Braking energy recuperation for electric traction drive in urban rail transit network based on control supercapacitor energy storage system

Abstract

Braking energy in Electric traction system of electric trains is significant because of trains' frequent accelerating, braking process, so braking energy recovery of urban rail vehicles has been one of the primary objectives in recent years. Energy saving technologies in the railway electric traction field can be mainly divided into two domains: The first one enhances efficiency of traction equipment, such as power electronics converters or traction motors. The other is recovery of kinetic energy in deceleration process of electrified train by applying energy storage devices, or active rectifiers, reversible rectifiers placed to traction substations. The paper presents a regenerative braking energy recovery system based on super-capacitor energy storage system. When electric trains operate in accelerating or braking regimes, the voltage of DC bus will fluctuatesharply to compare with its normal voltage level; therefore, an energy charge /discharge system should be used to not only manage the power flow but also adjust the voltage of the metro contact electric network. For these reasons, super-capacitor energy storage system (SESS) will be integrated to traction motor drive system to recuperate regenerative braking energy in braking phaseand support energy for acceleration phase. Braking energywill be stored in the super capacitors thanks to a bidirectional DC-DC converter interface, and designing control strategy for energy exchange between line utility with traction drive system is to manage UDC-link at a fixed value. At the end, simulation results of the whole system which includes power supply unit, traction motor, driven controller, super-capacitors, Interleaved bidirectional DC-DC converter of line 2 Cat Linh-Ha Dong, Viet Nam have been verified on Matlabsimulink, Simpower system.