Robust energy management of electrified railway traction substation providing secondary frequency regulation

Electrified railways provide innovative insights for providing the secondary frequency regulation (SFR) service to improve grid stability in the net-zero power system. As the role of energy nexus that connects with low-inertia grids and high-power trains, the flexible traction substation (F-TSS) of electrified railway, integrated with power flow controller (PFC) and energy storage (ES) and photovoltaic (PV), with great potential to achieve SFR. However, the current literature lacks a suitable energy management model to portray the capability of SFR services for railways. Meanwhile, the strong uncertainties of PV and traction load pose significant challenges to the safety and economic operation. In this paper, a robust optimization method considering energy-SFR co-dispatch for F-TSS is proposed. Firstly, an F-TSS energy management model is developed to minimize the costs associated with electrical consumption and ES aging, and maximize the profits from SFR response. Secondly, a two-stage robust optimization approach is utilized to crack the uncertainty of traction load and PV output, the PFC control commands and ES charging/discharging strategies are determined in first-stage. In second-stage, the worst-case scenarios are quantified and incorporating feedback into the initial phase for adjustment. Finally, case studies verify the effectiveness of the proposed energy dispatch approach can reduce the overall cost by up to 34 %, as well as provides the SFR response.