Exhaust temperature based threshold for control method and turbine

A gas turbine having a controller for controlling an operating point of the gas turbine, the gas turbine comprising:

• a compressor configured to compress a fluid;
• a combustor connected to the compressor and configured to receive the compressed fluid from the compressor and fuel;
• a turbine having a common shaft with the compressor and configured to rotate when receiving burnt fuel from the combustor;
• and
• a processor configured to control an intake of the compressor and the fuel at the combustor, the processor being configured to,
• determine an exhaust pressure at an exhaust of the turbine,
• receive a compressor pressure discharge of the compressor,
• determine a turbine pressure ratio based on the exhaust pressure and the compressor pressure discharge,
• calculate a primary to lean-lean mode transfer threshold reference curve as a function of the turbine pressure ratio, wherein the primary to lean-lean mode transfer threshold curve includes points at which an operation of the gas turbine is changed between a primary mode and a lean-lean mode, and
• control the gas turbine to change between the primary mode and the lean-lean mode,
• wherein the primary mode is defined as providing more than half of the fuel to primary burners and providing a remaining or no fuel to a secondary burner of the combustor and also igniting the provided fuel in a primary region of the combustor, the primary region being adjacent to a secondary region, and
• wherein the lean-lean mode is defined as providing fuel to both the primary burners and the secondary burner and burning the provided fuel both in the primary region and the secondary region.