Control system for controlling surge as a function of pressure oscillations and method

A surge control for a multiple stage compressor which produces a compressed gas comprising:

• a surge control valve having a variable opening which is controlled by an electrical control signal which controls a flow rate of compressed gas flowing through a bypass line between a point of higher pressure and a point of lower pressure in the compressor to control surge;
• a plurality of pressure transducers each coupled to an output of a different stage of the compressor for producing an electrical signal representative of the pressure at the output of the stage;
• a plurality of filters, each filter coupled to a different pressure transducer for passing a selected frequency component representative of pressure fluctuations occurring during surge in the signal produced by the pressure transducer to which the filter is connected to produce a filtered signal containing any of the selected frequency component sensed by the pressure transducer coupled to the filter;
• a controller, coupled to the filters, for producing the control signal as a function of the filtered signals;
• and
• a maximum signal detector, coupled to the filtered signals, for producing an output signal which is the filtered signal having the maximum amplitude of the filtered signals produced by the filters with the output signal being coupled to the controller.

A method of controlling surge in a compressor having a surge control valve which controls a flow rate of compressed gas flowing through a bypass line between a point of higher pressure and a point of lower pressure in the compressor comprising:

• sensing a pressure fluctuation at a point in the compressor having a pressure higher than pressure at an inlet to the compressor to produce an electrical signal representative of the pressure fluctuation;
• filtering the electrical signal to separate and pass a selected frequency component representative of pressure fluctuations occurring during surge to produce an electrical signal containing any of the selected frequency component which has been sensed;
• rectifying the electrical signal containing any of the selected frequency component to produce a rectified signal;
• comparing the rectified signal to a reference signal which is a function of compressor noise occurring at a selected point outside a surge region of the compressor to generate an error signal;
• and
• controlling the valve to vary flow rate as a function of the error signal.

A method of controlling surge in a multiple stage compressor having a surge control valve which controls a flow rate of compressed gas flowing through a bypass line between a point of higher pressure and a point of lower pressure in the compressor comprising:

• sensing a selected frequency component of a plurality of pressure fluctuations respectively located at an outlet of different stages representative of pressure fluctuations occurring during surge to produce electrical signals containing any of the pressure fluctuations which have been sensed at the different stages with the frequency component being between 1-10 Hz.;
• rectifying the electrical signal containing any of the selected frequency component having a largest magnitude to produce a rectified signal;
• comparing the rectified signal to a reference signal which is a function of compressor noise occurring at a selected point outside a surge region of the compressor to generate an error signal;
• and
• controlling the valve to vary the flow rate as a function of the error signal.