System and method for controlling liquid level in a vessel

A level control system for controlling a liquid level in a vessel having a two-phase medium, the system comprising:

• sensors configured to measure parameters related to the vessel, wherein the parameters comprise liquid level in the vessel, gas flow rate from the vessel, pressure in the vessel, temperature of the vessel, and feed-liquid flow rate into the vessel;
• a controller comprising:
• a signal processing unit configured to receive output signals from the sensors and generate a first filtered output signal representative of liquid level in the vessel, a second filtered output signal representative of gas flow rate from the vessel, a third filtered output signal representative of feed-liquid flow rate into the vessel, a fourth filtered output signal representative of pressure in the vessel;
• and a fifth filtered output signal representative of temperature of the vessel;
• a flow demand control unit configured to receive the first filtered output signal and generate an output signal representative of feed-liquid flow demand;
• a shaping unit configured to receive the second, fourth, and fifth filtered output signals and configured to generate an output signal representative of shaped gas flow rate as function of pressure, temperature, or combination thereof in the vessel;
• and
• a liquid level control unit configured to control the liquid level in the vessel within predetermined limits by controlling one or more components coupled to the vessel based on the output signals from the flow demand control unit, the shaping unit, and the third filtered output signal.

A level control system for controlling a water level in a boiler drum having a two-phase medium;

• the system comprising:
• sensors configured to measure parameters related to the boiler drum, wherein the parameters comprise water level in the boiler drum;
• steam flow rate from the boiler drum;
• pressure in the boiler drum, temperature of the boiler drum, and feed-water flow rate into the boiler drum;
• a controller comprising:
• a signal processing unit configured to receive output signals from the sensors and generate a first filtered output signal representative of water level in the boiler drum, a second filtered output signal representative of steam flow rate from the boiler drum, a third filtered output signal representative of feed-water flow rate into the boiler drum, a fourth filtered output signal representative of pressure in the boiler drum, and a fifth filtered output signal representative of temperature of the boiler drum;
• a flow demand control unit configured to receive the first filtered output signal and generate an output signal representative of feed-water flow demand;
• a shaping unit configured to receive the second, fourth, and fifth filtered output signals and generate an output signal representative of shaped steam flow rate as function of pressure, temperature, or combination thereof in the boiler drum;
• and
• a liquid level control unit configured to control the water level in the boiler drum within predetermined limits by controlling one or more components coupled to the boiler drum based on the output signals from the flow demand control unit, the shaping unit, and the third filtered output signal.