Study of dynamic response characteristics of S-CO₂ cycle in coal-fired power plants based on real-time micro-grid load and a novel synergistic control method with variable working conditions

In this paper, an integrated dynamic model and the dynamic response characteristics of the S-CO₂ cycle are studied. Furthermore, combined with a micro-grid real-time load with typical fluctuation, a novel synergistic control method for the S-CO₂ cycle under variable dynamic working conditions is proposed. It can lay the foundation of appropriate peak load regulation of a power plant. First, the off-design condition models of the turbo-machineries within the S-CO₂ cycle are constructed. The delay in the changes of thermodynamic parameters of recuperators is considered because of the thermal inertia under dynamic conditions. Second, the dynamic response models of the S-CO₂ cycle are further developed. When the key thermodynamic parameters are step changed, the dynamic response characteristics of S-CO₂ cycles are explored. Third, the variation of the power and efficiency of different S-CO₂ cycles under the variable working conditions with the stability constraint of the power generation frequency is compared. Finally, the S-CO₂ cycle is applied to a micro-grid whose real-time load has typical peak and valley characteristics. The dynamic response characteristics of the power generation frequency and efficiency under the action of two control methods are compared. A novel synergistic control method is further proposed by combining the advantages of both with the constraint of 50 Hz. The result presents that the integral average efficiencies of the S-CO₂ cycle via temperature major control method and mass flow rate major control method are 37.42% and 34.57%, respectively. The power generation frequency fluctuates are within 4% and 2%, respectively. With the novel synergistic control method, the integral average efficiency of the system is 36.88%. The power generation frequency fluctuates are within 2%. There is a balance between power generation stability and power generation efficiency.