Analysis of the effects of inverter ripple current on a photovoltaic power system by using an AC impedance model of the solar cell

Most of the solar cell models suggested so far mainly employ steady state modeling methods to estimate the characteristic I-V curve of a solar cell at a certain operating point. Thus a study on the dynamic characteristics of a solar cell can rarely be found. For the design of a high performance power conditioning unit, it is essential to have accurate information about the static and dynamic characteristics of the solar cell. In this study an AC impedance model of a solar cell module is developed using Impedance Spectroscopy and it is then used for evaluating the effects of the ripple current generated by a single phase inverter. Experimental results verify that the energy conversion efficiency of a photovoltaic power system may be significantly reduced when the 120 Hz ripple current generated by a single phase inverter is larger than a certain value and an appropriate limit value for the 120 Hz ripple current is also suggested.