RMPC strategy for optimal frequency regulation in DFIG-thermal-storage systems with a mechanical transient model consideration

Abstract

The integrated DFIG-Thermal-Storage system demonstrates superior performance in frequency regulation, wind power integration, energy efficiency, and emission reduction compared to conventional approaches. However, the inherent variability of wind speed and unpredictable load disturbances create significant challenges in optimally allocating frequency regulation power among system components. To address these challenges, this study proposes a robust model predictive control (RMPC)-based frequency regulation strategy that simultaneously accounts for both source-side and load-side disturbances. Firstly, a response model is developed for the DFIG-Thermal-Storage system participating in primary frequency regulation. This model considers the mechanical and electromagnetic characteristics of wind turbines, as well as various constraints such as component operation limits and power balance. Next, to address the uncertainty of wind speed and random load disturbances, the RMPC based method is introduced to modify the frequency regulation model. Furthermore, the strong duality theory is utilized to simplify the min–max double-layer robust optimization model into a single-layer form. The discretization of the component response model is improved using the forward difference method, enabling the solution of the strategy. Lastly, the proposed method is evaluated through several examples in MATLAB/Simulink. The results show that the proposed method reduces operational costs by 8.8% while maintaining effective frequency regulation.