Abstract
Energy management strategy influences the power performance and fuel economy of plug-in hybrid electric vehicles greatly. To explore the fuel-saving potential of a plug-in hybrid electric bus (PHEB), this paper searched the global optimal energy management strategy using dynamic programming (DP) algorithm. Firstly, the simplified backward model of the PHEB was built which is necessary for DP algorithm. Then the torque and speed of engine and the torque of motor were selected as the control variables, and the battery state of charge (SOC) was selected as the state variables. The DP solution procedure was listed, and the way was presented to find all possible control variables at every state of each stage in detail. Finally, the appropriate SOC increment is determined after quantizing the state variables, and then the optimal control of long driving distance of a specific driving cycle is replaced with the optimal control of one driving cycle, which reduces the computational time significantly and keeps the precision at the same time. The simulation results show that the fuel economy of the PEHB with the optimal energy management strategy is improved by 53.7% compared with that of the conventional bus, which can be a benchmark for the assessment of other control strategies.
Highlights
In recent years, the problems of energy shortage and environmental pollution have greatly promoted the development of electric vehicles (EVs)
In the PHEVs, in order to make full use of the electricity energy stored in batteries, it is preferred that the battery energy drops to its minimum when the vehicle arrives at the destination
The integrated starter generator (ISG) seldom works under the optimal control based on dynamic programming (DP), but it does not mean that the ISG is useless, because the energy control strategy of the plug-in hybrid electric bus (PHEB) is based on rules in reality, the driving distance is not a fixed value, and the ISG is needed to charge the battery to maintain the state of charge (SOC) level
Summary
The problems of energy shortage and environmental pollution have greatly promoted the development of electric vehicles (EVs). The reference [2] put forward a PHEV rule-based control strategy after considering the all-electric range and charge depletion range operations. The reference [12] studied an optimal energy management of a parallel HEV with the known driving cycle using DP algorithm. The reference [13] built the driving cycle model using traffic information with the help of intelligent transportation systems and utilized the DP algorithm to study the global energy management optimization of a parallel plug-in hybrid electric sport utility vehicle (SUV). The DP algorithm has been proved to be powerful and effective in the global optimization of control strategies in HEVs. In this paper, a global optimization of the energy management strategy for a plug-in series-parallel hybrid bus (PHEB) is explored, and the battery energy state control is specially considered and discussed.
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