VAR control for inductive power transfer systems
First Claim
1. A method for controlling reactance in the primary conductor of an inductive power transfer (IPT) system, the method comprising:
- sensing a variable reactance in the primary conductor;
switching a first reactive element associated with a resonant circuit inductively coupled with the primary conductor in to the resonant circuit for a first non-zero time period during a first half cycle of a resonant cycle of the resonant circuit; and
switching the first reactive element out of the resonant circuit for a second non-zero time period during the first half cycle of the resonant cycle of the resonant circuit,wherein the first non-zero time period and the second non-zero time period are different time periods, and wherein the first reactive element is switched dependent on the sensed reactance to reflect a controlled compensatory reactance which ameliorates the variable reactance in the primary conductor.
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Accused Products
Abstract
Disclosed herein is an inductive power transfer (IPT) compensation circuit and method for reflecting a controlled reactance to a primary conductor at a selected operating frequency, compensating for reactive loads reflected to the primary conductor by one or more other pick-ups inductively coupled with the primary conductor in use. The compensation circuit comprises a first switch means coupled to a resonant circuit and operable to reflect a capacitive reactance to the primary conductor; a second switch means coupled to the resonant circuit and operable to reflect an inductive reactance to the primary conductor; and control means adapted to control operation of the first and second switch means to compensate for inductive and capacitive reactances, respectively, in the primary conductor.
25 Citations
20 Claims
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1. A method for controlling reactance in the primary conductor of an inductive power transfer (IPT) system, the method comprising:
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sensing a variable reactance in the primary conductor; switching a first reactive element associated with a resonant circuit inductively coupled with the primary conductor in to the resonant circuit for a first non-zero time period during a first half cycle of a resonant cycle of the resonant circuit; and switching the first reactive element out of the resonant circuit for a second non-zero time period during the first half cycle of the resonant cycle of the resonant circuit, wherein the first non-zero time period and the second non-zero time period are different time periods, and wherein the first reactive element is switched dependent on the sensed reactance to reflect a controlled compensatory reactance which ameliorates the variable reactance in the primary conductor. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method comprising:
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measuring a time variable reactance in a primary conductor of an inductive power transfer system, reflecting, from a resonant compensatory device that is loosely coupled with the primary conductor, a time variable compensatory reactance to compensate the measured time variable reactance in the primary conductor, modulating a time, during consecutive resonant cycles of the resonant compensatory device, that a reactive element associated with a tuned pick-up coil of the compensatory device is switched into a circuit with the pick-up coil of the compensatory device, dependent on the sensed reactance, to generate the compensatory reactance, and clamping the voltage across the reactive element associated with the tuned pick-up coil during a portion of the half cycle of the resonant circuit, and unclamping the voltage across the reactive element associated with the tuned pick-up coil during the remainder of the half cycle of the resonant circuit. - View Dependent Claims (9, 10)
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11. A method of operating a resonant wireless power transfer system comprising:
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switching a power supply of the resonant wireless power transfer system at a first frequency to make power available for wireless power transfer from a primary conductor of the resonant wireless power transfer system, wherein the primary conductor is tuned, for an expected load state, to resonate at the first frequency by a first compensation circuit; transferring power wirelessly from the primary conductor to at least one secondary wireless power transfer device that is loosely coupled with the primary conductor, wherein the at least one secondary wireless power transfer device reflects a VAR load onto the primary conductor that causes the resonant wireless power transfer system to operate with a reactive load that is outside to the expected load state; measuring a variable reactance in the primary conductor, caused by the VAR load reflected onto the primary conductor by the at least one secondary wireless power transfer device, while the power supply is switched at the first frequency; compensating the variable reactance in the primary conductor, caused by the VAR load reflected onto the primary conductor by the at least one secondary wireless power transfer device, with a second compensation circuit that reflects a compensatory reactance onto the primary conductor, wherein the second compensation circuit is part of a compensation device that is loosely coupled with the primary conductor; and modulating, with the compensation device, a period of time, during a resonant cycle of the second compensation circuit, that the second compensation circuit is switched to disrupt the action of the second compensation circuit by clamping the resonant current of the second compensation circuit. - View Dependent Claims (12, 13, 14, 15)
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16. A method comprising:
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making power available, for wireless power transfer, from a resonant wireless power transfer primary, wherein the resonant wireless power transfer primary makes the power available at a first frequency; transferring power wirelessly, from the resonant wireless power transfer primary, to at least one resonant wireless power transfer secondary, wherein the at least one resonant wireless power transfer secondary reflects a reactive load onto the resonant wireless power transfer primary that detunes the resonant wireless power transfer primary from the first frequency; sensing a variable reactance, caused by the reactive load reflected by the at least one resonant wireless power transfer secondary, in the resonant wireless power transfer primary; reflecting a VAR load, from a resonant compensation device that is loosely coupled with the resonant wireless power transfer primary, to adaptively retune the resonant wireless power transfer primary to the first frequency; and varying the effective reactance of a reactive element in the resonant compensation device in consecutive resonant cycles to produce the reflected VAR load responsive to the sensed variable reactance by; switching the first reactive element in to the resonant circuit for a first non-zero time period during a first half cycle of the resonant cycle, and switching the first reactive element out of the resonant circuit for a second non-zero time period during the first half cycle of the resonant cycle of the resonant circuit, wherein the first non-zero time period and the second non-zero time period are different time periods. - View Dependent Claims (17, 18, 19, 20)
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Specification