In 1973 [11] the IEESGO model was introduced, which is also a legacy model, and only slightly more detailed than the TGOV1 model. It is shown below in Figure 2‐2. In this case droop is effected by the gain K1 (equivalent to 1/R in the TGOV1 model) and two turbine fractions are introduced (K2 and K3) to represent different stages in the steam turbine. 2