Control Options for Load Rejection in a Three-Shaft Closed Cycle Gas Turbine Power Plant

An important issue to be addressed in power plants is the continued operation during load transients, such as load following and load rejection. It is inevitable that with new power plant technology, new control strategies will be required. One such technology investigated for commercial power plants is that of a three-shaft recuperative inter-cooled closed-loop Brayton cycle with a high-temperature gas-cooled nuclear reactor as the heat source and helium as coolant. Because of its unique configuration, the utilization of traditional power plant control strategies is limited. In order to address this, detailed cycle analyses were performed to identify new potential control strategies. The analyses were done using the Flownex thermohydraulic systems CFD simulation software since it is ideally suited for component and system integration. It also enables designers to simulate complex load scenarios and design-suitable controller algorithms. It was therefore possible to investigate control options for one of the most severe load control scenarios, i.e., that of full load rejection due to the loss of the grid power. This paper briefly describes the various control strategies investigated and presents details of the two strategies showing the most promising results with regard to load rejection.