Variable rate feedforward control based on set point rate of change

A power plant controller, comprising:

• an input to receive a load demand set point signal specifying a load demand set point for each of a series of times;
• a calculation unit that determines a magnitude of a rate of change of the load demand set point associated with a particular period of time prior to a current time;
• a comparison unit that compares the determined magnitude of the rate of change of the load demand set point during the particular period of time to a threshold;
• and
• a control signal generator that generates a control signal with a fast response rate when the determined magnitude of the rate of change of the load demand set point during the particular period of time is below the threshold and that creates a control signal with a slow response rate when the determined magnitude of the rate of change of the load demand set point during the particular period of time is greater than the threshold.

A method of producing a control signal for use in controlling equipment in a plant, comprising:

• obtaining a set of set point signal values for a set point signal specifying the desired operation of the equipment over a particular period of time;
• determining a magnitude of a rate of change of the set point signal during the particular period of time based on the set of set point signal values;
• comparing the determined magnitude of the rate of change of the set point signal during the particular period of time to a threshold;
• creating a control signal for use in controlling the equipment based on the comparison between the determined magnitude of the rate of change of the set point signal during the particular period of time and the threshold, wherein the control signal is created with a first response characteristic when the determined magnitude of the rate of change of the set point signal during the particular period of time is below the threshold and the control signal is created with a second response characteristic when the determined magnitude of the rate of change of the set point signal during the particular period of time is greater than the threshold.

A boiler operated power plant, comprising:

• a turbine;
• a boiler coupled to the turbine that operates to create steam to drive the turbine;
• a control unit communicatively connected to the boiler to control the operation of the boiler, the control unit including;
• a feedback controller that produces a feedback control signal;
• a feedforward controller that produces a feedforward control signal, the feedforward controller including;
• an input that receives a load demand set point signal specifying a load demand set point for each of a series of times of operation of the power plant;
• a calculation unit that determines a magnitude of a rate of change of the load demand set point over a particular period of time prior to a current time;
• a comparison unit that compares the determined magnitude of the rate of change of the load demand set point over the particular period of time to a threshold;
• and
• a feedforward control signal generator that generates the feedfoward control signal to include a first response characteristic when the determined magnitude of the rate of change of the load demand set point over the particular period of time is below the threshold and that creates the feedfoward control signal with a second and different response characteristic when the determined magnitude of the rate of change of the load demand set point over the particular period of time is greater than the threshold;
• and
• a control signal combiner that combines the feedforward control signal and the feedback control signal to create a master control signal for controlling the boiler.