Study On Regenerative Braking Efficiency For Electric Vehicles Based On The Xi’an Driving Cycle

Developing EV(electric vehicle) can relieve energy and environment issues greatly. But EV still has its fatal flaw, the short driving range, which affects its popularization. Improve the battery’s specific energy is the most effective way to increase driving range, but restricted technology, battery technology is difficult to achieve a breakthrough in the short term. Extend the driving range mainly depends on improving the energy efficiency of battery. The key technology is to develop a better performance, more efficient regenerative braking system, which can change the car’s mechanical energy to electrical energy and store it in the battery. The regenerative braking of electric vehicle not only effects by the vehicle parameters, the system’s own structure, the control strategies and other factors, but also effects by the driving cycle. Especially in urban conditions, with serious traffic congestion, cars run in lower average speed, and it also requires multiple starts and stops, which cause a lot of braking energy waste. The subject based on the basic research projects of central universities fund, “the research of test automobile of pure EV” and “the research of powertrain matching and critical control for EV”. This paper focuses on the operating characteristics of cars and major components and the regenerative braking efficiency of EV when it runs in Xi’an driving cycle. Main research are as follows:(1) Design and conduct road tests in Xi’an, build the Xi’an driving cycle model based on the road test data.(2) Analyze the braking process of EV, describe the basic principles of regenerative braking and several major factors which affect its efficiency.(3) Based on ADVISOR’s own regenerative braking control strategy, combine with the factors, propose the control strategies which used in the simulation model of this paper.(4) Construct the vehicle model and major component model by ADVISOR, import the Xi’an driving cycle into ADVISOR, make the car run in Xi’an driving cycle, obtain the operating characteristic curve of vehicle and major component and the simulation data of regenerative braking efficiency. At last, analyze and evaluate the simulation output results in detail.The research work has some practical significance for operating and promoting of EV in Xi’an driving cycle.