Method and system for controlling variable load rate of thermal power generating unit

The invention belongs to the technical field of thermal power generating unit control, and particularly relates to a thermal power generating unit variable load rate control method and system. A target load deviation value is obtained according to the target load after the speed is subtracted from the target load, and a current main steam pressure deviation value is obtained by subtracting the main steam pressure actual value from the main steam pressure set value; the correction coefficient of the rising load change rate corresponding to the current main steam pressure deviation value is multiplied by the manually-input load change rate to obtain the load change rate of the current unit, and when the target load deviation value is smaller than or equal to a preset low alarm value, the load change rate of the current unit is obtained. The correction coefficient of the load reduction change rate corresponding to the current main steam pressure deviation value is multiplied by the manually input load change rat