Method and device for compensating variations in fuel composition in a gas turbine system

A gas turbine system, comprising:

• a plurality of burner stages operated in parallel in which a plurality of fuel control valves are allocated to the burner stages and a regulator is allocated to the fuel control valves;
• and
• a control device for adjusting a fuel supply in the gas turbine system to keep the fuel supply split between the burner stages at a constant target value to compensate for variations in a fuel composition, comprising:
• an analyzer for analyzing the fuel composition,
• a computing unit for calculating a current Wobbe index of the fuel composition based on the analysis, and
• an updating unit for adjusting the regulator and the fuel control valves based on the calculated current Wobbe index, wherein the gas turbine system comprises:
• a fuel line through which a fuel flows;
• a branching point on the fuel line for branching off a part of the fuel and for introducing the branched off fuel as an analysis sample flow;
• and
• a branch line which feeds the analysis sample flow to the analyzer of the control device,
• wherein a distance between the branching point and the fuel control valves is sufficiently elongated to allow:
• the analyzer to fully analyze the fuel composition of the sample flow,
• the computing unit to fully calculate the current Wobbe index, and
• the updating unit to fully adjust the regulator and the fuel control valves before the fuel reaches the fuel control valves.