The Core Control Strategy Adapted to Different AGC Control Modes for Ultra-supercritical Once-through Furnace Unit Burning Lignite

Abstract

As for the once-through unit using lignite, in order to meet the AGC requirements of load change, the coordinated control strategy of unit was optimized. The control strategy was optimized mainly from the aspects of steam temperature control and steam pressure control. In order to control the mid-temperature stability, strategy of using feed water and coal to correct the mid-temperature at the same time was adopted, and the feed water flow was revised by desuperheating water. Different measures including variable parameter control of turbine, rapid coal adding to improve the main steam pressure, and feed-forward adjustment of primary air pressure were taken to improve the delay of main steam pressure, and also shortens the starting time of pressure when changing load. When the unit was put into AGC control, according to the different load changing characteristics of the two modes of BLO and BLR, the variable parameters of the coordinated feedforward of each subsystem were modified. And it is necessary to dynamically adjust the correction factor according to the load fluctuation, in order to reduce disturbance of important parameters such as furnace pressure, main steam pressure, main steam temperature, etc. The application results of the control strategy in the power plant show that the optimized control logic can meet the load regulation requirements of different AGC modes for the lignite burning unit, and the steam temperature and steam pressure control effect is good in the process.