Protection safety margin and back pressure protection control method used during change of heating steam extraction capacity of 300MW high back pressure unit

The invention relates to a protection safety margin and back pressure protection control method, in particular to a protection safety margin and back pressure protection control method used during change of heating steam extraction capacity of a 300MW high back pressure unit. The method aims to solve the problem that no protection safety margin and back pressure protection control method aiming at the 300MW high back pressure unit exists at present. The method comprises the steps of 1, defining backpressure protection safety margin of the 300MW unit; 2, establishing a DEH backpressure protection fuzzy control rule for the backpressure protection safety margin; 3, controlling the 300MW unit according to the safety margin defined in the step 1 and the control rule established in the step 2. The method can be used for controlling operation of the 300MW unit.