Emerson Process Management Power & Water Solutions, Inc.

Richard J Whalen, Jr

Robert Allen Beveridge

Xu Cheng

Ranjit Ramesh Rao

A control system for controlling a steam turbine power plant having multiple steam flow paths that converge to a combined steam path controls the final steam temperature of the steam input into the turbine by controlling one or more temperature control devices in each of the steam flow paths. The control system includes a multivariable controller, such as a multi-input/multi-output (MIMO) controller, that produces two control signals that control each of a set of downstream control valves in the split steam flow paths. The controller receives two inputs in the form of measured or calculated process variables including the final steam temperature and the inter-stage temperature difference between the steam being produced in each of the two split steam paths and performs multi-objective control based on these inputs. However, when one of the downstream control valves is placed into a manual mode, the controller shifts to being a single objective controller to control the final steam temperature of the system and to thereby perform better or more optimal control.

Multi-objective steam temperature control

A technique of controlling a steam generating boiler system includes dynamically tuning a rate of change of a disturbance variable (DV) to control operation of a portion of the boiler system, and in particular, to control a temperature of output steam to a turbine. The rate of change of the DV is dynamically tuned based on a magnitude of an error or difference between an actual and a desired level of an output parameter, e.g., output steam temperature. In an embodiment, as the magnitude of the error increases, the rate of change of the DV is increased according to a function f(x). A dynamic matrix control block uses the dynamically-tuned rate of change of the DV, a current output parameter level, and an output parameter setpoint as inputs to generate a control signal to control a field device that, at least in part, affects the output parameter level.

Dynamic tuning of dynamic matrix control of steam temperature

A technique of controlling a steam generating boiler system includes using a rate of change of disturbance variables to control operation of a portion of the boiler system, and in particular, to control a temperature of output steam to a turbine. The technique uses a primary dynamic matrix control (DMC) block to control a field device that, at least in part, affects the output steam temperature. The primary DMC block uses the rate of change of a disturbance variable, a current output steam temperature, and an output steam temperature setpoint as inputs to generate a control signal. A derivative DMC block may be included to provide a boost signal based on the rate of change of the disturbance variable and/or other desired weighting. The boost signal is combined the control output of the primary DMC block to more quickly control the output steam temperature towards its desired level.

Steam temperature control using dynamic matrix control

A technique of controlling a steam generating boiler system using dynamic matrix control includes preventing saturated steam from entering a superheater section. A dynamic matrix control block uses a rate of change of a disturbance variable, a current output steam temperature, and an output steam setpoint as inputs to generate a control signal. A prevention block modifies the control signal based on a saturated steam temperature and an intermediate steam temperature. In some embodiments, the control signal is modified based on a threshold and/or an adjustable function g(x). The modified control signal is used to control a field device that, at least in part, affects the intermediate steam and output steam of the boiler system. In some embodiments, the prevention block is included in the dynamic matrix control block.

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Pittsburgh, PA, United States of America

Richard J Whalen, Jr