Effect of low voltage ride through (LVRT) characteristic on voltage stability

The number of wind installations has grown worldwide at unprecedented rates in recent years. As well, the average size of the installations has increased due to the advent of larger capacity machine, variable speed technology, and an increasing number of off-shore sites. This raises the concern that widespread tripping of wind generators following disturbances could lead to propagation of transient instabilities and could potentially cause local or system wide blackouts. This has provoked many utilities to adopt low voltage ride-through (LVRT) for wind turbines. The requirement places an added interconnection cost on the manufacturer and will influence the overall financing of the project. This paper presents the LVRT characteristic, reviews the effect that voltage dips have on the operation of the different wind generator topologies and considers the technical requirements for its realization. System studies demonstrate its benefits while establishing a relationship between the shape of the characteristic and the strength of the interconnection. Results suggest that for stronger systems the profile may be excessive whereas for weak interconnections the demands placed upon the manufacturer are likely warranted.