Controlling Strategies for Meshed Offshore DC Collector Grids

The grid integration of future wind farms far away from the shore demands efficient energy transmission systems. Moreover, the growth of generator power leads to the need of transmission lines and grids with huge power transmission capacities. To establish reliable offshore grids with low losses, HVDC systems are proposed as a suitable solution. The direct coupling of wind turbine generator systems (WTGS) to a DC collector grid is considered to avoid offshore AC collector grids with large reactive losses. Meshes in the grid lead to the possibility of linking different offshore transmission lines on the one hand and, on the other hand, a meshed grid is more robust against disturbances within the grid or on single transmission lines. This paper presents centralised and decentralised methods to control a meshed DC collector grid and compares advantages and disadvantages by simulation.