Range extender optimisation for electrical vehicles

Electrical vehicles are disposing innovative drive systems but generally still rely on chemical batteries for power supply with their high mass and low stored energy. With e.g. the rugged lead-acid batteries, the covered ranges are about 50 to 100 km, and this is usually not enough to cover a typical transfer distance between the location of e.g. maintenance and the location of operation. Hybrid vehicles have the opportunity of running by means of the combustion engine and can cover long ranges but have to transport all the time the excessive mass and are much more expensive than electrical vehicles. Mountable range extenders are a flexible solution to increase the transfer range of a pure electrical vehicle. A range extender is composed of a thermo-dynamical machine driving an AC generator and a power conversion circuit to transfer the power into the DC battery circuit. For cost reasons, existing range extenders use standard emergency power supplies delivering 50 Hz in single-phase or three-phase circuits (higher power output). For the conversion of AC into battery level DC various circuit topologies are feasible. These topologies are evaluated with respect to weight, cost, losses. An optimised circuit design is composed of a higher frequency power conversion system using power electronics. The optimised configuration is described in this paper.