Hybrid Electric Propulsion Systems Report


The main purpose of this report is to investigate and compare the three popular models of hybrid-electric propulsion systems used in today’s vehicles. After examining the three configurations, we came to the following conclusions for each configuration:

The series hybrid configuration is very efficient for stop-and-go driving situations, but it is not well suited to highway driving. Therefore, this configuration is recommended for specialized vehicles that usually operate under urban driving conditions, such as buses and taxis.

The parallel hybrid configuration is the least expensive and uses the fewest components out of the three hybrid configurations. In addition, this configuration is compatible from traditional transmissions and it operates well under highway conditions. These characteristics make the parallel configuration very suitable for integration into an existing vehicle design. The main disadvantage of the parallel system when compared to the other two models is that the other two systems are more efficient under city driving, but the parallel system is still more efficient than a comparable gasoline-only system.

The series-parallel system has the characteristics of both series and parallel configuration, and it is able to maintain optimum performance under both city and highway conditions. Therefore, the series-parallel system is the most versatile and potentially the best performing hybrid configuration. In exchange for these advantages, the series-parallel is more expensive and more difficult to implement than the other two configurations.

The conclusions of this report are formed from only theoretical analysis of each configuration. Therefore, the advantage and disadvantages listed in this report may not actually be reflected in a comparison of production hybrid vehicles, as there are many factors, other than the propulsion system model, that affect the fuel efficiency and performance of a vehicle. Information regarding the performance and specification of production hybrid vehicles can be found in automobile magazines and websites. This report also does not analyze the components of each configuration in detail due to time and length constraints. A very thorough analysis of hybrid vehicle components and design is provided in the book Hybrid Vehicle Propulsion by C. M. Jefferson and R. H. Barnard.


Hodkinson, R. & Fenton, J. (2001). Lightweight Electric/Hybrid Vehicle Design. United Kingdom: Reed Educational and Professional Publishing Ltd.

Hybrid Center. (2005). Hybrids under the Hood (part 2). Retrieved February 19, 2007, from http://www.hybridcenter.org/hybrid-center-how-hybrid-cars-work-under-the-hood-2.html.

Hybrid Synergy Drive. (2007). Series Parallel Hybrid System. Retrieved February 19, 2007, from http://www.hybridsynergydrive.com/en/series_parallel.html.

Jefferson, C. M. & Barnard, R. H. (2002). Hybrid Vehicle Propulsion. Southampton, United Kingdom: WIT Press.

Kawahashi, A. (2004). A new-generation hybrid electric vehicle and its supporting power semiconductor devices [Electronic Version]. Proceedings of the 16th International Symposium on Power Semiconductor Devices & ICs, 23-29. Retrieved February 19, 2007, from IEEEXplore database.

Miller, J. M. (2004). Propulsion Systems for Hybrid Vehicles. London, United Kingdom: The Institution of Electrical Engineers.

Westbrook, M. H. (2001). The Electric and Hybrid Electric Car. London, United Kingdom: The Institution of Electrical Engineers.

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