Accurate, stable and highly responsive gas turbine startup speed control with fixed time acceleration especially useful in combined cycle electric power plants

摘要

A combined cycle electric power plant includes gas and steam turbines and steam generators and a digital/analog control system. An automatic digital portion of the control system includes a speed control which generates a speed error from the actual turbine speed and a turbine speed reference, and a proportional plus integral controller acts on the speed error to generate a fuel reference for the gas turbine fuel valve position controls after ignition and during wide range speed control. A speed reference generator includes a stored representation of speed as a function of time with zero time made equal to the point in time at which the flame goes on. The speed versus time characterization is made up of three linear parts having different slopes. Fixed time acceleration is achieved by causing the speed reference to increase to the synchronous value in accordance with the characterization over the fixed time period and by operating the turbine with the speed control so that the actual turbine speed quickly and accurately follows the speed reference. If a speed hold or speed runback occurs during startup acceleration, the speed reference characterization can be adjusted to provide partial or full makeup of time lost during the hold or runback.