt sensing circuits. The controller <NUM> also comprises a memory. This memory may store a look up table for the electrical properties associated with a type. Different types of receivers may cause different electrical properties in the transmitter (coil and inverter). The different electrical properties may be used to discriminate the type of receiver. Each mode, such as, but not limited to, α-mode, β-mode and γ-mode may be excited for a preset period of time in order to measure the electrical properties. The measured electrical proprieties may be stored. The controller <NUM> may use any order of excitation.

In some aspects of the disclosure, the memory may also have the different electrical properties associated with the types for different translational and rotational alignments.

The following describes an example of the determination of the receiver type in accordance with aspects of the disclosure. The controller <NUM> may enter a test switching mode in response to a command such as a notification from a camera. In other aspects, a wireless interface in the receiver may transmit a notification to the transmitter (wireless interface). This notification may include the amount of power needed for charging and indicate presence at the charger. In response, the controller <NUM> causes a first excitation mode to be excited. For example, the controller <NUM> controls the switching elements in the inverter <NUM> to cause the first excitation mode to be excited. For purposes of the description, this mode may be the α-mode. The controller <NUM> subsequently receives the detected currents, e.g., inverter and coils. The controller <NUM> may wait a set period of time to record the current to allow for the system to reach a steady-state. The controller repeats this process for the second excitation mode and a third excitation mode. For purposes of the description, these modes may be the β-mode and γ-mode. Additional modes may be excited depending on the coil assembly configuration. Additionally, both the α-mode and β-mode may be excited at the same time.

Once the test excitation modes are completed. The controller <NUM> may compare the measured and recorded currents with the prestored currents (for both the inverter and coils) in the look up table. The type of receiver that has the prestored currents match the measured currents for the test modes, is determined as the type of receiver. Matching for the determination includes the type having the prestored values be the closest to the measured values.

After the controller <NUM> determines the type of receiver as described above, the controller <NUM> may control the inverter <NUM> based on the determined type such as described below.

The transmitter in <FIG> may be used to transfer power to different receivers such as a three-phase, a single phase DD or a single phase circular (as described above, the single phase receiver may have a different configuration such as square, hexagonal, etc.).

<FIG> illustrates an example of a transmitter inverter control for power transfer to a receiver having three-phases, e.g., three-phase operation. In <FIG>, the switching period is π. The voltage Vao represents the voltage at node a; Vbo represents the voltage at node b; and Vvo represents the voltage at node c.

The voltage cycles from + to - and vice versa. For example, the positive voltage reflects when switching element S <NUM> is ON (S2 OFF) and the negative voltage reflects when switching element S2 is ON (S <NUM> OFF). For example, between <NUM> and π, S <NUM> is ON and S2 is OFF and at π S <NUM> is switched OFF and S2 is switched on. For the three-phase operation, the switching time is offset for the respective switching pairs. This is reflected in the shift in the voltage square waves at Vao, Vbo and Vco. In an aspect of the disclosure, in the three-phase operation, the shift is (<NUM>/<NUM>) π. Switching elements S1 and S2 are operated at different times from switching elements S3 and S4, which are also operated at different times from switching elements S5 and S6.

Also for the three-phase operation, switching elements S7 and S8 are maintained OFF, as reflected in the flat line for the voltage Vno, which is the voltage at node n. <FIG> depicts the switching timing for a quadrature phase shift in the α-mode and the β-mode, however, other phases shifts may be used. A quadrature phase shift may be used when the transmitting coils and the receiving coils are aligned with respect to each other. In accordance with aspects of the disclosure, the control of the switching elements may be based on a translational (not aligned) state between the transmitting coils and the receiving coils. For example, the controller may change the time spent in each switching state (states are shown in <FIG>) based on the translation. For example, if the transmitting coils and the receiving coils are translated in the x-axis, the controller <NUM> may control the switching to spend more time in state V1 and V4, whereas if the transmitting coils and the receiving coils are translated in the y-axis, the controller <NUM> may control the switching to spend more time in states V2, V3, V5 and V6.

In an aspect of the disclosure, misalignment (translational and rotational) may be transmitted from the receiver to the transmitter via the wireless interface. In other aspects of the disclosure, the system <NUM> may also have a camera. The camera may be optical or infrared. In this aspect of the disclosure, the camera may detect a misalignment (both translational and rotational) and notify the controller <NUM> of such a condition. The controller <NUM> may control the switching elements based on the notification. The notification may include the amount of misalignment (translational and rotational) and the time spent at the states or which states may be based on the amount of the misalignment.

