Method for achieving primary frequency modulation under pressure control of steam turbine

The invention relates to a method for achieving primary frequency modulation under the pressure control of a steam turbine. The method for achieving primary frequency modulation under the pressure control of the steam turbine comprises the following steps that firstly, a primary frequency modulation demand load is converted into a pressure setting modification value; secondly, the speed setting parameter of a first speed limiting block is obtained; thirdly, the speed setting parameter of a second speed limiting block is obtained; and fourthly, a first change-over switch signal serves as the speed setting parameter of the first limiting block, a second change-over switch signal serves as the speed setting parameter of the second limiting block, speed limiting is conducted through the first speed limiting block, a pressure setting modification value output by the first speed limiting block and a pressure setting modification value output by the second speed limiting block are superposed, the superposition value is output to serve as the set value of a pressure-control PID module of the steam turbine, the actual main stream pressure serves as the actual value, and a valve control command is output through the calculation of the pressure-control PID module of the steam turbine. By the adoption of the method for achieving primary frequency modulation under the pressure control of the steam turbine, the problem that the primary frequency modulation performance is affected due to the fact that most units operate under the pressure control of the steam turbine is solved, and the primary frequency modulation function can be achieved when the units operate under the pressure control of the steam turbine.