Sliding Control Applied to Subsea Oil and Gas Separation System under Fluid Transient Effects

Liquid level control inside a subsea gas-liquid separator like VASPS, can be a difficult task. Nonlinearities of the dynamical system combined with disturbances on pipelines flow can result on randomness on liquid level behavior. The control approach chosen for the present study was a robust control generally applied to systems where parts of the dynamics are not well known. The Sliding Control despite of its reliability, induces discontinuities in the system that could be harmful to actuator, an ESP pump for VASPS case. Some adaptations were introduced in order to circumvent this problem. An imprecise system model using fluid transient theory was considered and numerically evaluated by method of characteristics. The present paper purposes a controller robust enough to keep the liquid level between specified limits, track a trajectory to be followed by level values along time and, additionally, able to avoid actuator overwork.