A Novel Control Strategy for an Interior Permanent Magnet Synchronous Machine of a Hybrid Hydraulic Excavator

Abstract

A hybrid power train system, which uses an electric machine to balance fluctuations of a load, is a practicable method to improve the efficiency of hydraulic excavators. To realize fast charge and discharge, ultra-capacitors are applied to a hybrid hydraulic excavator (HHE), which will cause the direct current (dc) supply voltage to change in a wide range. When the voltage of the ultra-capacitor varies, the output torque of the electric machine will be affected. In this paper, an interior permanent magnet synchronous machine (IPMSM) is employed in the HHE. When the dc supply voltage is low, the output torque of the IPMSM will drop and cannot balance fluctuations of the load adequately. To improve the control performance of the IPMSM output torque, a novel high-performance control strategy based on a vector control is proposed for the IPMSM to reduce the influence from the dc voltage. The mutual influence between the torque of the IPMSM and the dc voltage is analyzed. The novel high-performance control strategy for the IPMSM is introduced. To verify the effectiveness of the novel control strategy for the IPMSM, simulations and experiments are carried out. The results show that the proposed control strategy can improve the control performance of the IPMSM.