Systems and methods for providing override control for a feedwater pump recirculation valve
Systems and methods for providing override control for a feedwater pump recirculation valve are provided. According to one embodiment, a system may include a controller and a processor communicatively coupled to the controller. The processor may be configured to receive one or more measurements associated with pump motor power driving feedwater pump flow. The feedwater pump recirculation valve may be configured to maintain a predetermined minimum recirculation flow through the feedwater pump by regulating recirculation pump flow through a recirculation line. The processor may be also configured to calculate, based at least in part on the one or more measurements, the recirculation pump flow, and compare the recirculation pump flow to the predetermined minimum recirculation flow. Based at least in part on the comparing, the processor may selectively provide an override control signal to the feedwater pump recirculation valve to selectively modify the recirculation pump flow.
1. A method for providing override control for a feedwater pump recirculation valve, the method comprising:
receiving a measured recirculation pump flow rate from a differential-pressure flowmeter, wherein the measured recirculation pump flow rate is a recirculation flow rate through the feedwater pump recirculation valve measured by the differential-pressure flowmeter;
providing, by a controller, a control signal to the feedwater pump recirculation valve, wherein the feedwater pump recirculation valve regulates recirculation flow through a feedwater pump based on the measured recirculation pump flow rate to maintain a predetermined minimum recirculation flow rate through the feedwater pump;
receiving one or more measurements of a current and a voltage of a pump motor that drives feedwater pump flow, the current and voltage being indicative of a consumed electrical power, wherein the current is measured by at least one current transformer, the voltage is measured by at least one potential transformer and wherein the at least one current transformer and the at least one potential transformer are connected to a motor control system;
based at least in part on the one or more measurements, identifying an expected recirculation pump flow rate that corresponds to the one or more measurements using a predefined interpolation function;
comparing the expected recirculation pump flow rate with the predetermined minimum recirculation flow rate;
if the expected recirculation pump flow rate is below the predetermined minimum recirculation flow rate, comparing the expected recirculation pump flow rate with the measured recirculation pump flow rate; and
if the measured recirculation pump flow rate is higher than the expected recirculation pump flow rate providing, by the controller, an override control signal to adjust a position of the feedwater pump recirculation valve and increase flow to above the predetermined minimum recirculation flow rate, wherein the override control signal overrides the control signal provided by the differential-pressure flowmeter.
2. The method of claim 1 , wherein the consumed electrical power is detected by a motor control system.
3. The method of claim 1 , wherein the interpolation function comprises the consumed electrical power versus the recirculation flow.
4. The method of claim 1 , wherein the override control signal is provided to a loop controller of the feedwater pump recirculation valve.