Method for operating a gas and steam turbine installation for frequency support

Abstract

A method for operating a gas and steam turbine system having a gas turbine, a steam turbine and a waste heat steam generator is provided herein, wherein steam for the steam turbine can be generated in the exchange of heat with exhaust gas from the gas turbine. Absorption capacity of the steam turbine can be increased and pressure in the waste heat steam generator can be lowered to utilize storage reserves in the waste heat steam generator for increased generation of steam to assist the frequency in the power system starting from a steady-state operating mode. Thermal energy is fed to the waste heat steam generator wherein a power profile of the gas and steam turbine system is greater than or equal to a preceding power level of the steady-state operating mode to increase the absorption capacity of the steam turbine and reduce pressure in the waste heat steam generator.

1 . A method for operating a gas and steam turbine installation, having a gas turbine, a steam turbine and a waste heat steam generator, in which steam for the steam turbine can be generated by heat exchange with exhaust gas from the gas turbine,
 wherein the method comprises, for frequency support in the power grid, starting from steady-state operation,   increasing the absorption capacity of the steam turbine and decreasing the pressure in the waste heat steam generator in order to use storage reserves in the waste heat steam generator for increased steam generation, and   supplying heat energy to the waste heat steam generator at such a rate that, as a consequence of increasing the absorption capacity of the steam turbine and decreasing the pressure in the waste heat steam generator, a power profile of the gas and steam turbine installation is greater than or equal to an immediately previously available power of the steady-state operation.   
     
     
         2 . The method as claimed in  claim 1 , wherein, in order to increase the absorption capacity of the steam turbine, at least one valve in a bypass duct is opened in order to bypass a steam turbine stage or a steam turbine module. 
     
     
         3 . The method as claimed in  claim 2 , wherein steam is fed via the bypass duct into the steam turbine downstream of a high-pressure intake. 
     
     
         4 . The method as claimed in  claim 2 , wherein steam is fed via the bypass duct into the steam turbine downstream of an intermediate- pressure intake. 
     
     
         5 . The method as claimed in  claim 1 , wherein, in order to increase the absorption capacity of the steam turbine, at least one valve of a control wheel on a high-pressure turbine and/or an intermediate-pressure turbine is opened. 
     
     
         6 . The method as claimed in  claim 1 , wherein the heat energy is supplied by means of increased power from the gas turbine and thus an increased flow of exhaust gas. 
     
     
         7 . The method as claimed in  claim 1 , wherein the heat energy is supplied by an auxiliary firing means. 
     
     
         8 . The method as claimed in  claim 1 , wherein, during steady-state operation, a steam drum pressure is accumulated by means of a valve which is opened for frequency support.