WSEAS TRANSACTIONS on SYSTEMS
(b) Comparison under different drive cycles Fig.13 Comparisons of fuel consumption among HEV with flywheel system, HEV with ultra-capacitor, HEV with chemical batteries and conventional vehicle.
Fig.13 presents the comparisons of fuel consumption among HEV taking different energy storage systems as assistant power. With the same kind of control strategy (Fuzzy logic control) of HEV, the fuel consumption of HEV with FESS is the lowest under different drive cycles (Fig.13.b). For FESS cannot hold a charge for long, HEV taking FESS as its assist power has more advantage of reducing fuel consumption under situation when vehicle is frequently used (public traffics such as taxi or bus). If HEV is put aside for long time, the energy hold in flywheel will gradually exhaust and then there will have some difficulty to restart the engine. So the conception of negative energy storage state could be introduced and the negative value of λ permits the rotary speed of flywheel to be less than its minimal value so that the flywheel is forced to release all the rest energy to start the engine. Besides an accessory 24V battery is also needed to assure the start-up of engine.
1. The energy storage state λ of FESS is adopted for the energy management of vehicle
of FESS are
and the energy characteristics
be suitable for
Jianhui He, Guoqiang Ao, Jinsheng Guo, Ziqiang Chen, Lin Yang
ultra-capacitor, FESS has the longest use-life and the highest energy storage density which also means the smallest mass and the lowest volume. Thus it is more propitious to be installed on HEV. Besides, differing from the SOC of chemical battery and charge state of ultra-capacitor, the energy storage state of FESS can be calculated accurately, which is much helpful to the accurate control of vehicle and is propitious to the practical application of HEV. Furthermore, the fuel consumption of HEV with FESS is the lowest of all. But it also has its disadvantage and the relative high loss of stored energy is an unavoidable factor that confines the performance of FESS. 2. Fuzzy logic controller is adopted for the energy management of HEV, through which both the operating points of ICE and ISG are optimized and the fuel consumption is reduced to greater extent (3.8%) than conventional logic controller.
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Demonstration of attitude control and bus
Applications Conference, pp.2018-2029.
 Zhang Jiancheng, Huang Lipei, Chen Zhiye,
Wu Su. Research on flywheel energy storage
Issue 5, Volume 8, May 2009