Extended coupled Norton model of modern power-electronic devices for large-scale harmonic studies in distribution networks

Abstract

The increasing application of non-linear power-electronic based devices in low voltage networks might have a negative impact on power quality, particularly on harmonics. To estimate the harmonic levels or to identify possible resonances, respective network simulations involving a large number of power electronic devices are necessary. These require realistic device models, which need to represent both the harmonic emission and the input admittance characteristic, as otherwise simulations might not converge or result in unrealistic results. While many proposals exist for harmonic emission models, not much approaches can be found regarding the input admittance. This study intends to fill this gap and presents a modelling approach combining the harmonic emission and the input admittance characteristic in a single model. Therefore, the classic Norton model is extended by a generic circuit-based part, which consists of linear, passive components and is parameterised based on measurements. The extended Norton model is applied to six photovoltaic inverters and 18 electric vehicle chargers and its application are demonstrated in a harmonic simulation.