Advanced Control Technique Of Centrifugal Compressor For Complex Gas Compression Processes.

LecturePg. 25-32Centrifugal compressors are widely used in petrochemical industries and natural gas fields. One of the major control problems associated with these compressors is pressure fluctuation. In recent years, various control methods have been designed and applied in the field to reduce pressure fluctuation and improve the overall operating stability. This paper describes recent advanced complex gas compression control techniques used for centrifugal compressors, and a verification method using a newly developed control system and dynamic simulator. One of the control techniques used for fuel gas compressors that supply fuel gas to gas turbine combined cycle (GTCC) power plants is described in this paper. Two compressors supply the fuel gas to two independent gas turbines through on common header. Each gas turbine is related to each individual compressor, which has to supply fuel gas for the individual gas turbine according to the load by modulating the control valve opening. The compressor also has to stabilize the common header pressure fluctuation by changing the gas turbine loads. For this process, on control technique is proposed with feed forward (FF) control for the load changing of gas turbine and feedback (FB) control for common header pressure stabilization, as well as application of the above technique in a plant operating in the field. With the FF and FB control, if load shedding of one gas turbine occurs and the gas turbine load suddenly goes down, the other gas turbine can continue operating safely. The compressor control performance is verified with a compressor dynamic process simulator during the design and manufacturing stages prior to shipping. In particular, in order to ensure smooth startup at site, the control panels are connected to the process simulator and the above control technique is applied. Confirmation that all individual functions are working properly is made before shipping