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Unit Coordinated Control for Supercritical Boilers
The Ovation® expert control system offers Unit
Coordinated Control (UCC) that provides a
coordinated front-end control strategy that unites
the boiler and turbine controls. Coordinated
controls generate and regulate the setpoint for
unit load (MW). The unit load setpoint or UCC
MW Demand may be generated from local
operator entry, remote increase/decrease
contact inputs, or internally generated
contingencies such as runbacks and rundowns.
Unit coordinated control manages unit load
(megawatts) and throttle pressure by sending
out parallel demand signals to the boiler and
turbine control loops through the Boiler Master
and Turbine Master M/A Stations, respectively.
The Boiler Master demand is used as a feedforward
signal to the feedwater master
(controlling feedwater flow) and to the firing rate
master (controlling fuel and air flow) to improve
unit response to load changes. There is a ratio
function only between the Boiler Master and
firing rate master. The feedwater/firing rate ratio
station controls the long term final temperature
by using the ratio function between the boiler
and firing rate masters. The ratio function
changes the relationship between the feedwater
flow and firing rate, resulting in a change in final
temperature. The spray valves control the short
term final temperature.
The Turbine Master demand controls the turbine
control valves by sending an analog output
signal to the turbine controls.
The operator interface to unit control is through
a dedicated graphic and associated pop-up
windows which may be accessed at an
Operator’s station.
Features
- Provides a coordinated front-end control strategy that unites boiler and turbine controls
- Startup control including the transition from wet to dry mode
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Seamless control throughout all regions from subcritical to supercritical operation
- Sliding pressure for efficient operation at lower loads
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