An efficient and well-established technology for power transmission across long distances is high-voltage direct current transmission (HVDC). However, HVDC is currently almost completely limited to peer-to-peer connections or networks with peers situated closely to each other. This contribution introduces the flatness-based design of a feed-forward control of HVDC transmission networks comprising two or more converter stations. The resulting control concept allows for a flexible determination of the power distribution within the network. Furthermore, effects such as power losses and delays due to wave propagation, which are related especially to long transmission lines, can be easily considered. Numerical simulations for an example network are included to prove the value of the results.