Analysis of Boiler Models for Primary Frequency Regulation Studies Considering Working Conditions

Abstract

Accurate simulation of primary frequency regulation (PFR) response of thermal power units is important for frequency safety of power systems. Meanwhile, the PFR capability of the units has shown significant differences in different working conditions. At present, the PFR model of thermal power units commonly used in power system simulation neither includes the boiler model nor considers the variation of working conditions, and the simulation results differ significantly from actual responses in large frequency deviation disturbances. This paper first builds a detailed thermal model of a coal-fired unit that includes boiler dynamics. Then, by simplifying the boiler physics or/and control dynamics, three simplified models are obtained. The effectiveness of these models is studied using actual operating and test data. Comparing the simulation results of different models in frequency disturbance, the trend of model accuracy changing with disturbance size and unit load rate is demonstrated. Finally, the conclusion is that the dynamic control of the boiler has a relatively small impact on the PFR response, but the influence of boiler physical dynamics increases with the increase frequency disturbance size, and the boiler model is the key to reflecting the PFR capability variation with working conditions. The conclusion of this paper clearly inditcates the necessity of including boiler models in PFR studies and recommends appropriate model simplification, which is helpful for the selection of thermal power unit models in frequency safety assessment of power system.