The energy feedback will be used for AC400V load or backtracked to the 35kV power grid. The feed-in system can judge whether there is a train in the regenerative electrical braking state on the DC grid according to the signal detected by each sensor. Once the train is in the regenerative braking state and needs to absorb energy, the system starts the absorption process.

Setting the judgment reference value in the control system, when the bus voltage is greater than the reference value, first input the inverter absorption function of the feed-in device, the inverter absorption transfer DC power generated by train braking into electrical energy, and then through the isolation transformer boost to AC35kV voltage, automatic tracking AC35kV bus voltage, and supply load to the medium voltage power, to use the renewable energy in the electrical equipment.

With the rise of network voltage pressure, the feed-in system can be increased from 0 to full power absorption status. The absorbed power of feeding system is set to be greater than the regenerative energy of train braking. In the process of net voltage rising, the feeding system has sufficient energy to absorb and stabilize the traction network voltage, to ensure that the subway train is fully and effectively using electric braking.