Harmonic Emission Assessment of Solar Farms: a Comparative Study Using EMT and Frequency Domain Models

Publication Name

CIGRE Science and Engineering


Large-scale solar farms connected to electricity networks have to demonstrate pre-connection harmonic compliance. To assist this, network service providers use vendor-provided Thevenin/Norton harmonic models of the associated inverters, which are based on off-site tests and modelling. It is questionable as to whether these frequency-domain models can replicate the true behaviour of geographically scattered inverters connected to the point of common coupling via underground cables. The primary objective of this paper is to examine possible discrepancies that can arise in the use of such models by comparing the corresponding outcomes with those established using time-domain models of the inverters. The broad conclusion is that Thevenin/Norton models are unable to reliably predict the true harmonic behaviour in actual operating environments. The study outcomes also support the arithmetic addition of the harmonic currents contributed by the individual inverters to the resultant harmonic current level at the solar farm grid connection point in the absence of resonance conditions.

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