Electric vehicle detection for roadway wireless power transfer

Abstract

A method of detecting a wirelessly powered vehicle on a roadway uses detection of induced voltages or currents in coils provided in the roadway. Once the vehicle has been detected the appropriate coils can be energised to power the vehicle.

1 . A method for supplying power to a vehicle on a path or roadway comprising a plurality of wireless power transfer coils, the method comprising:
 detecting a current or voltage induced in a de-energised wireless power transfer coil; and   energising the wireless power transfer coil dependent on a property of the induced current or voltage to make power available to the vehicle.   
     
     
         2 . The method as claimed in  claim 1  wherein the induced current or voltage is resonant. 
     
     
         3 . The method as claimed in  claim 1  wherein the current or voltage is induced in the de-energised coil from energisation of a neighbouring coil. 
     
     
         4 . The method as claimed in  claim 1  wherein the current or voltage is induced in the de-energised wireless power transfer coil by the vehicle providing a magnetic path from a neighbouring energised wireless power transfer coil. 
     
     
         5 . The method as claimed in  claim 1  wherein the current or voltage is induced in the de-energised wireless power transfer coil by a magnetic field produced by the vehicle. 
     
     
         6 . The method as claimed in any  claim 1  comprising a step of opening or closing a switch to make the de-energised wireless power transfer coil resonant at a required frequency such that the induced current or voltage is resonant. 
     
     
         7 . The method as claimed in  claim 6  comprising operating the switch at intervals to allow sampling of the induced current or voltage. 
     
     
         8 . The method as claimed in  claim 1  wherein the property of the induced current or voltage may comprise magnitude or change in magnitude of the induced current or voltage. 
     
     
         9 . A wireless power transfer apparatus for providing a magnetic field to wirelessly power a vehicle on a path or roadway comprising a plurality of wireless power transfer coils, the apparatus comprising:
 a switch associated with each coil to selectively energise the coil to make power available to the vehicle, or de-energise the coil;   a current detector associated with each coil for detecting a current induced in the coil when the coil is de-energised; and   a controller to control the switch to energise the coil dependent on an output of the current detector.   
     
     
         10 . The wireless power transfer apparatus as claimed in  claim 9  wherein the controller is operable to make the de-energised coil resonant at a required frequency such that the induced current is resonant. 
     
     
         11 . The wireless power transfer apparatus as claimed in  claim 10  wherein detection of the induced current further comprises sampling of the induced current. 
     
     
         12 . The wireless power transfer apparatus as claimed in  claim 11  wherein the controller is operable to provide a de-energised tuned coil in a first state to allow the induced current to resonate, and a second state to allow the induced current to be non-resonant. 
     
     
         13 . The wireless power transfer apparatus as claimed in  claim 9  wherein the controller energises the coil dependent on the magnitude of the induced current. 
     
     
         14 . The vehicle detection apparatus as claimed in  claim 22  wherein the change in coupling is detected by detecting an induced signal. 
     
     
         15 . The vehicle detection apparatus as claimed in  claim 14  wherein the induced signal is a resonant current or voltage. 
     
     
         16 . The vehicle detection apparatus as claimed in  claim 15  wherein the detection circuit is operable to make a de-energised module resonant at a required frequency such that the induced current or voltage is resonant. 
     
     
         17 . The vehicle detection apparatus as claimed in  claim 15  wherein the detection circuit samples the induced current or voltage. 
     
     
         18 . The vehicle detection apparatus as claimed in  claim 15  wherein the detection circuit is operable to provide a de-energised module in a first state to allow the induced current or voltage to resonate, and a second state to allow the induced current or voltage to be non-resonant. 
     
     
         19 . The vehicle detection apparatus as claimed in  claim 15  wherein the detection circuit is operable to energise the module dependent on the magnitude of the induced current or voltage. 
     
     
         20 - 21 . (canceled) 
     
     
         22 . The method of  claim 4 , further comprising:
 detecting a current or voltage induced in an energized wireless power transfer coil, and   deenergizing the wireless power transfer coil dependent on a property of the induced magnetic filed in the energized wireless power transfer coil.