A fuzzy controller based on self-tuning rules for the nuclear steam generator water level.pdf
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K S M E International Journal, Vol. 11, No. 5, pp. 485~ 493, 1997
A Fuzzy Controller Based on Self-Tuning Rules
for the Nuclear Steam Generator Water Level
485
Man Gyun Na* and Jae Hyung Lim**
(Received December 5, 199.5)
It was demonstrated that the fuzzy control method could be applied successfull~ to control
and regulate the nuclear steam generator water level through previous works. However, this
method has some limitations from the fact that its performance largely depends on the tuning
method and how to settle the rule base. In this work, a fuzzy control algorilhm based on self
--tuning rules is investigated to find the optimal tuning point and to generate the control rule
automatically. It adopts an on-l ine iterative method and the objective error function which
contains the variation errors of all time-steps. The triangular membership functions based on the
mass flow rate and water level errors are applied. And also, a torgetting factor is used to account
for an exponential decay of the past data in tracking the slow drift in system paramelers. Thus
it controls the steam generator water level flom low power to lull power with a little transients.
This control algorithm is validated by computer simulations.
Key Words: Fuzzy Control, Membership Function, Self-Tuning Rule
I. In troduct ion
The proper control of the water level of a
nuclear steam generator is of much importance in
order to secure the sufficient cooling source of the
nuclear reactor and the good performance of the
steam separator and dryer, and to prevent the
damage of turbine blades. The steam generator
level control has been a main culprit of un-
expecled shutdown of nuclear power plants. The
non rainimum phase effects are significantly
greater at low power, which makes more perilous
the use of a high gain of the control loop at the
reduced power level.
Main objective of this work is to design a
controller that not only makes the feed water mass
flow rate tra
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