Multilink DC transmission systems for supergrid future concepts and wind power integration

Abstract

A possible methodology for the power sharing is based on DC voltage droop control at onshore station converters. The aim is to present an evaluation tool for the droop control parameter description in support of DC power sharing. Main limitation for this method regarding sharing factors definition and overvoltages are going to be revised. A study case using two different onshore stations are going to be used. Both of them are sized with different power ratings and they have different distances from the offshore converters. This benchmark is suitable as starting point for future prospects of DC supergrids. Using the concept of virtual impedances, the droop parameters are limited by the boundaries of the DC voltage limits and line characteristics. For the power sharing point of view, mainly the cable resistances are considered. Simulation results using time domain simulation (EMTDC/PSCAD) will reinforce the methodology. The approach can be considered as a general case from the previous control schemes based on voltage droop. The work extends the purpose to power sharing characteristic and it can be useful when the converters have different sizes or/and there are restrict agreements among all the operators at onshore AC systems