Improving Stability of Electronically Controlled Pressure 1 Reducing Valves

The file attached to this record is the author's final peer reviewed version.9 This paper explains the root cause of instabilities which tend to arise in pressure reducing 10 valves (PRVs) under low flow conditions. It was found that the loss of stability in PRVs is a direct 11 result of an increase in the static valve/network gain as the valve position gets smaller, thus making 12 pressure changes more sensitive to valve position adjustments. If the valve controller is tuned at 13 medium valve openings characteristic of normal operating conditions, the increased gain at low 14 valve openings can cause the control system to be too aggressive in its valve position adjustments 15 leading to oscillations. The manuscript provides a mathematical derivation of the gain equation 16 for a simplified pipe-PRV-pipe model. The obtained gain equation curve is then used to derive the 17 formula for a gain compensator whose purpose is to keep the static gain constant across an entire 18 range of permitted valve openings. A simplified network transient model is then used to recreate a 19 real-life PRV instability event and show the remedial effects of the gain compensator