Charging Electric Vehicles Using Regenerated Energy from Urban Railways
Nowadays transport system is one of the most important producers of air pollution in cities. Urban railways and electric vehicle will play a fundamental role to accomplish the sustainability of cities. Urban railways are right now an efficient mode of transport. However it is necessary to continue improving its energy efficiency in view of the demand growth. On the other hand, electric vehicles need a charging infrastructure to support their market penetration. In this context, the use of the railway electrical infrastructure to charge electric vehicles could bring several benefits. First of all, there is a cost reduction effect because of the use of an existing installation. Besides, part of the regenerated energy that cannot be accepted by other trains can be used to charge electric vehicles, improving the efficiency of the global system. In this paper, a new system for the global energy management between the railway infrastructure and the electric vehicles is proposed. Besides, the global energy savings that can be obtained using railway electrical infrastructure to charge electric vehicles has been assessed.
7 kW Converter Prototyping for EV Charging Network Development Supplied through Rail Traction Power Systems
― Electric vehicle (EV) charging is expected to impose a high loading demand on distribution systems in near future due to its fast-growing market. This will lead to an urgent need of expensive upgrades on distribution networks if no alternative energy supply is provided. Rail traction power networks benefit from substantial reserve capacity which can be used for this purpose. This paper reports on design, laboratory prototyping, and experimental testing of a 7 kW power electronic converter prototype which can be used for EV charging network development using a single-phase supply emulating AC traction system. The prototype consists of a single-phase voltage source converter (VSC) connected back to back via a DC link, to three half bridge VSCs feeding the charging network. The prototype enables connection of both single-phase and three-phase EV chargers while ensuring balanced three-phase output voltages from the grid forming converter. The converter also offers the possibility of power injection from its DC bus which is useful in DC rail traction application. Additionally, it supports reverse power flow from charging network towards traction substation which is advantageous for voltage support and improved stability of the traction network. Detailed design of main converter components is presented. Experimental results confirm the feasibility and appropriate performance of the studied converter.
Train Coordinated Optimization Operation with Regenerative Braking
Reducing the traction energy consumption plays an important role in railway energy saving. The traditional train optimization operation theories, taking the coasting as the means of energy saving, can't fit complicated lines and is suitable for the single train only. Meanwhile, the highly complicated line will cause the risk of train collision. On the background of the "11th Five-Year" State Science and Technology Support project, a multi-train coordinated optimization operation method based on regenerative braking and safety constraint is studied, and then its application is researched relied on the experimental line. Firstly, a multi-train and multi-object dispatch method for energy saving with safety constraints is researched, and the flexible time constraint model is established. Secondly, on this basis, the multi-train coordinated optimization operation algorithm with the constraints of flexible time and safety is got. At last, the application research is done with the experimental line as the background. The results show that the multi-train coordinated optimization operation method based on regenerative braking, with flexible time and safety constraints, can decrease the energy consumption greatly and improve the traffic volume dramatically in the condition of complicated lines.