Model-based coordinated air-fuel control for a gas turbine

A control system for a gas turbine, including:

• a fuel control actuator;
• a combustion air control actuator;
• a coordinated air-fuel controller that controls operations of the fuel control actuator and the combustion air control actuator, wherein the coordinated air-fuel controller receives a plurality of gas turbine condition input signals and determines, based on the input signals, a first error signal, a second error signal, a third error signal and a fourth error signal, and wherein the coordinated air-fuel controller includes:
• a fuel controller that provides a fuel control output signal to the fuel control actuator to control operations of the fuel control actuator,
• wherein the fuel controller processes the first error signal using a first transfer function to obtain a first loop control signal,
• wherein the fuel controller processes the second error signal using a second transfer function to obtain a second loop control signal, and
• wherein the fuel controller determines a preliminary fuel control signal based on at least one of the first loop control signal and the second loop control signal, and determines the fuel control output signal based on the preliminary fuel control signal;
• a combustion air controller that provides a combustion air control output signal to the combustion air control actuator to control operations of the combustion air control actuator;
• and
• a cross-channel controller in communication with the fuel controller, wherein the cross-channel controller processes the preliminary fuel control signal according to an air versus fuel model, to determine an expected steady-state combustion air control signal;
• wherein the combustion air controller processes the third error signal using a third transfer function to obtain a third loop control signal,
• wherein the combustion air controller processes the fourth error signal using a fourth transfer function to obtain a fourth loop control signal, and
• wherein the combustion air controller determines a preliminary combustion air control signal based on at least one of the third loop control signal and the fourth loop control signal, and determines the combustion air control output signal based on the preliminary combustion air control signal and the expected steady-state combustion air control signal.