Hierarchical fuzzy logic water-level control in advanced boiling water reactors

A hierarchical fuzzy logic controller (FLC) is applied to control the water level in an analytical simulation using a simplified advanced boiling water reactor model. To reduce the control effort of the feed water pump, the linguistic variable, change in pressure, was adopted. Four linguistic variables were used for the FLC design, and the number of control rules became large if the conventional FLC design method was used. Using a hierarchical rule structure reduces the total number of control rules and thus the final decision tables. To reduce the design effort, two methods were separately developed for fine-tuning. One tunes the scaling factors using an optimization method, and the other tunes the control rules using a method similar to a fuzzy model reference control. The simulation results show that the performance of the hierarchical FLC is comparable to that of the proportional-integral controller, but use of the designed controller results in a shorter settling time.