LAUSR

Abstract To balance the intermittent renewable energy (IRE) and to realize its deep penetration, it is necessary for nuclear power plants (NPPs) to operate with enough flexibility. This necessity leads to the concerned questions such as which types of nuclear reactors are suitable for flexible operation and how to realize the operational flexibility of NPPs. In this paper, based on literature review and related analysis, it is shown that the modular high temperature gas-cooled reactor (MHTGR) is suitable for balancing IRE because of the advanced features such as robust fuel elements, online fuel handling, low power density and full-power-range temperature negative feedback effect. Due to the low power density, the power rating of a single MHTGR is lower than those large commercial pressurized water reactors (PWRs). To balance IRE by MHTGRs in a scalable manner, it is recommended to develop NPPs with high rated power based on multimodular scheme, i.e. multiple MHTGR-based nuclear steam supply system (NSSS) modules providing superheated steam for a common turbine. Further, to realize the flexible operation of MHTGR for deep IRE penetration, the automatic generation control (AGC) of multimodular MHTGR plants should be developed. In this paper, two AGC methods including both the adaptive AGC and extended-state-observer (ESO) based AGC are proposed, where the former one has a simple proportional-integral (PI) structure, and the latter one has an additional feedforward compensating action determined by the ESO. The corresponding control system of multimodular MHTGR plants is also designed, which is composed of the units of NSSS control, multimodular coordination control, turbine speed governor (TSG) and AGC. The AGC methods as well as the plant control system design with AGC function are then applied to two modular MHTGR plant HTR-PM. Numerical simulation results show that the newly-built multimodular control system can well stabilize the grid frequency by properly performing the power-level maneuver and maintenance of NSSS modules, and also show that the ESO-based AGC has a better frequency stabilization performance than the adaptive AGC does.