Steam cooling control for a combined cycle power plant

摘要

A component cooling steam flow control scheme for a combined cycle power plant (12). Steam pressure in the steam drum (40) of a waste heat recovery steam generator (36) is controlled by selectively positioning a steam bypass valve (54). The flow of steam from the steam drum through a cooling steam flow path (46) is controlled by selectively positioning a steam admission valve (50) in the cooling steam flow path. At power levels below a predetermined crossover power level (72), the cooling steam flow is controlled independently from the steam drum pressure, thus assuring good system controllability at the lower power levels where system control is historically a concern. The steam admission valve is maintained fully open at power levels above the crossover power level, so changes in cooling steam flow at these higher power levels are accomplished by regulating steam drum pressure. System efficiency losses resulting from pressure drop across the steam admission valve are thus minimized at the higher power levels where system efficiency is historically a concern.