Optimization Of Bypass Desuperheating Water Control Strategy On Gas-Steam Combined Cycle Plant

Gas-steam combined cycle power generation technology has been the strong developed in recent years. Compared to traditional coal-fired units, Gas-steam combined cycle units have more flexibility. In the heating season, according to the heat load, combined cycle units can switch conditions in extraction steam, back pressure, all-cut. There is more operating conditions for steam turbine, the regulatory function of bypass is added to more complex. Thus the regulatory function of bypass desuperheating water is facing more complex conditions. In the closed-loop control process, there is a lot of problems, such as: large and fast disturbance, measuring lag, the transfer function of the system is not fixed. Traditional PID regulation has been unable to meet the demand.Through retrieve the historical date of Beijing Jingqiao Power Plant, analyze the action of bypass desuperheating water valve, and the regulating quality. Eventually, find out the two major difficulties:measuring lag and the change of system transfer function. And to analyze and research on these two points, the object of study is no longer stay in the controlled object, but also the control strategy. For getting rid of the limitations of the classic PID control, I use more advanced control strategies, and introduce varying parameter control, feedforward control, Smith predictor. The use of a variety of control means, through the feed forward to improve the speed, variable parameter control in closed loop to improve the accuracy of regulation, the use of Smith predictor to reduce the measuring lag. The quality of the adjustment has been significantly improved, and the adjustment process is more gentle, operation of the unit is more stable, the impact of the pipe material is also more ease.Finally, the research results are applied to the control of real units. The control parameters are further optimized in the conditions of starting stopping and trip. Bypass desuperheating water control strategy optimization tasks is successfully completed. Further, I provide a simple feedforward control solution and variable parameter control solution for general plant maintenance personnel. The research results in this paper can easily applied.