In other aspects of the disclosure, the alignment (translational and rotational) may be determined using the look up table in a similar manner as described above. For example, the controller <NUM> may compare the measured currents for the plurality of excitation modes with the prestored currents under different known alignment conditions (translational and rotational) (for the different types). The alignment condition that has the prestored currents match the measured currents for the test modes, is determined as actual alignment condition (translational and rotational). Matching for the determination includes the alignment condition having the prestored values be the closest to the measured values. After the controller <NUM> determines the alignment condition, the controller <NUM> may control the inverter <NUM> based on the determination.

The switching may be controlled via a gate driver (not shown in <FIG>).

<FIG> depicts the same transmitter, e.g., three-phase unipolar. However, in <FIG>, the receiver has a single phase, e.g., coils Ls. As shown in <FIG>, the coils Ls may have a bipolar configuration, e.g., DD. <FIG> illustrates an example of the alignment of the three-phases A, B and C of the transmitter with the single phase DD receiver. In the receiver, the inverter <NUM> may be configured as a H-bridge, one pair of switching elements coupled to one end of the inductor and the other pair of switching elements coupled to the other end.

<FIG> illustrates an example of a transmitter inverter control for power transfer to a receiver having a single phase with a DD configuration, e.g., single phase DD operation. In <FIG>, the switching period is π. The voltage Vao represents the voltage at node a; Vbo represents the voltage at node b; and Vvo represents the voltage at node c.

Unlike the operation shown in <FIG>, for the single phase DD operation, two of the phases are switched at the same time when the transmitting coils and the receiving coils are aligned and not rotated. In <FIG>, phases b and c are switched at the same time. Thus, the inverter <NUM> operates as a single phase inverter where one leg of the output may be phase A while the other leg is composed of phases b and c. As depicted, the α-mode is excited. Additionally, the switching timing depicted is when the transmitting coils and the receiving coils are aligned and not rotated with respect to each other. For example, when aligned and not rotated, the switching states may be V7-V1-V0-V4. Also for the single phase DD operation, switching elements S7 and S8 are maintained OFF as reflected in the flat line for the voltage Vno, which is the voltage at node n. When the transmitting coils and the receiving coils are rotated with respect to each other, the controller <NUM> may change the switching timing (states). In an aspect of the disclosure, the switching states may depend on the amount of the rotation. For example, for <NUM>° rotation, both the α-mode and the β mode may be excited. The switching states may be V5-V7-V2-V0. In another example, for a <NUM>° rotation, the β mode may be excited. States V1 and V4 may be omitted. Additionally, when the transmitting coils and the receiving coils are translated with respect to each other, the controller <NUM> may change the switching timing (states). In an aspect of the disclosure, the switching states may depend on the direction and magnitude of the translation. For example, for a translation along the x-axis, both the α-mode and the β mode may be excited. The switching states may be V1-V2-V3-V4-V5-V6. In another example, for translation along a vector oriented <NUM>° from the x-axis, the switching states may be V1-V2-V4-V5, with states V3 and V6 omitted.

The receiver in <FIG> may also have a circular coil configuration, e.g., unipolar. <FIG> depicts the transmitter and receiver coil alignment for the circular receiver coil configuration. The circular coil aligns with the three-phases A, B and C.

<FIG> illustrates an example of a transmitter inverter control for power transfer to a receiver having a single phase with a circular configuration, e.g., single phase circular operation. In <FIG>, the switching period is π. The voltage Vao represents the voltage at node a; Vbo represents the voltage at node b; Vvo represents the voltage at node c; and Vno represents the voltage at node m.

Unlike the three-phase operation and the single phase DD operation, for the single phase circular operation, switching elements S7 and S8 are switched. Additionally, the switching element pairs S <NUM>-S6 for each phase are switched at the same time. S <NUM>, S3 and S5 are switched at the same time and S2, S4 and S6 are switched at the same time. As depicted in <FIG>, the positive voltage at node n occurs when switching element S7 is turned ON (and S8 is turned OFF) and the negative voltage at n occurs when the switching element S8 is turned ON (and S7 is turned OFF).

