Performance of a Series Hybrid Electric Vehicle with a Free-Piston Energy Converter

The free-piston energy converter (FPEC), consists of an internal combustion engine and a linear electrical machine. It is characterised by high efficiency and rapid transient response, which makes it suitable for hybrid electric vehicles. In this paper we investigate the performance gain of utilising the FPEC in a medium sized series hybrid electric vehicle (SHEV), compared to a conventional diesel-generator. First, we utilise optimisation to find a lower limit on the SHEVs fuel consumption for a given drive cycle. In addition, we develop a control strategy based on the ideas of an equivalent consumption minimisation (ECM) proposed earlier in the literature. The results show a potential decrease in fuel consumption of up to 19% compared to a diesel-generator SHEV. The ECM control strategy behaves as desired, and a 13% reduction of fuel consumption compared to a traditional load-following strategy is achieved