Design of an Optimum State Regulator for a Once-Through Boiler

Abstract

An optimum state regulator for a once-through boiler is presented in this paper. The ordinary state regulator problem, i.e., bringing the control system from a given initial state to the origin, had to be modified for steam boiler control. The problem arising here is to maintain a desired state, i.e., steam temperature and pressure, in the presence of disturbances, where the load demand is usually regarded as the most important disturbance. In the variable pressure operation, the regulator problem can be formulated as a tracking problem. The turbine output has to follow a given power demand signal as closely as possible. Since in variable pressure operation the turbine output can be assumed to be directly proportional to the steam pressure, the pressure has to follow this signal as well. At the same time the steam temperatures should be maintained at a constant value. This paper is concerned with the variable pressure constant temperature operation. An optimal tracking system including an observer, is designed and compared with the performance of the optimally adjusted actual PID-control equipment.