Apparatus and a method for wireless transmission of power between DC voltage sources

#This application is a National Phase Entry under 35 USC § 371 of PCT Patent Application Serial No. PCT/NO2016/050006 filed Jan. 19, 2016, which claims priority to Norwegian Patent Application No. 20150087, filed Jan. 19, 2015, the disclosure of each of these applications is expressly incorporated herein by reference in their entirety.

#The present invention relates to the field of inductive power transmission between two structures that are moving with respect to each other, resulting in variable coupling. In particular, it is disclosed an apparatus for wireless transmission of controllable power from a DC voltage source to a DC voltage load.

#Whenever two current-conducting coils are placed in space so that the magnetic field generated by each of them is also linked to the other, electrical energy transfer can take place; such form of transfer is normally termed as Inductive Power Transfer (IPT).

#In order to make the invention more readily understandable, the discussion that follows will refer to the accompanying drawings, in which

#FIG. 1 is a schematic representing a wireless power transfer apparatus with series-connected resonant capacitors, and its main components,

#FIG. 2 is the schematic of an H-bridge circuit used as inverter, including four IGBT switching devices and a smoothing capacitor on the DC-side,

#The present invention relates to wireless power transfer, and in particular to wireless power transfer where the coupling coefficient varies, that is where primary and secondary coils are loosely coupled. Such arrangements may find wide fields of application.

#In the following discussion, it will be adhered to the accompanying drawings; however the drawings do not necessarily disclose all features/components, moreover the components shown in the drawings are not mandatory. The drawings are meant to ease understanding of the present invention.

#It shall be appreciated that by loosely coupled there is no restriction on the relative movement: i.e. full 6-degrees of freedom (x-y-z, roll, pitch, yaw) are allowed, as the parameters affecting power flow equations are the resulting magnetic coefficients (self-inductances and coupling coefficient). For the same reason, it is not important whether it is the primary or secondary coil (or both) that is moving. The only constraint on the speed of movement is that it must be much slower that the time-frame corresponding to the electrical resonant frequency of the system. This is however satisfied in most practical cases.