The boiler-model based unit control in once-through boilers

摘要

With different time behavior of the boiler and the turbine causes an energy imbalance between two main control variable megawatts (MW) and throttle pressure to fluctuate, the throttle pressure lag and excessive overshoot in coordinated unit control cannot be avoided. There are two methods to improve process dynamic response. When the fuel is step up (step down) process delays of 3～5minutes occur before steam flow and pressure increase. By analyzing results, a model pressure set point and turbine set point can be developed that corresponds to the order of boiler response. A second method is to use a transport turbine master feedforward model to reduce pressure deviations at initial stage of load change. As a consequence, the coordinated unit control response is stable and the result is very good.