Gas turbine load/unload path control

A method for operating a gas turbine (GT) system, the gas turbine (GT) system including a compressor feeding air to a combustion section that is coupled to a turbine, the combustion section including a plurality of combustors, at least one of the plurality of combustors including a primary combustion stage including a first plurality of fuel nozzles and a secondary combustion stage downstream from the primary combustion stage, the secondary combustion stage including a second plurality of fuel nozzles, the at least one of the plurality of combustors having a primary combustion stage exit temperature of a combustion gas flow between the primary combustion stage and the secondary combustion stage, the method comprising:

• progressing through each of a plurality of progressive combustion modes, each of the plurality of progressive combustion modes defining a respective predefined target range for the primary combustion stage exit temperature;
• controlling the primary combustion stage exit temperature of the combustion gas flow to be within the respective predefined target range during the progressing through each of the plurality of progressive combustion modes;
• wherein the plurality of progressive combustion modes include at least a fifth mode, a sixth mode, and a seventh mode, wherein only a portion of the first plurality of fuel nozzles are activated and none of the second plurality of fuel nozzles are activated in the fifth mode, wherein all of the first plurality of fuel nozzles are activated and none of the second plurality of fuel nozzles are activated in the sixth mode, and wherein all of the first plurality of fuel nozzles are activated and only a portion of the second plurality of fuel nozzles are activated in the seventh mode;
• and
• wherein the progressing further includes:
• unloading the gas turbine (GT) system by sequentially progressing from the seventh mode, to the sixth mode, to the fifth mode, and
• loading the gas turbine (GT) system by sequentially progressing from the fifth mode, to the sixth mode, to the seventh mode, and wherein during the loading while progressing to the seventh mode from the sixth mode, modifying a split of fuel flow between the primary combustion stage and the secondary combustion stage by decreasing a fuel flow to the first plurality of fuel nozzles and increasing a fuel flow to the second plurality of fuel nozzles thereby maintaining the primary combustion stage exit temperature of the combustion gas flow within the respective predefined target range of the seventh mode.