Wireless Charging of Electric Vehicles – a Pareto-Based Comparison of Power Electronic Topologies

Systems for contactless inductive power transfer are likely to be one of the future charging technologies for electric vehicles. Even though the technology itself has already proven to be reliable in a large number of industrial and consumer applications, some effort is still needed to improve the efficiency and reduce costs. Another challenge is the relatively high magnetic air gap and the variable magnetic coupling factor of the contactless transformer due to a possible misplacement of the vehicle on the charging station.

This thesis provides two key contributions to the research field of inductive power transfer. First, a systematic comparison of suitable power electronic topologies is carried out. With the methodological approach of the multi-objective optimization, the design trade-offs, as well as the benefits and drawbacks of each topology are quantified in detail. The second contribution is a novel topology with dual-side power control which significantly increases the efficiency under the conditions of a variable magnetic coupling factor and in partial load.

The validity of the simulation models and the performance of the dual-side controlled topology are confirmed by means of a 3kW hardware prototype. A system efficiency, from the AC grid to the vehicle battery, between 90% and 94% is achieved at air gaps ranging from 100mm to 170mm. The novel dual-side controlled topology thus combines a high system efficiency with a low hardware effort and high robustness.