Influence Analysis of Thermal States on Dynamic Frequency Response for Power Systems with High Renewables

As thermal generators are substituted by renewables, the power reserves are decreasing and the influence of boiler thermal states on frequency dynamics becomes more severe. The variations of thermal states can aggravate dynamic frequency response, especially for power systems with high renewables. However, the system frequency response (SFR) model has been widely adopted, but in which the thermal states are neglected. This paper analyzes the influence of thermal states on dynamic frequency response quantitatively. The modified SFR models are built by extending the boiler models with different simplification degrees. Then, from the view of the response amplitude and time, the quantitative indices are established to measure the response trajectories of modified SFR models. And the characteristics of frequency dynamics and the statistic indices of data sequences are utilized to analyze the influences of thermal states and assess the performances of modified SFR models. According to the results of comparative analysis, the neglect of thermal states incurs more optimistic frequency dynamics and impairs the frequency stability of power systems with high renewables. Additionally, the accuracy of the SFR model can be enhanced even with the most simplified boiler model.