Author(s)

WENLI DENG, CHAOHUA DAI, HANBO ZHANG, MI LI

Abstract

With the rapid development of high-speed and heavy-haul railways around the world, how to realize energy saving and emission reduction has been a huge challenge to promote the green development of the railway system by fully utilizing existing resources (such as idle-land resources and solar energy along the railway). This paper proposes an eco-sustainable photovoltaic/energy storage system (PV/ESS) integrated into AC two-phase traction power supply system (TPSS) of electrified railway. Based on the proposed topology, a hierarchical optimization control method is also presented. Concretely, in the system layer, the energy management strategy considering triple random fluctuations (i.e., the real-time power of PV system and two-phase independent traction loads) is designed to prevent PV power flow reverse transmission and improve the utilization rate of PV energy. In the converter layer, besides the conventional maximum power point tracking (MPPT) control of boost converter, a dual-loop state-decoupling control strategy of PV inverter is adopted to ensure the effective power exchange between PV side and traction side. At the same time, the internal coordination control strategy of bidirectional DC/DC converter is detailed elaborately to enhance the long-term operational ability of ESS. Thereafter, to assess the utilization rate of PV energy and carbon emission reduction effect of TPSS under the long-time scale, the mathematical models of PV power estimation and carbon emission reduction are established, respectively. Finally, based on the typical working conditions and the measured loads/external meteorological data from a traction substation in China railway, the technical feasibility of the proposed system and hierarchical optimization control is validated.

Keywords

energy storage system, feasibility verification, photovoltaic power generation, traction power supply system, hierarchical optimization control