Gas turbine load/unload path control

A non-transitory computer readable storage medium including code for a control system of a gas turbine (GT) system, the code configured to control a combustion section including a plurality of combustors for a of the gas turbine (GT) system, at least one of the plurality of combustors including a primary combustion stage, the 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 code performing the following during operating of the gas turbine (GT) system:

• 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 of the combustion gas flow;
• wherein the plurality of progressive combustion modes includes at least a fifth mode, a sixth mode, and a seventh mode;
• wherein only a portion of the first plurality of fuel nozzles is activated in the fifth mode 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 in the sixth mode 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 is activated in the seventh mode;
• and
• controlling the primary combustion stage exit temperature of the combustion gas flow to be within the respective predefined target range corresponding to the respective combustion mode during the progressing through each of the plurality of progressive combustion modes;
• and
• wherein the progressing further includes:
• unloading the gas turbine (GT) system by sequentially progressing from at least the seventh mode to the sixth mode to the fifth mode, and
• loading the gas turbine (GT) system by sequentially progressing from at least 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.