As depicted in <FIG>, a γ-mode is excited. This may occur when the transmitting coils and the receiving coils are aligned (not translated). The switching states include V0 and V7. As depicted in <FIG>, the timing when the switching elements S7 and S8 are controlled is offset from the timing when the switching elements S <NUM>-S6 are controlled, e.g., switched. The relative timing of the switching may be adjusted to control the duty cycle. The closer of the relative switching timing reduces the duty cycle. In some aspects, when the transmitting coils and the receiving coils are not aligned, the switching states may be changed, e.g., the controller changes the switching such that other modes may be excited. For example, for translational misalignment along a vector oriented at <NUM>° from the x-axis, the switches may use states V1-V2-V5-V6.

<FIG> depicts a schematic diagram of another polyphase wireless power transfer system in accordance with aspects of the disclosure. The input power <NUM>, conversion stage <NUM> and controllers <NUM> and <NUM> and load <NUM> are not shown in <FIG>. The coil assembly <NUM> in <FIG> is bipolar (referred as Lbp in <FIG>). In <FIG>, the inductors are labeled Lbp, however, each inductor may have a different inductance. The inverter <NUM> in <FIG> is similar to the inverter <NUM> in <FIG> except that switching elements S7 and S8 are removed.

Inductor Ln is also not included in the transmitter in <FIG>.

The inductors are connected in a wye configuration (YL). The compensation network <NUM> comprises series capacitance (Cp). While <FIG> depicts a YC-YL configuration, any of the resonant networks described herein may be used (see <FIG>, <FIG>). Although each is referred in <FIG> as Cp, the values of the capacitance may be different depending on the number of layers in the assembly and the values may be different based on equations <NUM> or <NUM> depending on the balance of the self inductance and mutual inductance. The coil assembly <NUM> may have the configurations as depicted in <FIG>.

The switching elements S <NUM>-S6 may be the same as discussed above in <FIG> and may be controlled by a gate driver.

The transmitter may transfer power to a three-phase receiver or a single phase DD configured receiver. The receiver in <FIG> is a three-phase receiver and the receiver in <FIG> is a single phase DD configured receiver.

<FIG> illustrates an example of a transmitter inverter control for power transfer to a receiver having three-phases, e.g., three-phase operation, for the transmitter in <FIG>. In <FIG>, the switching period is π. The voltage Vao represents the voltage at node a; Vbo represents the voltage at node b; and Vvo represents the voltage at node c.

The timing of switching the switching elements S1-S6 is the same in <FIG> as in <FIG>. For example, for the three-phase operation, the switching time is offset for the respective switching pairs. This is reflected in the shift in the voltage square waves at Vao, Vbo and Vco. <FIG> depicts the switching timing for a quadrature phase shift in the α-mode and the β-mode, however, other phases shifts may be used. A quadrature phase shift may be used when the transmitting coils and the receiving coils are aligned with respect to each other. In accordance with aspects of the disclosure, the control of the switching elements may be based on a translational (not aligned) state between the transmitting coils and the receiving coils. For example, the controller <NUM> may change the time spent in each switching state (states are shown in <FIG>) based on the translation. For example, if the transmitting coils and the receiving coils are translated in the x-axis, the controller may control the switching to spend more time in state V1 and V4, whereas if the transmitting coils and the receiving coils are translated in the y-axis, the controller <NUM> may control the switching to spend more time in states V2, V3, V5 and V6.

<FIG> illustrates an example of a transmitter inverter control for power transfer to a receiver having a single phase DD configuration, e.g., single phase DD operation, for the transmitter in <FIG>. While <FIG> depicts a YC-YL configuration, any of the resonant networks described herein may be used (see <FIG>, <FIG>). In <FIG>, the switching period is π. The voltage Vao represents the voltage at node a; Vbo represents the voltage at node b; and Vvo represents the voltage at node c.

The timing of switching the switching elements S1-S6 is the same in <FIG> as in <FIG>. For example, for the single phase DD operation, two of the phases are switched at the same time when the transmitting coil and the receiving coils are aligned and not rotated. In <FIG>, phases b and c are switched at the same time. Thus, the inverter operates as a single phase inverter where one leg of the output may be phase A while the other leg is composed of phases b and c. As depicted, the α-mode is excited. Additionally, the switching timing depicted is when the transmitting coils and the receiving coils are aligned and not rotated with respect to each other. For example, when aligned and not rotated, the switching states may be V7-V1-V0-V4.

