Evaluation of a Control Strategy for Meshed Offshore DC Grids in Floating-point and Fixed-point Arithmetic

Meshed offshore DC grids are proposed to connect multiple wind farms to the mainland and to transmit energy between different onshore grids. In this paper a control approach for such a DC grid is evaluated in simulations and on a test stand. With the control approach it is possible to control the voltage of the DC grid or the transmitted power at the different converter stations in the DC grid. The test stand consists of four converter stations and a transmission line replication. With the transmission line replication, the scenario of an offshore DC transmission grid is emulated on the test stand. The controller is implemented in both floating-point and fixed-point arithmetic in the simulation and on the test stand using the Matlab Fixed-Point Tool and Embedded Coder. The accuracy and the program runtime for the different arithmetic are compared. Additionally, the stability of the control approach when disconnecting and connecting individual sections of the DC grid is evaluated.