Characterisation of supraharmonic emissions based on phase angle representation methods

Power electronic interfaces in solar PV inverters generate high-frequency harmonic emissions, also referred as ’supraharmonic’ emissions, due to the fast switching (above 2 kHz) required to create low distortion output waveforms. Measuring and evaluating these emissions is a new challenge for power quality experts, as present standards (IEC, CISPR) do not include prescriptive measurement and analysis techniques for the entirety of this range (2–150 kHz). This paper investigates supraharmonic emissions from identical solar PV inverter systems highlighting distinct frequency zones to distinguish phenomenon types. The existing high-frequency harmonic measurement method given in IEC 61000-3-6 with some enhancements has been used to characterise supraharmonic emissions. This paper proposes three methods to represent the phase angle for grouped supraharmonic emissions that assist in understanding their diversity. In terms of aggregation of emissions, field measurements indicate that a summation exponent (α) equal to 1 should be applied for resonant emissions, while for switching frequency emissions, circulation between sources leads to harmonic cancellation.