Sammendrag
This paper compares the impact on power system
frequency transients from virtual inertia and Fast Frequency
Reserve (FFR) provided by HVDC converters. Specifically,
frequency nadir, Rate-of-Change-of-Frequency (RoCoF), and
the required energy during the frequency support are
evaluated. Two control schemes for providing virtual inertia are
considered, including a current controlled Virtual Synchronous
Machine (VSM) and a grid-following control with frequency
derivative-based inertia emulation. The studied FFR provides
either short or long support according to the guidelines of
the Nordic synchronous area. Simulation studies are conducted
in DIgSILENT PowerFactory using a 44-bus simplified model
of the Nordic power system. With the same peak power, the
results show that the different strategies have similar impact
on the frequency nadir, while only the virtual inertia improves
the RoCoF. Furthermore, the strategies for virtual inertia
support can provide improvement of the frequency nadir with
significantly less injected energy than the FFR long support
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