Many DC energy solutions have emerged as potential candidates to enhance the electrical infrastructure in a localized approach, allowing future expansion in the transportation sector despite the congestion of the utility grid. However, the risk of designing large power converter units as controllable substations in complex networks, such as electric railway systems, has encouraged the sophistication of modeling and testing tools. This paper presents a high-fidelity, real-time model implementation of a controllable substation for DC traction power systems. This representative model is developed to facilitate the testing of different upgrading options to understand and quantify how these changes will affect the system and, more importantly, which features are critical to further increasing the sustainability of the railways. This is applied to a case study of the Dutch railway system in Wierden. It is found that while controllable substations can reduce voltage drops from an average of 400 V to only about 230 V, the benefit they bring in regenerative braking harvesting does not outweigh the investment costs, calling for further investigation of energy storage systems as another potential solution.

DC energy hubs have emerged as suitable candidates to enhance the electrical infrastructure in a localized approach, allowing future expansion in the transportation sector despite the electricity grid congestion. However, a risk in designing such a hub is that the outcome of the optimization can be a mere consequence of the (lack of) sophistication of its generation and load models. In that aim, this paper presents a sensitivity analysis for a power demand profile for a DC railway traction power substation, taking into account traction power parameters and the heating, ventilation, and air conditioning (HVAC) modeling approaches. It is found that the traction parameters such as total mass can be confidently considered using an averaged value. On the other hand, modeling the HVAC system using an averaged power demand can lead to errors over 6%, especially in the recovered braking energy calculations.

This paper proposes an interleaved partial power converter (PPC) for the DC-DC conversion stage of electric vehicles (EVs) fast charging stations. The proposed converter topology is based on the H-bridge DC-DC converter. PPC allows the converter to process only a fraction of the total power, the rest being bypassed and directly supplied to the load. This increases the converter efficiency, as only a portion of the power goes through the converter, thus increasing its efficiency. The principle of operation of the proposed PPC is theoretically analyzed. Simulations of the behavior of the proposed PPC are provided for the charging of an EV battery. Results show the good behavior of the proposed system. It is in particular verified that the proposed converter only process a fraction of the power around 36% for the entire output power range. Comparison with a classical full power converter is provided showing that the proposed topology leads to a significant improvement in terms of conversion efficiency, from 95.1% to 98.3%.