Computer Control System for Thermal Power Plant Boiler Startup

With the increase of the share held by thermal power plants in the total electric power system, a sudden big load variation and a rapid start-up and shut-down of a power plant are becoming very important. It is necessary to develop a control system that is able to respond quickly to a load demand change by using a control computer.The paper deals with the development of a computer control system for boiler startup, which is very difficult to control accuratery the boiler outlet fluid temperature, because not only the boiler time constant is very large, but also the time constant and the gain vary very much during the boiler startup. The steps and results are as follows;(1) The characteristics of a boiler outlet fluid temperature during the boiler startup were analyzed, and the control problems were extracted.(2) The adaptive computer control system which predicts the change of the boiler outlet fluid temperature and automatically requlates control parameters according to the change of boiler characteristics.(3) The control characteristics of the systems at various operational conditions of a plant were analyzed by using a hybrid simulator and an actual power plant.As a result, the stable control characteristics over the whole range of the boiler startup process were demonstrated. Even with the temperature rise from 370 to 400°C, which is said to be the most difficult part in controlling the rise of fluid temperature because the boiler water is transformed into vapor, the deviation of temperature was controlled within 5°C.