On harmonic emission assessment: a discriminative approach

Abstract

An improvement in the assessment of harmonic emissions as contributed by renewable generation such as a Photovoltaic (PV) plant, at a Point of Connection (PoC) to a distribution network, is needed. Both the generating source and the distribution network contribute to the voltage harmonic distortion at the PoC and single-point measurements cannot be used to quantify the relative contributions of each source. IEC 61000-4-30 Class A PQ measurements are used as a reference dataset for engineers and can be obtained simultaneously at different points in a network in an attempt to better understand the relative contribution by the source of distortion and the voltage supply network. The opportunity to improve the CIGRE/CIRED C4.109 approach by means of multiple-point synchronized network data is shown to be significant in the qualification of the statistical method but lacks the quantification in calculating the harmonic emission of a non-linear load. The CIGRE/CIRED method can be improved by only considering those harmonic currents identified as emission as some harmonic currents could be the result of background harmonic voltages in the supply network. Constraints in using IEC 61000-4-30 time-aggregated rms voltage and current values to support the assessment of harmonic emission using field-measured data is lastly shown as the calculation method and measurement uncertainty influence the compliance to grid code requirements on harmonic emissions