Study on system efficiency and power flow optimization for dual-mode hybrid electric vehicle

Research and/or Engineering Questions/Objective: Most research of the power-split hybrid vehicle haven't taken the efficiency of the planetary-gear system which changes according to the gear ratio into account and merely consider the power lose based on the mechanical-electric energy conversion and determined the control strategy. The objective of the study is to achieve optimized management and cooperative control of the power flow by building an exact model of hybrid power system and analyzing the efficiency. Methodology: The mechanical loss of the Dual-mode coupling mechanism planetary system is caused by gear mesh, clutch friction, oil seal and bearings. The loss has intimated connection with the parameters of the system status. This chapter has studied the relationship between system parameters and transmission efficiency of planetary transmission in coupling system. It also has built the efficiency model of the planetary transmission in coupling system and amend the model by test. Build a comprehensive efficiency model of the hybrid vehicle, by considering the power loss of engine, battery, motor and other components and mechanical loss of planetary transmission in coupling system, and this model reflects the distribution of the system power flow. So we could achieve the optimized control of system power flow under the requirement of the driver. Results: The planetary transmission efficiency and hybrid vehicle comprehensive efficiency has been described by the functions of system power flow distribution status. By considering of the equivalence relations between battery pack charge/discharge and engine fuel consumption, this chapter has built the optimized model of system power flow control. Limitations of this study: An important limitation of the current study is the calculating of the drag losses of the clutch/brake at very high rotating speed, and the designing of the test bench which should has the ability to measured more than one motor power accurately. So specialize tests of component and corresponding testing equipments are needed. What does the chapter offer that is new in the field including in comparison to other work by the authors: The modelling of planetary transmission efficiency of power coupling system in the dual-mode hybrid system is new. Conclusions: By studying the system efficiency not only revealing how the system works of the system but also guiding the optimize management of the system power flow.