Dynamic and steady-state characteristics of dc machines fed by photovoltaic systems

This paper presents the dynamical model and analysis of DC shunt, series and permanent-magnet (PM) motors fed by photovoltaic (PV) energy systems at different illuminations. At the full solar intensity, the maximum power point of current/voltage (I/V) characteristic of the PV modules is designed to be at the rated conditions of the machines. The nonlinear behaviour of I/V characteristics of the PV modules and that of the magnetization curve of the ferromagnetic materials of the machines are approximated by polynomial curve fitting. The dynamical analysis of the machines fed by fixed terminal voltage has also been carried out and a comparison between the cases of supplying the motors by fully illuminated solar cells, partially illuminated solar cells and fixed terminal voltage is addressed. The steady-state output characteristics, and the torquespeed characteristics, of the three DC motors with the two inputs are presented and compared. All the simulations are executed using MATLAB.