Optimized operation of water supply systems containing a mixture of fixed and variable speed pumps

An algorithm is presented which caters for the optimized operation of multi-source, multi-reservoir systems, in which pump flows and powers are more or less constant during the whole control period. This condition can be approximately satisfied in many systems where significant storage somewhat decouples direct pump flows from major consumer demands. By using time of pumping instead of pump flow as a decision variable, the formulation of the optimal operation problem for a complete control period results in a large-scale dynamic linear programming problem for which a global optimum can always be guaranteed. The incorporated discretization scheme based on sensitivity analysis, can overcome the difficulties of the mixture of fixed speed pumps (discrete variables) with variable speed and/or throttle pumps (continuous variables)