Fractionally rated transformer-less unified power flow controllers for interconnecting synchronous AC grids

Recently, a novel transformer-less unified power flow controller (T-UPFC) has been proposed. The T-UPFC is a suitable candidate for performing power flow control in interconnected synchronous AC grids. By means of analytical expressions, this paper provides the overall device power rating of such a system when used to control power flow through the line to its limit. By means of these results, it is shown that the ratings of T-UPFC are only a fraction (two tenths) of that of back-to-back VSC based HVDC converter projects commercially being executed to provide power flow control in interconnected synchronous grids. The analysis and results in this paper illustrate the clear benefits of this technology.