  Power distribution systems experience a large-scale integration of
Converter-Interfaced Distributed Energy Resources (CIDERs). As acknowledged by
recent literature, the interaction of individual CIDER components and different
CIDERs through the grid can lead to undesirable amplification of harmonic
frequencies and, ultimately, compromise the distribution system stability. In
this context, the interaction of the DC and AC sides of CIDERs has been shown
to have a significant impact. In order to analyze and support the mitigation of
such phenomena, the authors of this paper recently proposed a Harmonic
Power-Flow (HPF) framework for polyphase grids with a high share of CIDERs. The
framework considers the coupling between harmonics, but ignores the DC-side
response of the CIDERs. Modelling the DC side and AC/DC converter introduces a
nonlinearity into the CIDER model that needs to be approximated for the
numerical solution of the HPF. This paper extends the CIDER model and HPF
framework to address this aspect, whose inclusion is non-trivial. The extended
HPF method is applied to a modified version of the CIGRE low-voltage benchmark
microgrid. The results are compared to (i) time-domain simulations with
Simulink, (ii) the predecessor of the extended HPF which neglects the DC side,
and (iii) a classical decoupled HPF.
