Double-Coupled Systems for IPT Roadway Applications

Dynamic powering of in-motion electric vehicles (EVs) using inductive power transfer (IPT) can potentially solve many of the problems currently faced by EVs: in particular range, cost, and charging rate. However, there is currently limited research focused on suitable IPT primary supply-side infrastructure for such roadway IPT systems, and most proposed systems so far have limitations that affect their usefulness and/or suitability. This paper presents a new roadway IPT system using a double-coupled system that can largely resolve these limitations. The proposed system introduces an intermediary coupler circuit (ICC) with frequency changing capability between the power supply primary track and each ground transmitter pad/coil arrangement. Individual charging sections on the roadway can be controlled independently using the ICCs and only turned ON when required, and as such minimize unwanted magnetic leakage fields. The proposed system provides isolation between the power supply and all of the ground transmitter pads, and allows the power supply to run at a lower frequency while the power transfer takes place at a higher frequency. The system can also potentially reduce the impact of dynamic EV charging on the electrical grid at the times of traffic congestion. A laboratory scale prototype system has been constructed and tested. The intermediary coupler achieved an efficiency of 92.5% at an output power of 5 kW with full system operability.