Traction inverter system with Lithium-ion batteries for EMUs

Traction inverter system with Lithium-ion batteries for electric multiple units (EMUs) is developed in order to utilize the regenerative electric energy and to reduce peak power at substations. In the system, Lithium-ion batteries unit is connected to the DC link of the traction system in parallel via the DC-DC converter which controls storing and supplying battery power. In powering mode of the train, this system reduces peak power at substations by supplying electric power from the batteries unit. In braking mode of the train, this system prevents getting higher of overhead line voltage by storing excess regenerative power, and saves energy consumption by using battery energy for train powering. This system is installed in one of the Seibu 20000 series which are the commuter trains of SEIBU Railway Company. The traction system with Lithium-ion batteries for EMUs has been evaluated in commercial operations on the Seibu Sinjuku Line since October 2013, and it is confirmed that this system can save energy consumption of 26% and peak power at substations is reduced by 13%. This trial in commercial operations is continued until September 2015.