Research of process immunity time of boiler coal feeding system in thermal power plant and solution to voltage sags

The shutdown of the thermal power plant caused by voltage sags has occurred several times in the whole country. In order to ensure the continuity of power generation during voltage sag, research on process immunity time (PIT) of the boiler coal feeding system is carried out, sensitive equipments in the process which affected by voltage sags and corresponding process parameters are listed, and PIT values and the most sensitive equipment which is coal feeder are obtained. The under-voltage trip of inverter during voltage sag is the real cause of coal feeder shutdown. According to the characteristics of inverter’s AC-DC-AC structure and combining power electronics technology Low Voltage Ride Through (LVRT) systems are researched and developed based on DC support technology which take batteries as energy source. And through BOOST DC/DC converter, the LVRT system outputs a constant DC voltage, supporting inverter’s DC bus. Experimental data and field applications show that the LVRT system can ensure the normal operation of inverter during voltage sag which ensures the safe and stable operation of the boiler coal feeding system and the continuity of the power generation process.