Conventional grid-code specifications for dynamic ancillary services
provision such as fast frequency and voltage regulation are typically defined
by means of piece-wise linear step-response capability curves in the time
domain. However, although the specification of such time-domain curves is
straightforward, their practical implementation in a converter-based generation
system is not immediate, and no customary methods have been developed yet. In
this paper, we thus propose a systematic approach for the practical
implementation of piece-wise linear time-domain curves to provide dynamic
ancillary services by converter-based generation systems, while ensuring
grid-code and device-level requirements to be reliably satisfied. Namely, we
translate the piece-wise linear time-domain curves for active and reactive
power provision in response to a frequency and voltage step change into a
desired rational parametric transfer function in the frequency domain, which
defines a dynamic response behavior to be realized by the converter. The
obtained transfer function can be easily implemented e.g. via a PI-based
matching control in the power loop of standard converter control architectures.
We demonstrate the performance of our method in numerical grid-code compliance
tests, and reveal its superiority over classical droop and virtual inertia
schemes which may not satisfy the grid codes due to their structural
limitations.Comment: 7 pages, 9 figure