Impedance Based Design Method for Interoperable Wireless Power Transfer Systems

The recently published standard for wireless power transfer for electric vehicles (EV) from SAE provides an impedance based approach to describe and ensure interoperability between the primary and secondary side. This paper extends and utilizes this approach to derive a powerful and flexible design method for interoperable WPT systems. Operational boundaries for the electronics and coils are used to establish an impedance capability range at each interface, which then can be transferred to any other interface and used as a design space, or for assessing a component. This method can be used in various ways, one of which is presented as a process to derive early stage inverter requirements for an interoperable primary system. Furthermore, the method is used to show that the magnetics of the reference primary system in the standard requires active tuning in order to achieve full interoperability at the middle range air-gap class.