On the effects of interharmonic distortion on grid connected three-phase PV inverters

The effects of interharmonic distortion on Photo Voltaic (PV) inverters whose control is based on the use of PLL systems are analyzed. After some brief recalls on typical PV inverter connection schemes and control strategies, the design of the PLL and its sensitivity to the presence of interharmonic distortion is analyzed. Finally, a case-study on a very simple system is discussed with reference to the Light Flicker phenomenon.

I. Introduction

Power system engineers are used to handle waveform distortion problems by means of Fourier expansion. The presence of interharmonic components has introduced important and new effects in terms of variations in waveform periodicity. A relatively small amount of attention is devoted to the spectral component phase angles in spite of their importance in determining the peak value, the number of zero crossing instants and the delay of the main zero crossing instants with respect to those in sinusoidal conditions, as well as the kind of modulations on the fundamental component. Amplitude Modulation (AM) and Phase Modulation (PM) [1]–[2] of the fundamental component are present in a large variety of situations.