A multi-hybrid energy system for hybrid electric vehicles

Recently the thermoelectric-photovoltaic (TE-PV) hybrid energy system for hybrid electric vehicles has been proposed. However, the output voltage of this TE-PV hybrid energy system is governed by the voltage of the battery, which is affected by the state of charge of the battery and the charging/discharging current. Furthermore, in order to improve the power density and life cycle of the battery, the ultracapacitor (UC) has been proposed to hybridize with the battery to form a hybrid energy storage system. In this paper, a multi-hybrid energy system is proposed for HEVs, which incorporates the advantages of the TE-PV hybrid subsystem and the ultracapacitor-battery (UC-B) hybrid subsystem. On the one side, the TE-PV hybrid subsystem can provide the higher fuel economy due to the increase of onboard renewable energy, the better energy security due to the use of multiple energy sources, and the higher control flexibility due to the coordination for charging the same pack of batteries. On the other side, the UC-B hybrid subsystem can provide faster transient power, higher power density and longer battery lifetime. Detailed simulations results are given to highlight the effectiveness of the designed multi-hybrid energy system.