Rail transit energy feedback 

　　The dynamic energy of the locomotive will be fed back to the DC Overhead Contact Line Equipment (OHE) when the urban rail train brakes at the station, resulting in the increase of the OHE voltage and affecting the safety of the locomotive operation. In the early stage, the resistance dissipation mode was adopted to solve the problem.  When the grid voltage rises, the resistor is switched on to pull down the voltage.  However, this solution brings the following problems:

1. Complete waste of braking energy

2. The heat of the resistance is discharged directly into the tunnel, causing the temperature in the tunnel to rise and increasing the burden of exhaust air in the tunnel.

3. When the resistor absorbs current, the noise is large, which affects the working environment of the workers in the station. 

　　In order to solve the problems caused by the resistance dissipation mode, Beijing IN-Power Electric Co., Ltd. Has introduced the INPCSS and INPEFS series regenerative braking devices.  The INPCSS series device is to store the locomotive dynamic energy in the super capacitor, while the INPEFS series device is to feed the locomotive dynamic energy back to the AC grid side.

A set of INPEFS-2000/35 device is installed in a metro station of Guangzhou Metro, with the AC side voltage of 35KV, and the complete machine power of 2MW.