Harmonic emission of PV inverters under different voltage supply conditions and operating powers

This paper presents the results of experimental evaluation of current harmonic emission characteristics of three photovoltaic inverters (PVIs) under different voltage supply conditions and for full range of their operating powers. In tests, various voltage supply conditions are emulated with both ideally sinusoidal and typically distorted voltage waveforms, as well as with different source impedance values, while power outputs of PVIs are adjusted in the range from their nominal/rated powers down to the lowest possible powers at which they were able to maintain a stable operation. Harmonic emission of tested PVIs is quantified in terms of their total harmonic content, total harmonic/demand distortion and individual current harmonics, which are compared with the corresponding emission limits in existing standards and recommendations. Particular attention is given to the 2nd-7th low-order harmonics.