Centrifugal compressor active surge controller design based on fuzzy type II

Centrifugal compressors at low mass flow rates are prone to surge instability. In the surge condition, flow rate and discharge pressure collapse suddenly and rise again in rapid succession. These fluctuations cause severe damages to the compressor and its equipment. Surge is a complex and non-linear phenomenon with high uncertainty. In this paper, active surge controller based on fuzzy type II is presented that provides more flexibility in design progress, higher potential for control and modeling the uncertainties. The proposed surge control specifies and monitors the compressor operating point deviation from the surge point. If this surge deviation reduces so this controller reforms capacity control system commands and keeps the compressor flow rate at the admissible minimum value by opening an anti-surge valve. Simulation results show that the fuzzy type II surge controller acts betters than the fuzzy type I and traditional PID feedback controllers against uncertainties and disturbances especially surge line movements. To improve the reliability and acceptability of the controller, a feedback surge controller with surge avoidance method is used as a backup for the active surge controller.