Direct computation of variable speed pumps for water distribution system analysis

The paper introduces the Variable Speed Pump coefficient direct computation that has been implemented in the latest water distribution modelling software. The water distribution simulation packages are often based upon EPANET hydraulic solver that has been developed by employing the Global Gradient Algorithm (GGA). Originally, the computation of the Variable Speed Pumps (VSP) coefficient was an iterative procedure, which could lead to convergence problem. In order to overcome this problem, a direct com-putation algorithm of the VSP coefficient was incorporated into the GGA, giving rise to a complex non-symmetric problem, which was solved by partitioning the original system matrix to lead to the solution of a large symmetrical problem, which size remains more or less the number of demand driven nodes, plus a small non-symmetrical problem, which size equals the number of VSPs. The results of the approach were tested on the benchmark examples. After exhaustive debugging and testing, the algorithm was finally introduced in WaterCAD and WaterGEMS for the purposes of water distribution system analysis

Automatic Parameter Estimation Extension for Variable Speed Pumps

A method for estimating the relative speed factor parameter for a variable speed pump in a hydraulic network sufficient to maintain a fixed pressure at a control node is provided. A desired operating characteristic is determined and this is inserted into a matrix of equations describing the hydraulic system. The largely symmetrical matrix includes certain aspects of the system representing the variable speed pumps which are non-symmetrical. Non-symmetrical portions of the matrix are separated out and solved using an LU factorization technique. Non-sparse, non symmetric matrices are generated and the difference in head correction is solved for to compute the updated nodal head vector and ultimately determine the variable pump speed parameter. The invention allows estimation of the variable speed factor for a variable speed pump drive sufficient to maintain a fixed pressure at a control node. The system fully integrates variable pump speed operation with the status and control capabilities of known hydraulic network solvers