Variable Pressure Operating System of Steam Power Plant Optimized by Computer

Abstract

Constant pressure operating systems are generally used for steam power plants nowadays, in which, steam pressure is a main control variable.Variable pressure operating systems are used for a few stations in the present day, but have many advantages comparing with above ones, especially for buffer stations receiving rapid and/or large demand power changes. (13)(14)(15)In the former, the most important condition for optimum control is considered for transient response of pressure variation from set point. (1) (2) In the latter, responsibility for demand power is a main item.By differences of details of power plants, many kinds of variable pressure operating system can be arised, but it will be reasonable to classify them into next two categories by fundamental different characteristics.a)Pure variable pressure operationb)Variable pressure operation utilizing thermal capacity.In (a), fuel, air and feed water are controlled according as demand power and governor valve is held at full opening. In (b), it is controlled also for the purpose of effective utilization of thermal capacity of boiler.Conventional control theory is applicable for syntheses of these systems, but modern control theory is more effective for setting up requested performance indeces.The actual system can be constructed by the appropriate combination of conventional analog controllers, but we recommend to combine an on-line digital computer hierarchically for adaptation to non-linearity of boiler dynamics.