Variable speed drives for power factor correction in the water sector

While solar photovoltaic (PV) panels can offset fuel, emissions, and water use at the power plant, high levels of installed rooftop PV capacity can have negative impacts on the stability and efficiency of the local grid because of power factor (PF) degradation. Specifically, electric utilities have noted voltage fluctuations from solar PV that occur more dynamically than legacy, electromechanical voltage regulation solutions like capacitor banks are designed to correct. At the same time, distributed power electronics devices like inverters can provide the type of dynamic voltage support that utilities seek to maintain reliability while juggling load growth and a greening grid. Using data from Pecan Street Inc. Smart Grid Demonstration Project in Austin, Texas and Austin Water Utility (AWU), this research examines the potential for a three-phase, four quadrant variable speed drive (VSD) in the water sector to provide PF correction to a load pocket of 63 homes experiencing varying levels of PV penetration. In the analysis, the VSD is not reserved for voltage support; instead it is predominantly used to drive a 30 kilowatt (kW) centrifugal sewage pump. The simulation determines the degree to which the VSD can restore PF to a threshold of 0.95, slightly below the targeted value for Austin's electric utility. Further, the economic viability of using the VSD as a grid device is explored by comparing the per unit cost of the PF correction it provides to a current utility solution for dynamic voltage regulation.