Study On The Reform Of Preventing LVRT For Powder Feeder Inverter In Thermal Power Plant

To meet the demand for energy saving and consumption reduction, the inverter with its superior speed governing performance has been widely used in thermal power plant auxiliary equipment design. But because of the high sensitivity of inverter, when voltage dip occurs in the power grid or auxiliary supply system, the low voltage tripping of inverter will be caused. However, the key auxiliary equipment of thermal power plant tripping will lead to the unit shutdown and cause damage to the production safety. It will have a direct impact on the safety and continuity of production, and also cause serious economic losses and equipment damage to enterprises. The problem of the inverter without low voltage ride through (LVRT) capability has been widely concerned. Single unit capacity of thermal power plant is bigger, the impact and threat to the safe and stable operation of power network will be even greater because of the thermal power unit auxiliary equipment without LVRT capability. The problem of thermal power unit auxiliary without the LVRT capability is widespread throughout the country. The problem of the thermal power unit shutdown caused by low voltage has been attracted high attention to Power Grid Corps. The powder feeder is one of the important auxiliary equipment in thermal power plant. Unplanned shutdown caused by the low voltage tripping of powder feeder inverter has brought great economic losses to the power plant, and it is also a major security risk in thermal power plant operation. So the reform of improving LVRT capability of powder feeder inverter in thermal power plant has important significance for the safe and stable operation of thermal power plant.In this paper, according to the problem of unit shutdown in a thermal power plant caused by the impact of LVRT on powder feeder inverter, the power supply mode of powder feeder inverter, the reasons for low voltage in thermal power plant, and the reasons for the low voltage tripping of the inverter are analyzed. By comparing the current measures for restraining the low voltage tripping of powder feeder inverter, SGS system based on the technology of DC-bank has been selected to use for the reform of powder feeder inverter. According to the actual situation to make the installation scheme, through the analysis of system composition, working principle and functions, and the test of short interruptions, dual power switching and Main Fuel Trip (MFT) action, it is proved that the SGS system can make the powder feeder inverter have LVRT capability, the problem of low voltage tripping of the inverter is completely solved, the normal operation of the powder feeder is maintained during the low voltage, unplanned unit shutdown is avoided, and the safe and stable operation of the power grid and units is ensured.