Reactive power compensation with a UPS unit

Abstract

There is a demand for the compensation of reactive power due to its surplus contents and tariff charges in Finland. The goal of this thesis work was to form a conclusion to the viability of such compensation to be performed with the uninterruptible power supply (UPS). Two theoretical approaches were covered by its centralized compensation: offering reactive power capacity to the local distribution system operator as a grid service and by a compensation of the local site’s reactive loads.

The study method was conducted by referring to standards, measuring the UPS efficiencies during different operation points, and by calculating the annual savings and operation costs in the example scenarios. Sensitivity analyses were carried out with different annual hours of utilization and UPS rated load levels.

The UPS efficiency decreases respectively to the increased reserve power capacity and lower load level. However, the end results show that the example scenarios are profitable in all the studied cases. Three out of the four most profitable cases show that the achieved savings are always proportional to the increasement of the reserve power demand. The results do not include investment costs.