When the transmitting coils and the receiving coils are rotated with respect to each other, the controller <NUM> may change the switching timing (states). In an aspect of the disclosure, the switching states may depend on the amount of the rotation. For example, for <NUM>° rotation, both the α-mode and the β mode may be excited. The switching states may be V5-V7-V2-V0. In another example, for a <NUM>° rotation, the β mode may be excited. States V1 and V4 may be omitted. Additionally, when the transmitting coils and the receiving coils are translated with respect to each other, the controller <NUM> may change the switching timing (states). In an aspect of the disclosure, the switching states may depend on the direction and magnitude of the translation. For example, for a translation along the x-axis, both he α-mode and the β mode may be excited. The switching states may be V1-V2-V3-V4-V5-V6. In another example, for translation along a vector oriented <NUM>° from the x-axis, the switching states may be V1-V2-V4-V5, with states V3 and V6 omitted.

<FIG> depicts a schematic diagram of another polyphase wireless power transfer system in accordance with aspects of the disclosure. As with the other figures, e.g. <FIG>, <FIG>, <FIG>, and <FIG>, the input power <NUM>, conversion stage <NUM> and controllers <NUM> and <NUM> and load <NUM> are not shown in <FIG>.

The transmitter in <FIG> is compatible with receivers having three-phases, a single phase with DD configuration and a single phase circular configuration. In <FIG>, the transmitter is bipolar similar to the transmitter in <FIG> and <FIG> (three-phase). However, a difference in the transmitter in <FIG> and <FIG> and <FIG>, is that coils having different polarities are connected to different switching elements. In <FIG>, coils of a first polarity, e.g., positive, are represented as A+, B+ and C+ and coils of the opposite polarity, e.g., negative, are represented as A-, B- and C-. Coils of each polarity are connected to the inverter <NUM> in a similar manner as described in <FIG>. The coils of the different phases may or may not have the same inductance. Coils of the same phase may or may not have the same inductance. <FIG> depicts one compensation network and inductor configuration, however, other configurations such as depicted in <FIG> and <FIG> may be used.

For example, a first pair of switching elements S1 and S2 are connected to the positive phase A+ and a second pair of switching elements S1 and S2 are connected to the negative phase A-. A first pair of switching elements S3 and S4 are connected to the positive phase B+ and a second pair of switching elements S3 and S4 are connected to the negative phase B-. Similarly, a first pair of switching elements S5 and S6 are connected to the positive phase C+ and a second pair of switching elements S5 and S6 are connected to the negative phase C-. The connections to the positive phase component, A+, B+ and C+ and the negative phase component, A-, B- and Care similar to <FIG> for the unipolar aspects of the disclosure.

Node A+ (A+<NUM>) is between a first pair of switching elements S1 and S2 and node A- (a-o) is between the second pair of switching elements S1 and S2. Node B+ (B+<NUM>) is between a first pair of switching elements S3 and S4 and node B- (B-o) is between the second pair of switching elements S3 and S4. Node C+ (C+<NUM>) is between a first pair of switching elements S5 and S6 and node C- (C-o) is between the second pair of switching elements S5 and S6.

Also like in <FIG>, there may be an inductance Ln between the neutral N and the respective node n+ or n-.

The polyphase inverter <NUM> also comprises first and second pairs of switching elements S7 and S8 (additional switching pairs). These switching elements S7 and S8 are to configure the transmitter for the different receivers. One pair of switching element S7 and S8 are coupled to node n+ and the other is coupled to n-. Switching elements pairs S <NUM>-S6 may also be controlled to allow for power transfer to the different receivers.

As depicted in <FIG>, the receiver has three-phases similar to the receiver in <FIG>.

<FIG> illustrates an example of a transmitter inverter control for power transfer to a receiver having a three-phase configuration, e.g., three-phase operation, for the transmitter in <FIG>. In <FIG>, the switching period is π. As shown in <FIG>, the node A+ and node A- have opposite relationships, e.g., A+ being positive when A- is negative and vice versa. Similarly, the node B+ and node B- have opposite relationships, e.g., B+ being positive when B- is negative and vice versa and the node C+ and node C- have opposite relationships, e.g., C+ being positive when C- is negative and vice versa.

