Novel fuzzy logic based coordinated control for multi-unit small modular reactor

Multi-unit small modular reactor (M-SMR) is a nuclear power plant with multiple nuclear steam supply systems (NSSSs) connected to a single shared secondary loop system. Unlike single SMR, strong coupling characteristics of M-SMR will affect safe, smooth and steady operation under both fault and unbalanced load conditions. In order to improve fault-tolerant operation performance, an effective coordinated control strategy (CCS) is required. In this paper, a novel fuzzy logic based CCS with a M-SMR coordinating controller has been proposed, which utilizes two sets of local controllers for each subsystem. In order to meet the operation goal, the coordinating controller generates coordinated control actions using the fuzzy logic approach to coordinate the local controllers and to perform specific control actions. In this paper, we designed two different local controllers to ensure an excellent performance. The first is a back-propagation neural network (BPNN) based PID controller with capability for floating control and the second is a fuzzy controller with capability for quick regulatory control. The control strategy is designed to ensure operation safety of the reactors and to guarantee consistent and stable steam output of the secondary side under fault and unbalanced load conditions. To evaluate the fuzzy logic based CCS, we simulate faults in the 1# NSSS main coolant pumps (MCPs) which create considerable instability to the coordinated control. Simulation results show smoother and steadier operation performance, compared to the BPNN-based PID control strategy.