Superheated Steam Temperature Control Based on Valve Nonlinear Compensation

To ensure the safe and stable operation, it is necessary for a boiler-turbine unit to maintain the superheated steam temperature working in its normal range. When the overheated steam temperature is controlled by adjusting the desuperheating water, the valve nonlinear characteristics, caused by the flow characteristics of water jet reducing valve, will lead to a decline of control quality, if the control scheme is designed without considering it. In this paper, by using Matlab 2013a to build a simulation model, the superheated steam temperature control with valve nonlinear compensation was studied. By collecting the valve input and output data and fitting the valve flow characteristic curve, a valve opening degree compensator based on the polynomial fitting method was designed. Simulation results show that this method can overcome the non-linearity caused by the flow characteristics of the valve to a certain extent so that the control quality of the whole system approaches the linear valve system.