As in <FIG>, the timing for the different phases to be switched is different, e.g. staggered, such that different square waves for the different phases are offset. Switching elements pairs S <NUM> and S2 are operated at different times from switching elements pairs S3 and S4, which are also operated at different times from switching elements pairs S5 and S6.

<FIG> depicts the switching timing for a quadrature phase shift in the α-mode and the β-mode, however, other phases shifts may be used. A quadrature phase shift may be used when the transmitting coils and the receiving coils are aligned with respect to each other. In accordance with aspects of the disclosure, the control of the switching elements may be based on a translational (not aligned) state between the transmitting coils and the receiving coils. For example, the controller <NUM> may change the time spent in each switching state (states are shown in <FIG>) based on the translation. For example, if the transmitting coils and the receiving coils are translated in the x-axis, the controller <NUM> may control the switching to spend more time in state V1 and V4, whereas if the transmitting coils and the receiving coils are translated in the y-axis, the controller <NUM> may control the switching to spend more time in states V2, V3, V5 and V6.

Switching elements for the same phase may be operated at the same time. For example, switching element S <NUM> coupled to A+ is operated at the same time as switching element S <NUM> coupled to A-. However, the relationship may be complementary.

Also for the three-phase operation, switching elements pair S7 and S8 are maintained OFF as reflected in the flat line for the voltage Vn+<NUM> and Vn-<NUM>·.

<FIG> depicts the same transmitter, e.g., three-phase bipolar. However, in <FIG>, the receiver has a single phase, e.g., coils Ls. <FIG> illustrates an example of a transmitter inverter control for power transfer to a receiver having a single phase with a DD configuration, e.g., single phase DD operation. In <FIG>, the switching period is π.

For the single phase DD operation, two of the phases are switched at the same time. In <FIG>, phases B+ and B- and C+ and C- are switched at the same time when the transmitting coil and the receiving coils are aligned and not rotated. Thus, the inverter <NUM> operates as a single phase inverter where one leg of the output may be phase A+/A- while the other leg is composed of phases B+- and C+-. Also for the single phase DD operation, switching elements pairs S7 and S8 are maintained OFF as reflected in the flat line for the voltage Vn+<NUM> and Vn-<NUM>· As depicted, the α-mode is excited. Additionally, the switching timing depicted is when the transmitting coils and the receiving coils are aligned and not rotated with respect to each other. For example, when aligned and not rotated, the switching states may be V7-V1-V0-V4.

When the transmitting coils and the receiving coils are rotated with respect to each other, the controller may change the switching timing (states). In an aspect of the disclosure, the switching states may depend on the amount of the rotation. For example, for <NUM>° rotation, both the α-mode and the β mode may be excited. The switching states may be V5-V7-V2-V0. In another example, for a <NUM>° rotation, the β mode may be excited. States V1 and V4 may be omitted. Additionally, when the transmitting coils and the receiving coils are translated with respect to each other, the controller <NUM> may change the switching timing (states). In an aspect of the disclosure, the switching states may depend on the direction and magnitude of the translation. For example, for a translation along the x-axis, both he α-mode and the β mode may be excited. The switching states may be V1-V2-V3-V4-V5-V6. In another example, for translation along a vector oriented <NUM>° from the x-axis, the switching states may be V1-V2-V4-V5, with states V3 and V6 omitted.

For the single phase circular operation, switching elements pair S7 and S8 are switched. Additionally, the switching element pairs for each phase are switched at the same time when the transmitting coils and the receiving coil are aligned and not translated. Switching element pairs S1, S3 and S5 are switched at the same time as switching element pairs S2, S4 and S6 are switched at the same time. As depicted in <FIG>, the positive voltage at node n+ occurs when one of the switching element pairs S7 is turned ON (and the other is turned OFF) and the negative voltage at n- occurs when the opposite occurs.

As depicted in <FIG>, a γ-mode is excited. This may occur when the transmitting coils and the receiving coils are aligned (not translated). The switching states include V0 and V7. In some aspects, when the transmitting coils and the receiving coils are not aligned, the switching states may be changed, e.g., the controller changes the switching such that other modes may be excited. For example, for translational misalignment along a vector oriented at <NUM>° from the x-axis, the switches may use states V1-V2-V5-V6.

