Thesis - Control of Offshore Wind Power Plant with HVDC grid connection

More wind farms are located further offshore, and thus conventional AC transmission is either not an economic or technological option. At the same time, wind farms are increasingly required to comply with the grid codes and act as a conventional power plant.

This thesis is to investigate the controllability of a wind power plant connected through an HVDC link.

Starting from a point-to-point connection, a model of an offshore wind power plant connected through a HVDC link to an onshore AC system will be developed. The system operation based on this model will be analyzed.

The modeling includes various subsystems, i.e. model of the wind power plant and associated controller, implementation of a wind regime, model of AC power system and the HVDC interconnection with corresponding converter controller. Apart from modeling, this will include exploration of different control functionalities.

The modeling and simulation will be carried out by means of a simplified Matlab Simulink model, and the attained results are to be compared with a more thorough, existing model of the same system in DIgSILENT PowerFactory. In the comparison of the two models, the Matlab Simulink results with respect to HVDC voltage control and primary frequency control regarding the AC grid are of interest. Further functionalities may be investigated in this configuration once the performance of the model has been considered acceptable.

Moreover when the point-to-point model is considered to provide credible results, the Matlab Simulink model is to be expanded; representing a multiterminal HVDC grid network, which interconnects two asynchronous power systems and a wind power plant. By means of this model, HVDC voltage control and frequency control with respect to the two linking AC systems will be investigated.