WATER LEVEL CONTROL DEVICE FOR BOILER DRUM

摘要

PROBLEM TO BE SOLVED: To provide a water level control device for a boiler drum with favorable control performance.;SOLUTION: In a water level controller 43, operational amplification is carried out of a deviation between a boiler drum water level set value and a water level detected value from a water level indicator 4, a steam flow value from a steam flowmeter 5 is added to its output, and a water supply flow value from a water supply flowmeter 2 is subtracted to output an operation amount being an opening command value of a water supply control valve 3. Feedforward compensation circuits 44-48 have a compensation function circuit 44 inputted with a steam flow rate from the steam flowmeter 5, and set with a transfer function neutralizing a dynamic characteristic until water level fluctuation of the boiler drum from the steam flow rate. Since the compensation function circuit 44 is set with the transfer function neutralizing the dynamic characteristic until the water level fluctuation from the steam flow rate, the water level fluctuation is suppressed. Since the feedforward compensation circuits are operated only when a rate of change of the steam flow rate is large, and fluctuation of the water level is large by a dead band circuit 45, an operation frequency of an operation amount of the water supply control valve 3 is suppressed when the steam flow rate is stable.;COPYRIGHT: (C)2007,JPO&INPIT