An electric circuit model of photovoltaic panel with power electronic converter

Abstract

An equivalent electric circuit model is used to interpret the dynamic behavior of a photo-voltaic (PV) panel with a power electronic converter. The power electronic converter used for maximum power point tracking (MPPT) draws rippled currents from the PV panel. The circuit model is derived on basis of the static single-diode model, in which, the threshold voltage is approximately identical to the voltage at the maximum power point (MPP). An additional parasitic capacitance is introduced to account for the dynamic characteristics as the instantaneous current goes beyond the MPP. The parasitic capacitance dominates the dynamic voltage-current (V-I) characteristics whereas the PV voltage is less than the threshold, meaning that the diode is at the cut-off state. The circuit parameters of the model can be obtained simply from few test points without the need of the intrinsic parameters of the PV panel given by datasheets. Experimental tests are carried out on a laboratory system with a PV panel attached by a boost converter. The dynamic electric circuit model has been demonstrated to be capable of interpreting the dynamic responses of a PV panel under stable illumination.