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.