Improving Stability of Electronically Controlled Pressure-Reducing Valves through Gain Compensation
Publication: Journal of Hydraulic Engineering
Volume 144, Issue 8
Abstract
This paper explains the root cause of instabilities that tend to arise in pressure-reducing valves (PRVs) under low-flow conditions. It was found that the loss of stability in PRVs is a direct result of an increase in the static valve-network gain as the valve position gets smaller, thus making pressure changes more sensitive to valve position adjustments. If the valve controller is tuned at medium valve openings characteristic of normal operating conditions, the increased gain at low valve openings can cause the control system to be too aggressive in its valve position adjustments, leading to oscillations. This paper provides a mathematical derivation of the gain equation for a simplified pipe-PRV-pipe model. The obtained gain equation curve was then used to derive the formula for a gain compensator whose purpose is to keep the static gain constant across an entire range of permitted valve openings. A simplified network transient model was then used to recreate a real-life PRV instability event and show the remedial effects of the gain compensator.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The authors wish to thank Alan Woodburn for his valuable comments and providing the data for the case study.
References
Berardi, L., D. Laucelli, R. Ugarelli, and O. Giustolisi. 2015. “Leakage management: Planning remote real time controlled pressure reduction in Oppegård municipality.” Procedia Eng. 119: 72–81. https://doi.org/10.1016/j.proeng.2015.08.855.
Brunone, B., and L. Morelli. 1999. “Automatic control valve: Induced transients in operative pipe system.” J. Hydraul. Eng. 125 (5): 534–542. https://doi.org/10.1061/(ASCE)0733-9429(1999)125:5(534).
Campisano, A., C. Modica, S. Reitano, R. Ugarelli, and S. Bagherian. 2016. “Field-oriented methodology for real-time pressure control to reduce leakage in water distribution networks.” J. Water Resour. Plann. Manage. 142 (12): 04016057. https://doi.org/10.1061/(ASCE)WR.1943-5452.0000697.
Campisano, A., C. Modica, and L. Vetrano. 2012. “Calibration of proportional controllers for the RTC of pressures to reduce leakage in water distribution networks.” J. Water Resour. Plann. Manage. 138 (4): 377–384. https://doi.org/10.1061/(ASCE)WR.1943-5452.0000197.
Creaco, E., A. Campisano, M. Franchini, and C. Modica. 2017. “Unsteady flow modeling of pressure real-time control in water distribution networks.” J. Water Resour. Plann. Manage. 143 (9): 04017056. https://doi.org/10.1061/(ASCE)WR.1943-5452.0000821.
Evans, W. R. 1950. “Control system synthesis by root locus method.” Trans. Am. Inst. Electr. Eng. 69 (1): 66–69. https://doi.org/10.1109/T-AIEE.1950.5060121.
Ferrante, M., S. Meniconi, and B. Brunone. 2014. “Local and global leak laws: The relationship between pressure and leakage for a single leak and for a district with leaks.” Water Resour. Manage. 28 (11): 3761–3782. https://doi.org/10.1007/s11269-014-0708-x.
Ghorbanian, V., B. W. Karney, and Y. Guo. 2015. “The link between transient surges and minimum pressure criterion in water distribution systems.” In Proc., Pipelines 2015. Reston, VA: ASCE.
Giustolisi, O., A. Campisano, R. Ugarelli, D. Laucelli, and L. Berardi. 2015. “Leakage management: WDNetXL pressure control module.” Procedia Eng. 119: 82–90. https://doi.org/10.1016/j.proeng.2015.08.856.
Hazewinkel, M., ed. 1994. Encyclopaedia of mathematics. 1st ed. Dordrecht, Netherlands: Springer.
Hubbard, J. H., and B. B. Hubbard. 2015. Vector calculus, linear algebra, and differential forms: A unified approach. Ithaca, NY: Matrix Editions.
Janus, T., and B. Ulanicki. 2017. “Hydraulic modelling for pressure reducing valve controller design addressing disturbance rejection and stability properties.” Procedia Eng. 186: 635–642. https://doi.org/10.1016/j.proeng.2017.03.280.
Jung, B. B. S., P. F. Boulos, and D. J. Wood. 2009. “Effect of pressure-sensitive demand on surge analysis.” Am. Water Works Assoc. J. 101 (4): 100–111. https://doi.org/10.1002/j.1551-8833.2009.tb09877.x.
Meniconi, S., B. Brunone, M. Ferrante, E. Mazzetti, D. Laucelli, and G. Borta. 2015. “Transient effects of self-adjustment of pressure reducing valves.” Procedia Eng. 119 (SC): 1030–1038. https://doi.org/10.1016/j.proeng.2015.08.999.
Meniconi, S., B. Brunone, E. Mazzetti, D. B. Laucelli, and G. Borta. 2016. “Pressure reducing valve characterization for pipe system management.” Procedia Eng. 162: 455–462. https://doi.org/10.1016/j.proeng.2016.11.088.
Meniconi, S., B. Brunone, E. Mazzetti, D. B. Laucelli, and G. Borta. 2017. “Hydraulic characterization and transient response of pressure reducing valves: Laboratory experiments.” J. Hydroinf. 19 (6): 798–810. https://doi.org/10.2166/hydro.2017.158.
Ogata, K. 2010. Modern control engineering. 5th ed. Boston, MA: Pearson.
Page, P. R., A. M. Abu-Mahfouz, and S. Yoyo. 2016. “Real-time adjustment of pressure to demand in water distribution systems: Parameter-less P-controller algorithm.” Procedia Eng. 154: 391–397. https://doi.org/10.1016/j.proeng.2016.07.498.
Prescott, S. L., and B. Ulanicki. 2003. “Dynamic modeling of pressure reducing valves.” J. Hydraul. Eng. 129 (10): 804–812. https://doi.org/10.1061/(ASCE)0733-9429(2003)129:10(804).
Thornton, J., and A. Lambert. 2005. “Progress in practical prediction of pressure: Leakage, pressure: Burst frequency and pressure: Consumption relationships.” In Proc., IWA Special Conf. on Leakage, 12–14. London, UK: International Water Association.
Ulanicki, B., and P. Skworcow. 2014. “Why PRVs tend to oscillate at low flows.” Procedia Eng. 89: 378–385. https://doi.org/10.1016/j.proeng.2014.11.202.
Vicente, D. J., L. Garrote, R. Sánchez, and D. Santillán. 2015. “Pressure management in water distribution systems: Current status, proposals, and future trends.” J. Water Resour. Plann. Manage. 142 (2): 04015061. https://doi.org/10.1061/(ASCE)WR.1943-5452.0000589.
Wylie, E. B., and V. L. Streeter. 1993. Fluid transients in systems. Facsimile edition. Englewood Cliffs, NJ: Prentice Hall.
Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 144 • Issue 8 • August 2018
Copyright
©2018 American Society of Civil Engineers.
History
Received: Apr 16, 2017
Accepted: Mar 5, 2018
Published online: Jun 14, 2018
Published in print: Aug 1, 2018
Discussion open until: Nov 14, 2018
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.