The load-sensing (LS) system is one of the effective ways to improve energy efficiency of electric wheel loader working function. However, the LS system still has the limitations including throttling loss of control valve, low-efficiency operating points of the electric motor-pump and large installed motor power. Therefore, an electro-hydraulic hybrid variable speed pump drive system (EH-VSPD) is proposed to improve energy efficiency and downsize electric drive system. The system employs a variable-speed pump (VSP) unit to control actuator velocity, avoiding the throttling losses. A high-pressure accumulator in parallel configuration assists the VSP unit under high load condition, to reduce system installed power. The electric VSP unit supplies the average power demand, while the accumulator responds to peak load requirements. An energy management strategy based on the dynamic programming is developed to manage the power distribution of two energy sources. Simulation results show that EH-VSPD system’s energy efficiency is improved from 45.6% to 61.1% and the installed motor power reduces by 44.9% compared to LS system (from 147 to 81 kW). The proposed system achieves a significant improvement in energy efficiency meanwhile downsizing the working function. The performance with different accumulator parameters and installed motor power is also compared to provide a reference for different requirement of system design and loading cycle.
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