Method of setting a main controlled variable during the operation of a gas-turbine group

A method of adjusting one of turbine power output and turbine speed during operation of a gas-turbine group, the gas-turbine group including a compressor, at least one combustion chamber, at least one turbine and a generator, the method comprising the steps of:

• measuring one of a turbine power output and turbine speed to determine an output parameter value;
• comparing a desired output parameter value with the measured output parameter value to determine a difference value;
• distributing a first and second difference signal each based on a different portion of the difference value respectively to a turbine inlet temperature control cascade and a compressor output pressure control cascade, each cascade having an output parameter controller to receive the difference signal and convert the difference signal for use by a variable controller which acts on a respective variable actuator;
• wherein, the turbine inlet temperature control cascade receives the first difference signal and adjusts a fuel mass flow according to the first difference signal and the compressor output pressure control cascade receives the second difference signal and adjusts the compressor output pressure according to the second difference signal so that each cascade corrects for a portion of the output parameter difference.