Flexible Reactive Power Control in Multigroup Current-Sourced HVDC Interconnections

Self-commutating multilevel current reinjection is a potential alternative to conventional HVDC thyristor technology. An important drawback of the multilevel configurations is the interdependence of the reactive power injections at both ends of the link. This paper describes a new concept applicable to large power converters consisting of two series-connected twelve-pulse groups. It is based on the use of a controllable shift between the firings of the two twelve-pulse groups in opposite directions, a new concept that provides independent reactive power control at the sending and receiving ends. The theory is verified by EMTDC simulation.