4. Direct feed

Decarbonization requires much more demanding performance in terms of flicker reduction than shunt solutions such as SVC or STATCOM, or the mixed solution, can achieve. So the serial solution begins to appear. There are two types of series solution: the back-to-back solution and the UPFC/UPQC solution.

The back-to-back solution consists of an MVDC converter with AC/DC conversion followed by DC/AC conversion with intermediate DC medium-voltage circuitry. MMC technology makes it possible to achieve the high power levels required, with the advantage of modularity, intrinsic redundancy, etc.

The UPFC/UPQC solution (figure 45 ) combines a shunt and a series solution on the same DC medium-voltage intermediate circuit. The shunt...