Battery storage plant to improve energy saving and security of subway electric supply

摘要

One of the possible actions to improve the management of underground railway plants is the insertion of a battery storage in subway substations. This provides the following main benefits: increase in the recovered braking energy; increase in the system security, as the energy stored in the batteries allows the trains to reach the nearest subway station in case of failure of the main power supply; decrease in the power peak with consequent savings in running and in investment costs; and improvement of the voltage profile on the DC line which produces a decrease in losses. In this paper the operation of a conventional substation equipped with uncontrolled rectifiers is investigated when a device called a Static Watt Compensator (SWC), composed of a battery storage system with a fully controlled DC/DC converter, is connected to the DC bus-bar. A new Battery Supervision System (BSS), tested at the University of Pisa, is used for the on-line estimation of the battery state. For a case study related to the underground of Milan, line 3, a management strategy of the plant and a first economical feasibility are studied.