Assessment of interactions involving wind farms in large-scale grids

Abstract

Recently, field events involving adverse interactions between grid-connected inverters (GCIs) and existing power system infrastructures have been reported. Differently than conventional synchronous generating units, GCIs have a wider control bandwidth. Consequently, dynamic interactions among such units and the grid may cause oscillations in wide frequency ranges, revealing, thus, the need for detailed EMT-type models. Screening out potentially critical scenarios in EMT-type large-scale grids is non-trivial and, typically, resource demanding. This works outlines a methodology, namely, the DQ-Scanning technique, which aims at efficiently identifying critical scenarios for new interconnections. The technique is based on the extraction of input admittances and impedances for GCIs and grids, as seen from their point-of-connection, in the dq-frame. It is shown how the resulting admittances and impedances can be used to assess the interconnection stability. The effectiveness of the methodology is demonstrated for the interconnection of a new wind farm to a realistic multi-converter large-scale grid and validated by detailed simulations in EMTP.