The novel hybrid energy storing unit design for hybrid excavator by the effective integration of ultracapacitor and battery

Ultracapacitor (UC) and battery are two main kinds of Energy Storing Elements (ESEs) used in hybrid vehicles and construction machineries. By a comparison, UC can achieve higher power density and faster charging and discharging speed, while battery owns higher energy density. Based on the complicated working condition of the hydraulic excavator, the novel Energy Storing Unit (ESU) is designed by the effective integration of UC and battery to achieve both of their advantages. The modeling and control strategy of the proposed hybrid powertrain system are developed. Simulation results show the proposed ESU can effectively decrease the fluctuation of the UC SOC and the battery current, which are serious by separated use. As such, the fuel consumption is saved and the battery life is largely extended.