Centrifugal compressors used for gas compression are complex fluid-flow machines with a limited operational range and control of the compressors is crucial for safe and efficient operation. A model has been created for simulation of a separation and gas compression system on the NEXUS FPSO by using HYSYS DynamicsTM. Based on the theory for centrifugal compressors and control theory a control strategy has been applied to the model based on the available equipment. The model has been used to investigate how the gas compression system responds to changes in the compressor inlet flows and conditions. The simulations performed have resulted in suggestions to modifications to the system.