Governments have recently been dedicating relevant funds to cope up with the inevitable transition to sustainable mobility aiming for a greener transportation sector. This scenario is backed up by the deteriorating global energy crisis which is predicted to hasten the transition to sustainable energy. Focus has been given to railway systems being globally considered as a tractor project for promoting the use of green and renewable energy by helping build the required infrastructure. As a result, a high tendency for integrating onboard energy storage systems in trains is being observed worldwide. This paper provides a detailed review of onboard railway systems with energy storage devices. In-service trains as well as relevant prototypes are presented and their characteristics are analyzed. A comprehensive study of the traction system structure of these vehicles is introduced providing an overview of all converter architectures used, categorized based on the type of onboard energy storage device on the train. The current situation of hydrogen fuel cells in railway systems is presented as well, highlighting consistent tendencies. The paper also provides a glimpse into commercial battery and fuel cell products used on operating trains.

The prediction of the driving cycle (vehicle speed profile versus time) and the road grade cycle (road grade profile versus time) can improve a variety of vehicle functions, especially the energy management of HEVs and PHEVs. The variability of the driving conditions (environment) together with the nonlinear and variable driver behaviour (driving style) makes the driving cycle `on-board & real-time' prediction a highly complex task. This paper proposes an intelligent technique for the real time prediction of the vehicle speed and road grade profiles for the (selected) time horizon whilst the vehicle is in route. The proposed method uses an Artificial Neural Network which processes both the vehicle speed measurement (current and previous data samples) and some information related to the driving conditions present in the route, which could be obtained in advance from the new generation of vehicle navigation systems. The driving cycle and road grade on-board predictions allow the energy management system of HEV/PHEVs to achieve further reductions of fuel consumptions.

Electric propulsion and integrated hybrid power systems can improve the energy efficiency and fuel consumption of different kinds of vessels. If the vessel power system is based on DC grid distribution, some benefits such as higher generator efficiency and lower volume and cost can be achieved. However, some challenges remain in terms of protection devices for this kind of DC grid-based power system. The absence of natural zero crossing in the DC current together with the fast and programmable breaking times required make it challenging. There are several papers related to DC breaker topologies and their role in DC grids; however, it is not easy to find comprehensive information about the design process of the DC breaker itself. In this paper, the basis for the design of a DC solid-state circuit breaker (SSCB) for low voltage vessel DC grids is presented. The proposed SSCB full-scale prototype detects and opens the fault in less than 3 µs. This paper includes theoretical analyses, design guidelines, modeling and simulation, and experimental results.

The benefits of using Power Electronics Based DC Distribution Systems in electrically propelled vessels are well known. However, some aspects must be deeply analyzed to guarantee a safe, robust and stable system by design. This paper presents a multivariable DC Distribution System mathematical model, where all the transmission lines and filters impedances are considered. The model has been tackled under a holistic approach in which the average small-signal model of the drives/converters can be easily added and ‘connected’ to the main grid model. The stability and power quality analysis, as well as the design and tuning of controls and active damping strategies can be conducted through this mathematical model at low computational cost. In this paper, the usefulness of this model in the early design stages is presented through its application over a realistic design scenario. Moreover, the performance of the proposed model is proven into a real test bench, which presents a configuration and architecture quite close to the one used in a real vessel. The carried out tests prove the suitability of the proposed model, becoming a significant tool to get an improved design.