Power flow analysis of meshed AC-DC super grid

The unbundling of power market and continuous increase of renewable generation over the years has resulted in bulk power transmission over long distances and cross-border links. Moreover, Integration of renewable generation is set to increase every year to fulfil EU´s vision and other country specific goals. These require an expansion of existing conventional AC transmission network to hybrid/meshed AC-DC. In this regard, several point to point projects all around Europe have been planned, some of which are already up and running. Next step towards this is the building of multi-terminal HVDC grids. The construction of multi-terminal DC (MTDC) leads to major changes in the power flow of the existing grids. This paper investigates such meshed AC-DC grids and attempts to predict the behaviour of the future grids via load flow studies. To facilitate the power flow and easier flow control, a new type of interface node for the converter nodes has been proposed which has been tested on a small test system. Finally, power flow analysis has been done on a simplified model of North-Western European grid connected to Great Britain grid and Nordic grid via DC interconnections for several scenarios in future (until 2030). It´s noteworthy to mention that in the test models (analysed scenarios), all the planned HVDC links and North Sea Transnational Grid (NSTG) project have been included depending on their estimated date of completion. A MATLAB based tool has been developed to run power flows with varying wind, load and conventional generation inputs. The results are presented by times series plots of essential result variables such as voltages, branch loadings etc.