A system and method for operating a gas turbine in a turndown mode

A system for operating a thermal power plant 10 during off-peak demand intervals includes a gas turbine 12 having a compressor 18, a combustor 22 connected to a fuel control system 26, a turbine 30 and a sensor 62 configured to sense ambient conditions around the gas turbine 12. The fuel control system 26 and the sensor 62 are in communication with a controller 60. The controller 60 is configured to receive a user input that corresponds to a value for an operational boundary condition of the thermal power plant 10 and to monitor ambient conditions through the sensor 62. The controller 60 is further configured to generate a predicted emissions level value for the gas turbine 12 based on the monitored ambient conditions and to generate a command signal to adjust at least one operational parameter of the gas turbine 12 based at least in part on the predicted emissions level value and the value of the operational boundary condition of the thermal power plant 10.