A variable universe fuzzy control method for the HCOTSG feedwater system of small pressurized water reactor

Helical-Coil Once-Through Steam Generator (HCOTSG) is a key energy conversion component in the secondary circuit system of Small Pressurized Water Reactor (SPWR), exhibiting lower heat storage capacity and great difficulty in steam pressure regulation. The traditional fuzzy control method adopts a fixed domain of discourse, which has limited adaptability under load change conditions, and it is difficult to meet the requirements of HCOTSG for high precision control. Therefore, this paper proposes a variable universe fuzzy control (VUFC) method for the HCOTSG feedwater system, with the nonlinear mathematical model of the secondary circuit, the real-time adjustment domain of the scaling factor based on fuzzy rules is used to realize the online adaptive control of HCOTSG feedwater system. Simulation results of the SPWR under step load changes show that the VUFC offers faster response speed, smaller overshoot and stronger robustness than traditional fuzzy control, which mitigates the impacts of steam pressure on secondary circuit equipment and improves the operation safety of SPWR.