The power grid's demand for performance of thermal power units' primary frequency regulation becomes more and more strict. However

in all the double-reheat units which has been put into service in China

poor performance of primary frequency regulation has been observed. On the basis of the IEEE classical models

a new primary frequency modulation model for double-reheat units was established

the genetic algorithm was applied to identify the model parameters and the test data were employed to analyze the primary frequency regulation performance of the double-reheat units. Comparison between the identified model simulation and the test record verifies the effectiveness of the proposed model. The results show that the inherent characteristics of the ultra-supercritical double-reheat unit limit their primary frequency regulation performance greatly

which is hard to improve only by control logic optimization.