A current flow controller for use in HVDC grids

Early proposals for multi-terminal HVDC interconnections have been predominantly radial type connections, that is, between any two nodes there is only one branch. However, plans for `HVDC Grids´ in the not too distant future are, or include, meshed sections where there are parallel branches between nodes in the HVDC Grid. In such meshed HVDC Grid the DC current will inherently flow from one node to another via the path of least resistance. However, this may mean that one branch within the HVDC Grid becomes overloaded, hence, power flows across the HVDC Grid may have be constrained in order to keep all branch loadings within their rating. In order to avoid the need to apply constraints a number of solutions have been proposed to date and these are discussed here.