  Interconnecting power converters (IPC) are the main elements enabling the
interconnection of multiple high-voltage alternating current (HVAC) and
high-voltage direct current (HVDC) subgrids. These converters can be classified
either as grid-forming or grid-following. These roles can be assigned to both
ac and dc terminals. This work compares state-of-the-art single-port
grid-forming and grid-following control schemes with a dual-port grid-forming
control scheme, which can simultaneously form a stable voltage on the ac and
the dc sides. The dual-port grid-forming small-signal stability and dynamic
behavior under fluctuations in the power flow are studied and compared against
state-of-the-art control architectures. Moreover, the dual-port control scheme
is validated and tested on a down-scaled laboratory platform with several
transient events.
