The electrified railways in high-altitude mountainous areas are characterized by long and steep slopes, which give rise to two key issues: traction network overvoltage caused by regenerative braking energy (RBE) during downhill sections, and train stalling in uphill sections due to insufficient voltage supply. These challenges pose a threat to train operations. To address the voltage deviation of the traction network and ensure the economical operation of TPSS, this paper proposes an energy management strategy for hybrid energy storage systems (HESS) based on adaptive variational mode decomposition (AVMD). The VMD separates RBE into high and low-power components al-located to batteries and supercapacitors. In this way, the impact of HESS on the voltage level of the traction network and TPSS’s economy is analyzed. Based on the actual data, the decomposition mode number of VMD for RBE and its boundary for high and low-power components is determined, and the economy of the proposed method is verified.