A Three-Stage Optimization Strategy for Techno-Economic Operation of Railway Flexible Traction Substation

The railway flexible traction substation (FTSS) with integrations of railway power flow conditioner (RPFC), photovoltaic (PV), and energy storage system (ESS) have great potential for achieving objectives including efficient energy utilization, cost saving, and power quality improvement. However, the uncertainties of both PV generation and traction load impair FTSS operation, posing challenges in fully exploiting flexibility for realizing these objectives. Therefore, this paper proposes a three-stage strategy to optimize the operation cost and power quality performance of FTSS against uncertainties. In the first stage, a day-ahead optimization model is established to plan the ESS charging/discharging to minimize daily operational costs. The second stage, intra-day optimization, corrects the ESS plan according to the forecast errors, where an adaptive weight coefficients-based model predictive control method is proposed to obtain a better economy. The third stage implements real-time power quality improvement, aiming to instantaneously suppress negative sequence current by fully utilizing the RPFC capacity. Numerical studies show that the proposed method presents better performance on daily cost reduction and negative sequence current suppression of FTSS than existing methods.