Simulation and analysis of MPPT used in photovoltaic grid-connected systems based on the improved disturb-and-observe method

The common ideal equivalent circuit of photovoltaic cells is shown in Fig. 1. VD represents an ideal diode, namely the semiconductor PN junction. One part of photo-electromotive force offsets the electric field within the PN junction and recharges the diode. The other part of photo-electromotive force connects to external circuit through the internal resistance in series and in parallel so that the terminal voltage of load RL is U.