| In a comprehensive literature review,the fundamentals of regenerative braking systems,including its energy management as well as the basics of energy storage systems were discussed.After that,the characteristics of a flywheel energy storage system were illustrated and concurrently dissociated from those of a battery system.Subsequently,the power and energy requirements of the provided Chery vehicle were evaluated for the NEDC.In this process,it was found out that a flywheel storage was neither required for load levelling during acceleration nor during regenerative braking,as the performance characteristics of the installed BESS consistently by far exceeded the peak energy requirements.Following up,a FBESS was nevertheless designed in order to examine if the regenerative efficiency of the Chery vehicle could be thereby enhanced.In the course of the flywheel dimensioning process,the load power during the NEDC was divided into the factors base power and peaking power.The flywheel was designed to provide the peaking power during acceleration and to absorb the total available power during braking.On the other hand,the battery was adapted so that it supplied power up to the base power level to the motor and charged the flywheel otherwise –until a certain SOC was reached– in order to recover its charge lost during high power demand operation.After the FBESS including its controllers was modeled,the regenerative efficiencies of the BESS-and FBESS-based Chery vehicle were calculated.In comparison to the Chery vehicle with a battery storage only,the contribution rate dropped from 7.87 % to 6.84 %,when a flywheel battery system was used.The decrease in regenerative efficiency can be explained by the increased consumed energy that is only partially mitigated by the enhanced regenerated energy in combination with the higher charge and discharge efficiencies of the BESS for the SOC range,battery temperature and discharge rates present during the NEDC. |
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