In recent years, extremely low-temperature weather conditions have resulted in the formation of ice on the contact network of electrified railways, significantly affecting the security of these systems. To address the issue of icing on the overhead contact system, this paper proposes a direct current–based ice melting system. This paper outlines the topological structure of the contact network ice melting system and examines its operational principles. A finite element model was established to investigate the characteristics of the ice melting process on the contact line, and a quantitative analysis was conducted to assess the impact of four critical variables: temperature, ice thickness, direct current, and conductor configuration. Ultimately, a simulation model of the contact line ice melting system for the traction power supply system was developed, and the output/input characteristics of the ice melting system were analyzed to validate its feasibility.

The integration of electric railways with renewable energy sources is crucial for advancing sustainable transportation and building clean, low-carbon, and efficient energy systems in alignment with global sustainable development goals. However, the application of photovoltaic (PV) integration into railway traction power supply systems may exacerbate resonance phenomena between electric locomotives and the traction network. It is therefore necessary to study the impedance frequency characteristics (IFCs) of traction networks to minimize harmonic resonance overvoltage. In this paper, a harmonic impedance model of the sustainable traction power supply system (STPSS) is established, and an impedance analysis method is adopted to reveal the influence law of grid-connected PV inverters on the IFCs of STPSSs. Additionally, to improve the stability of STPSSs, a multi-parameter co-tuning method based on an improved particle swarm optimization algorithm is proposed. This method constructs a multi-objective function that includes resonance frequency, impedance magnitude, and filtering cost, thereby realizing the automatic optimization of the control parameters and filtering parameters of PV inverters. The results demonstrate a 56% reduction in the maximum impedance magnitude within the 0–5 kHz frequency range and a 10.8% cost reduction in the LCL filter implementation, confirming the effectiveness of the proposed optimization model. Results show that the maximum impedance magnitude of the optimized system in the frequency range of 0–5 kHz can be reduced by 56%. Moreover, the cost of LCL filters can be reduced by 10.8% through component value optimization. These findings validate the effectiveness of the proposed method.

Integrating renewable energy systems (RES) and hybrid energy storage systems (HESS) into railway traction power supply systems represents a critical pathway toward low-carbon and sustainable railway transportation as it enables the utilization of clean energy and enhances energy efficiency. However, this integration introduces new harmonic resonance challenges that require systematic analysis. To quantitatively analyze these harmonic resonance issues, this paper studies a flexible cooperative traction power supply system (FCTPSS) integrated with RES and HESS. Based on harmonic transmission theory, mathematical models of harmonic transmission for both the traction power supply system (TPSS) and the FCTPSS are established. Simulation models of the TPSS and FCTPSS are developed in MATLAB2021b/Simulink. Using these simulation models, the harmonic transmission characteristics of the TPSS and FCTPSS are compared and analyzed. The results indicate that the position of the locomotive and the access position of RES and HESS influence the harmonic transmission characteristics. Importantly, integrating RES and HESS shifts the resonant frequency to higher orders and effectively alleviates resonance issues, thereby improving power quality and supporting the reliable operation of sustainable railway systems. These findings offer valuable design guidance for incorporating RES and HESS into traction power supply systems to facilitate the transition toward greener and more sustainable rail transportation.