Topological Overview of Powertrains for Battery-Powered Vehicles With Range Extenders

The paper presents a topological overview of hybrid powertrains for battery-powered vehicles reinforced by range extenders. First, tradeoffs of employing high energy versus high power battery are revealed. Then, different topologies of battery-ultracapacitor hybrids are discussed, highlighting pros and cons of each configuration. The superiority of fully active hybrids is indicated, obtained at the expense of increase of power electronic circuitry, control effort, and efficiency. The second part of the paper focuses on two types of range extenders: renewable energy and fuel-based units. The operation strategy is shown to be different for each range extender type. The renewable-energy-based range extender should be operated employing either passive or active maximum power point tracking strategy and hence not be involved in the powertrain energy balancing. It is shown that such a strategy allows the rest of system to perceive the renewable energy range extender (RERE) as a part of the load and act accordingly. Solar array is given as an example of a RERE and the possible connection topologies are discussed. On the other hand, the fuel-based range extender (FBRE) should be operated near the lowest specific fuel consumption point employing maximum efficiency point tracking strategy. Fuel cells and internal combustion engines are specified as examples of FBREs. The complete powertrain is shown to resemble a dc microgrid with source, storage, and load units connected through power management circuitry to a common dc link.