<FIG> illustrates a system used in testing a coil assembly <NUM> in accordance with aspects of the disclosure. The design uses three 1200V/325A SiC half-bridge modules <NUM> (CAS325M12HM2) (example of inverter <NUM>) and gate drivers <NUM> (CGD15HB62LP) from Wolfspeed (example of controller <NUM>). In <FIG>, the modules <NUM> are located below the Phase outputs AC Busbar <NUM>. Each module <NUM> comprises two switching elements, e.g., S1 and S2. Switching elements S7 and S8 were not used in the testing. An identical unit was used as the rectifier by setting the gate signals to turn the MOSFETs (metal-oxide-semiconductor field-effect transistors) off. A recitifer was used in the receiver instead of an inverter as shown in the figures. Two DC-link capacitors (947D601K901DCRSN) <NUM> are attached to the DC-link busbars <NUM> and one snubber capacitor (SCD305K122C3Z25-F) per module <NUM>. The modules <NUM> was operated in an open-loop fashion from a TMS320F28335 DSP (not shown in <FIG>). The dead-time was set to 600ns. The operating frequency was chosen to achieve zero-voltage switching (ZVS) at full load in the aligned configuration. The operating frequency was <NUM>.

A high voltage battery NHR <NUM> was used as an input <NUM>. The load was an additional high voltage battery NHR <NUM>. The load battery was in parallel with a 14Ohm resistor bank. Oscilloscopes were used to capture waveforms. Specificallty, a Teledyne Lecroy HDO8108 oscilloscope was used to capture the transmitter voltage and current waveforms. A Yokogawa DLM4058 oscilloscope was used to capture the receiver waveforms. The oscilloscopes were operated with independent triggers, resulting in an arbitrary phase shift between the transmitter and receiver plots presented in the following section. A Yokogawa WT1806E power analyzer was used to measure the DC input power, DC output power, and DC-to-DC efficiency of the system.

<FIG> depict the coil configuration for a double layer coil assembly <NUM> used in the experiment and <FIG> depicts an image of the coil assembly. As depicted, the connections are co-planar with the coils. This enables the assembly to be thinner than if the connections were not co-planar. The double layer coil assembly <NUM> has a balanced inductance and a larger coil span.

The coil assembly was <NUM> x <NUM>. The total coil mass including ferrite, Litz wire, and wire guides were <NUM>. The wire was 6AWG type 2litz with a strand gauge of 38AWG produced by New England Wire. The ferrite <NUM> was constructed from Ferroxcube PLT64/<NUM>/<NUM> tiles of 3C94 material.

The distance between surfaces of the transmitter coil assembly and the receiver coil assembly was <NUM>. This is an expected operating gap for a light duty vehicle. Different application may have between air gaps. For example, an air gap for an heavy duty vehicle may be <NUM> or larger.

The electrical parameters were set to achieve a 50kW power transfer at the set distance and a phase current of 73ARMS. This current corresponds to a current density of <NUM>. 5ARMS/mm<NUM> in 6AWG wire. The design was limited by the <NUM> diameter of the Litz wire and the minimum bend radius, which was set to be five times the diameter. A minimum wall thickness of <NUM> for mechanical integrity of the additively manufactured wire guides also limited space for additional amp-turns. The resulting system has a transmiter clearance of <NUM> and a magnetic airgap of <NUM>, e.g., between transmtter coils and receiver coils.

Three alignment conditions of the transmitter coils and the receiver coils were tested: aligned, aligned with a <NUM>° rotation; and offset <NUM> in both x and y directions as shown in <FIG>. The receiver coil assembly is shown in the figures by dashes whereas the transmitter coil assembly is shown by a solid line. In <FIG>, the receiver coil assembly is translated -<NUM> in the x direction and +<NUM> in the y direction.

Two resonant network topologies were used: YC-YL and YC-ΔL. The compensating capacitance was determined as described herein using equations <NUM> or <NUM>. The capacitance values are shown in <FIG> for each topology in the experiment.

<FIG> illustrates a summary of the experimental results for the YC-YL resonant network topology. As shown in <FIG>, the aligned and <NUM> rotation results are nearly identical due to the rotational invariance of the system when the transmitter coil assembly <NUM> and the receiver coil assembly <NUM> have the central axes aligned. This is an advantage of a polyphase system over a single phase system. Further, both conditions, aligned and aligned but rotated <NUM>° achieve 50kW power transfer with greater than <NUM>% DC-to-DC efficiency. In <FIG> Vdc,g refers to the DC bus voltage of the transmitter and Vdc,v refers to the DC load voltage. Pg,dc refers to the power at the transmitter and Pv,dc refers to power at the receiver. Rdc, v is the load resistance on the receiver side. This resistance servers as the load <NUM>.

