Method for regulating a brief increase in power of a steam turbine

1. A method for regulating a brief increase in power of a steam turbine that has an upstream fossil-fired once-through steam generator comprising a plurality of economizer, evaporator and superheater heating surfaces which form a flow path and through which a flow medium flows, the method comprising:

increasing the flow of the flow medium through the fossil-fired once-through steam generator in order to achieve the brief increase in power of the steam turbine,

using a desired enthalpy value at the outlet of an evaporator heating surface as a control variable for determining a desired value for the flow of the flow medium through the fossil-fired once-through steam generator, and

reducing the desired enthalpy value in order to achieve the brief increase in power of the steam turbine.

2. The method as claimed in claim 1 , wherein the desired enthalpy value is reduced to a predetermined minimum enthalpy value.

3. The method as claimed in claim 2 , wherein the minimum enthalpy value is dimensioned in such a way that complete evaporation of the flow medium in the evaporator heating surfaces is achieved under all load conditions of the fossil-fired once-through steam generator.

4. The method as claimed in claim 1 , wherein the magnitude and/or duration of the reduction in the desired enthalpy value is determined with reference to the required increase in power.

5. The method as claimed in claim 1 , wherein in order to achieve the brief increase in power of the steam turbine, flow medium taken from the flow path is injected in the region of a superheater heating surface of the fossil-fired once-through steam generator.

6. The method as claimed in claim 1 , wherein the heat supply to the fossil-fired once-through steam generator is increased.