Implementation of an Active Regeneration Unit in a traction substation

This paper describes the practical implementation of an Active Regeneration Unit (ARU) at two locations of the metro network in Rotterdam. Surplus braking energy that cannot be used by other vehicles is supplied back into the public grid. Optimal locations for the regeneration units are determined by simulations based on the complete infrastructure, the vehicles characteristics and the operational timetable. The amount of regenerated energy is very dependent on the location. Locations with an average density of traffic seem to offer the most potential for energy regeneration. The simulations show that up to 19% of the energy normally used over a daily timetable can be regenerated. With increased converter power values of up to 23% can be achieved. The regeneration range is limited to a voltage range between the zero-load voltage of the transformer-rectifier and the regeneration voltage limit. Regeneration is further limited by the voltage drop over the contact line and the return path. Therefore, an increase of the regeneration limit is proposed. Several further implementation issues are discussed. These include: the space required for the ARU; the electrical connection to the rectifier; and the protection philosophy to protect the ARU from external disturbances whilst ensuring the maximum availability of the infrastructure. As the ARU will be connected to the existing installation in the substation, it is important to verify the influence from ARU generated transients and harmonics on the existing installation in a simulation of the complete system.