Analysis of different single line and combined control characteristics of supercritical carbon dioxide Brayton cycle reactor system under whole load range

The supercritical carbon dioxide Brayton cycle system is widely used in many scenarios. When the power demand changes, the system is often required to perform variable-condition control. It is important to study the system's transient operation characteristics and control characteristics of different control strategies during the power regulation process for the stable control and safe operation of the Brayton cycle system. Based on the established model of the supercritical carbon dioxide Brayton cycle reactor system, this paper first studies the control range limiting factors and transient control characteristics of inventory control. Then analyzes the parameter response characteristics under different conditions by simulating the load change conditions under different bypass controls, and compares and selects different bypass controls based on key parameters. Finally, the control characteristics of various composite controls in the full power range are studied, and the control effects of various conditions are compared and analyzed. The results indicate that the tank volume, initial pressure, and initial temperature limit the inventory control range, and the effects of the first two are more obvious only in a certain range. For the independent control of inventory control and five bypass controls, the thermal efficiency of inventory control is higher, but the overshoot phenomenon is more obvious. Among the five bypass controls, the performance of compressor bypass control 2 is the best, while the performance of reactor bypass control and turbine bypass control 2 is slightly inferior. Three composite control strategies formed by the combination of bypass control and inventory control can realize the step change and linear change control in the 100% -0-100% load range. However, the load step change will make parameters like compressor outlet pressure and reactor outlet temperature fluctuate, and the fluctuation range can be reduced by using the reactor outlet temperature control. Composite control 2 has the best performance among the three composite controls, reducing the reactor power to 27.57%.