Overspeed anticipation and control system for single shaft combined cycle gas and steam turbine unit

摘要

A system and method for anticipating and controlling overspeed in a combined cycle turbine of the type having a gas turbine with a fuel flow control valve and a steam turbine with at least one steam control valve both disposed on a single shaft and having a heat recovery steam generator heated by said gas turbine and connected to supply steam to the steam control valve, the combined cycle turbine having a unified control system and driving a load. Below a preselected shaft speed the gas turbine fuel command signal controls power. Above the preselected shaft speed the steam turbine speed signal also controls power. Anticipation of overspeed under severe transient load changes, such as loss of electrical load, is provided by a power load unbalance system, wherein gas turbine power and steam turbine power responsive signals are summed after proportionately scaled power responsive signals exceed load by a preselected amount, whereby appropriate action is taken to reduce power before significant overspeed can occur.