A HYBRID FUZZY-PI ADAPTIVE-CONTROL FOR U-TUBE STEAM-GENERATORS

This paper presents an adaptive algorithm using fuzzy logic to control the water level of a U-tube steam generator (UTSG). The algorithm improves the response of a standard proportional-integral (PI) controller to nonminimum-phase perturbations by combining fuzzy-logic and gain-scheduling techniques. The new automatic controller can operate under the full range of operating conditions. The level error signal is modified by two fuzzy-logic circuits and a gain-scheduling table before reaching the PI module. Variations in steam pressure and feedwater temperature, which can induce out-of-phase disturbances to the system, are taken into account by the fuzzy-logic modules. The algorithm has been tested by using a simulation of a Westinghouse Electrical Corporation UTSG.