Analysis and improvement on feedwater control system of 2×142 MW cogenerating units

The feedwater flow control system of 2×142 MW units (each consists of two boilers and one turbine) in Chengdu Cogeneration Power Plant is introduced. Since the turbine-driven feedwater pump failed to regulate directly the drum level of single boiler and problems like pressure overrun of main feedwater pipe existed, DCS was utilized to solve the problems for its features of shared information, powerful configuration functions and easy modification. Without adding hardware, a control loop for drum level regulation of single boiler by turbine-driven feedwater pump and a control loop for main feedwater pipe over and under pressure protection were added through software configuration, which realized automatic feedwater flow control under two operation modes of one boiler to one turbine and two boilers to one turbine while settling the pressure protection of main feedwater pipe and raising the security and reliability of the units.