Dynamics and control of multi-terminal high voltage direct current networks for integration of large offshore wind parks into AC grids

Abstract

The integration of larger and larger amounts of wind power is a major target of the European Union, however it represents a challenge for power system planning and operation. The present paper analyses stability aspects concerning the operation of MTDC networks connecting offshore wind farms to the AC systems. Modelling issues are tackled, relevant to control schemes needed for a secure operation of the overall AC-DC system in case of contingencies both on the AC side and on the DC side. First, a power flow control strategy is proposed for the 'backbone' HVDC grid topology (consisting of point-to-point connections between offshore wind farms and mainland grid, crossed by cross-cutting connections). Secondly, dynamic models for the basic control schemes for converters (suitable to investigate electromechanical transients) are illustrated and some stability issues connected to the network performance under contingencies/disturbances is pointed out.