Patent Number: 
Section: claims

1. A system for controlling a main feed-water pump and a main feed-water control valve including a downcomer feed-water valve and an economizer feed-water valve to control a steam generator level of a nuclear power plant, comprising:a proportional-integral (PI) controller which performs a PI operation on a compensated steam generator error signal generated according to a deviation between the steam generator level and level setpoints of the steam generator and generates a flow demand signal according to the result of the PI operation;a power determiner which determines a power section to which reactor power belongs, among low and high power sections and determines a transfer time when the determined power section transfers;a main feed-water controller which generates a main feed-water control signal for controlling the main feed-water pump and the main feed-water control valve according to the flow demand signal and the determined power section;an information provider which provides PI information comprising a gain and an integral time constant set according to the reactor power; andan information transformer which provides the PI information to the PI controller and provides transformed PI information comprising a transformed gain and a transformed integral time constant to the PI controller only for a predetermined timer time at the transfer time,wherein the transformed gain and the transformed integral time constant are preset to vary with the timer time. 2. The system of claim 1, wherein the information transformer comprises:a transformation information provider which provides the transformed gain and the transformed integral time constant to the PI controller; anda first timer which provides the PI information to the PI controller and provides the transformed PI information to the PI controller only for a predetermined first timer time at a first transfer time when the transfer time transfers from the low power section to the high power section. 3. The system of claim 2, wherein the information transformer comprises:a second timer which provides the PI information to the PI controller and provides the transformed PI information to the PI controller only for a predetermined second timer time at a second transfer time when the transfer time transfers from the low power section to the high power section. 4. The system of claim 1, wherein the transformed gain is set to a value greater than a gain set according to the reactor power, and the transformed integral time constant is set to a value smaller than an integral time constant set according to the reactor power.