<FIG> illustrates a summary of the experimental results for the YC-ΔL resonant network topology. As shown in <FIG>, the aligned and <NUM> ° rotation results are nearly identical due to the rotational invariance of the system when the transmitter coil assembly <NUM> and the receiver coil assembly <NUM> have the central axes aligned. Further, both conditions, aligned and aligned but rotated <NUM>° achieve 50kW power transfer with greater than <NUM>% DC-to-DC efficiency. The results for the both conditions are nearly the same.

Compared to a YC-YL resonant network, a YC- ΔL configured system is slightly less efficient. This is because the load impedance required to achieve near-unity voltage gain is about three times less than in the YC-YL case, the inverter and rectifier conduction losses are likely much higher in this configuration. The increase in conduction losses may be partially offset by a decrease in switching losses due to a lower DC-link voltage. However, the reduction in switching losses is limited due to ZVS operation of the inverter during turn-on.

As can be seen in both <FIG> and <FIG>, when the transmitter and receiver coil assembly are misaligned in both the x and y axis, the efficiency is reduced. A -<NUM> and <NUM> misalignment represents a worst case scenario. In this configuration, the power transfer capability is limited by the current rating of the coils.

<FIG> illustrates simulation results for various coil assembly topologies which demonstrates the benefit of the disclosed polyphase wireless power transfer systems and transmitter such as a three-phase system.

The simulation included a comparative design study of six different matched coil assembly topologies: <NUM>) single phase unipolar 1ψU,<NUM>) single phase bipolar 2ψB, <NUM>) three-phase unipolar with single phase excitation 3ψU(1ψ), <NUM>) three-phase unipolar with three-phase excitation 3ψU, <NUM>) three-phase bipolar with two layers 3ψB (such as <FIG>), and <NUM>) three-phase bipolar with three layers 3ψB(<NUM>) (such as <FIG>). Matching refers to the transmiting and the receiving coils having the same configuration. To focus on the impact of coil layout, a circular geometry for all the coils assemblies with a fixed outer diameter of <NUM> was used. The coil assemblies use two layers of 6AWG wire except for the three layer three-phase system, which uses 10AWG. This modification was made in attempt to normalize the upper bound of total Litz wire mass and keep the package thickness similar between systems.

In the field of wireless power transfer for vehicles, the system must meet electromagnetic field emission requirements and safety standards. For example, certain requirements and standards are described by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) as referenced by SAE's J2954. For instance SAE J2954 also describes various foreign object heating and ignition tests that a system must pass either through the use of a foreign object detection (FOD) systems or by limiting the maximum flux density on the surface of the transmitter coil assembly. In practice, the peak flux density on the surface of the transmitter coil assembly must be limited to meet the touch safety requirements described in SAE J2954.

Safety considerations with respect to emissions and foreign object heating severely limit the maximum power capability of wireless power transfer systems with a given coil assembly size. The design of the system in the stimulation maximizes the power capability while keeping the peak magnetic field occurring at a distance of <NUM> from the center of the system below <NUM> mT, which is the level specified by ICNIRP for pacemaker compatibility. This is accomplished by adjusting <NUM>) the number of turns and <NUM>) the spacing between the turns. The ferrite <NUM> thickness was adjusted to keep the peak flux-density below <NUM> mT.

Of the single phase excited systems, the bipolar coil assembly was able to achieve the highest power transfer rate under the emissions constraint. This indicates that the bipolar coil assemblies have better emissions characteristics that unipolar assemblies. The assemblies utilizing three-phase excitation are able to achieve higher power levels for these emissions constraints. The bipolar three-phase assemblies combine the uniform emissions profile of the single phase unipolar assembly with the overall lower emissions characteristics of the single phase bipolar assembly.

The three-phase bipolar assemblies achieve better specific power than the single phase bipolar assembly and approach that of the single-phase unipolar assembly. The 3ψB(<NUM>) is nearly as good as the 1ψU topology by this metric. The copper mass of the Litz wire tracks the power rating of the coils fairly closely. Most of the difference in specific power between the topologies can be traced to the mass of the ferrites. The improved specific power of the 1ψU, 3ψB, and 3ψB(<NUM>) couplers can be attributed to the better ferrite utilization of these topologies. In contrast, the 1ψB, 3ψU(1ψ), and 3ψU topologies have prominent regions where the maximum flux density is significantly below the <NUM> mT limit. As a result, the former topologies must have thicker ferrites for a given power to avoid magnetic saturation.

