Study of the effects of non-linear inductance on the performance of resonant and repetitive controllers

Resonant and repetitive controllers are well suited for single-phase photovoltaic systems due to the optimum tracking and harmonics rejection capability. In this paper the effects of non-linear inductance on the performance of current controllers based on the IMP are investigated. When the inductance is non-linear a distorted current waveform is produced; it contain only odd harmonics if the saturation is symmetric. A detailed time-varying model of non-linear inductor has been developed considering two different non-linearities: saturation for high currents and a light non-linearity which occurs in the first portion of the magnetization curve for very low currents. The robustness of the current controllers has been tested. Experimental results have been obtained with two different inductors of two main families: powdered metal core and ferrite core. It has been proven that the resonant and repetitive controllers are able to mitigate harmonic distortion introduced by the non-linearities and to ensure the IEEE 929 standard compliance