Mitigating Oscillations in Hydraulic Pumping Systems by Using a Supplementary Damping Controller

A feedback control strategy for mitigating pressure oscillations in centrifugal pumping systems is proposed herein. Severe system damage may occur if such oscillations are not adequately damped. According to the experimental data observed, this dominant oscillating mode is operating point-dependent and may become poorly damped under low-speed regime. By using a theoretical control approach, the key parameters that affect the damping of the dominant oscillating mode are investigated. Linear model analysis show that the relative damping of the oscillations depends on the pumping system's average rotational speed and it is almost zero at low-speed operating condition. To cope with such a dangerous condition, a supplementary feedback damping controller is designed. The damping controller actuates via motor-pump variable-speed drive subsystem. The proposed controller modulates the rotational speed setpoint of the centrifugal pump rotor to produce an extra damping torque. Controller design is performed by using frequency domain techniques, and performance thereof is assessed through experimental tests in a laboratory rig pumping system. The results obtained show that by using the proposed control methodology, it is possible to safely operate the pumping at a low-speed regime, thus preventing damage to the equipment.