The bipolar three-phase coil assemblies also have better foreign object heating metrics. The magnetic fields on the surface of the coil assemblies were stimulated. In the stimulation, it was assumed that the surface is <NUM> from the ferrites <NUM>. The parameter examined with P/Bmax. P is the power transfer and Bmax is the peak flux density on the surface. <MAT> is proportional to the amount of eddy-current heating that would occur in a small metallic object placed on the surface at the maximum flux density location. Larger values of this ratio indicate that a given system should be capable of transferring more power before reaching foreign object heating and touch safety limitations.

As shown in <FIG>, 3ψB topology has the best performance by this metric, with a ratio of <NUM>. This topology is followed closely by the 3ψB(<NUM>) topology at <NUM>. These designs exhibits a more uniform surface flux distibution which improves P/Bmax.

The 3ψB(<NUM>) topology achieved a high specific power density of <NUM> kW kg-<NUM>. However, since in the three layer design, the wire gauge was decreased to keep the total thickness relatively constant, there was an increase in coil voltage to achieve the same power. In practice, the maximum permissible coil voltage may be limited for safety. If this is the case, using the 3ψB(<NUM>) topology may require the coil thickness to increase by <NUM>% beyond the 3ψB topology (two layer). This consideration must be weighed against the potential for improving power density and specific power when using the 3ψB(<NUM>) design.

Various aspects of the present disclosure may be embodied as a program, software, or computer instructions embodied or stored in a computer or machine usable or readable medium, or a group of media which causes the computer or machine to perform the steps of the method when executed on the computer, controller, and/or machine, although this subject-matter, included in the description because of illustrative purposes, is not part of the claimed scope of the invention. A program storage device readable by a machine, e.g., a computer readable medium, tangibly embodying a program of instructions executable by the machine to perform various functionalities and methods described in the present disclosure is also provided, e.g., a computer program product.

The computer readable medium could be a computer readable storage device or a computer readable signal medium. A computer readable storage device, may be, for example, a magnetic, optical, electronic, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing; however, the computer readable storage device is not limited to these examples except a computer readable storage device excludes computer readable signal medium. Additional examples of the computer readable storage device can include: a portable computer diskette, a hard disk, a magnetic storage device, a portable compact disc read-only memory (CD-ROM), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical storage device, or any appropriate combination of the foregoing; however, the computer readable storage device is also not limited to these examples. Any tangible medium that can contain, or store, a program for use by or in connection with an instruction execution system, apparatus, or device could be a computer readable storage device.

A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, such as, but not limited to, in baseband or as part of a carrier wave. A propagated signal may take any of a plurality of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium (exclusive of computer readable storage device) that can communicate, propagate, or transport a program for use by or in connection with a system, apparatus, or device. Program code embodied on a computer readable signal medium may be transmitted using any appropriate medium, including but not limited to wireless, wired, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

The term "Controller" as may be used in the present disclosure may include a variety of combinations of fixed and/or portable computer hardware, software, peripherals, and storage devices. The "Controller" may include a plurality of individual components that are networked or otherwise linked to perform collaboratively or may include one or more stand-alone components. The hardware and software components of the "Controller" of the present disclosure may include and may be included within fixed and portable devices such as desktop, laptop, and/or server, and network of servers (cloud).

Claim 1:
A three-phase inductive power transfer system comprising:
a transmitter comprising:
a coil assembly (<NUM>) comprising at least one coil associated with each phase; and a
compensating capacitance connected in series with the at least one coil for each phase, the value of the compensating capacitance for each phase being based on the topology of both the compensating capacitance and the at least one coil for the phases, and on the mutual inductance between the at least one coil for each of the phases, such that the transmitter has at least two independently excitable resonant modes at a resonant frequency, wherein the at least two independently excitable resonant modes comprises α-axis and β-axis modes, wherein, in the α-axis mode, maximum flux density is aligned with an area where a pair of coils (A+, A-) for a first phase are located, and wherein, in the β-axis mode, maximum flux density is aligned with an area where pairs of coils (B+, B-, C+, C-) for second and third phases are located.