Evaluation of the voltage change factor kU for DG equipped with synchronous generators

An evaluation of the voltage disturbances caused by the synchronisation to the grid of distributed generation (DG) resources equipped with synchronous generators is presented. The synchronisation procedures and the resulting transients are first discussed. The effect of the synchronisation conditions (frequency, phase, voltage magnitude deviations) on the resulting fast voltage changes is then demonstrated through an extensive set of simulations. The investigation is extended to the effect of other parameters of the grid and the generator. Objective of the analysis is to shed some light on the selection of appropriate values for the voltage change factor k _U, as per IEC 61400-21, which is used in practical situations to evaluate the fast voltage changes due to the connection of DG power stations.