Impact of Microgrids on Power Factor measurements

The penetration of Distributed Energy Resources (DERs) on the power system has come with its own set of problems, especially in the power quality (PQ) domain. Such penetration has led to the re-evaluation of various aspects of distribution PQ. While such a re-evaluation has focused on the emission and compatibility limits, in the light of PQ concerns from inverter interfaced generation, traditional PQ indices themselves have received relatively little attention. This paper highlights one such issue with the measurement of power factor (p.f.). A case study has been presented with measurement data from a residential neighborhood in the United States, which has the capability to island from the grid and operate as a microgrid. The power factor in this case shows significant deviations at various times during the day and night. Upon further investigation, the cause was determined to be PV generation during the day and battery cycling during the night. This paper presents the data from field measurements, the ensuing investigation and the broad conclusions. The paper closes with a discussion of implications of these measurements for utilities and the PQ community, especially with regards to the need for a definition of p.f, that more accurately describes impact of DERs on the grid, given that such situations may recur in the future as DERs and microgrids continue to proliferate.