  Recently, the authors of this paper proposed a method for the Harmonic
Power-Flow (HPF) calculus in polyphase grids with widespread deployment of
Converter-Interfaced Distributed Energy Resources (CIDERs). The HPF problem was
formulated by integrating the hybrid nodal equations of the grid with a
detailed representation of the CIDERs hardware, sensing, and controls as Linear
Time-Periodic (LTP) systems, and solving the resulting mismatch equations using
the Newton-Raphson (NR) method. This work introduces a novel problem
formulation based on the fixed-point algorithm that, combined with the
contraction property of the HPF problem, provides insights into the uniqueness
of its solution. Notably, the effectiveness of the fixed-point formulation and
the uniqueness of the solution are evaluated through numerical analyses
conducted on a modified version of the CIGRE low-voltage benchmark microgrid.
