The Transistor Based Direct and Reverse Mode Model for Photovoltaic Strings and Panels

AbstractPhotovoltaic generators involve many systems operating together. The illumination on a PV generator (PVG) is neither homogeneous nor constant. Some fluctuations in the illumination intensities and spectra, due by example to shadows, with various dynamic, can occur on the PV panels which constitute a big problem for the inverter to determine precisely the position of the Maximum Power Point (MPP) for an optimal and efficient power transfer. So it is very important to analyse the dynamics behaviour of such systems by using electronic simulation tools like ORCAD®, PROTEUS® etc. It is also interesting to consider the possibility to connect PV panels to smart DC/DC converters in order to provide a High DC Voltage (HVDC) bus. The goal of the present paper is to determine very precisely the dynamic response of a PV system with a high global efficiency. In order to easily simulate a global system including PV panel(s) converter(s) and load, with consideration of small partial shading onto the surface, it is advantageous to minimize the number of basic components in the schematics used for the simulation. This allows a better computing convergence on a short simulation time. In the present contribution, a novel global model representing the behaviour of a string, a panel or a PVG in Direct and Inverse biasing modes is studied. Moreover, this model gives a good restitution of a PVG behaviour in case of partial shading. It is also compared with a standard string of photovoltaic cells. The solar-cell model used for this study is a Direct and Reverse Mode (DRM) model, published in previous paper, which integrates the second quadrant corresponding to the reverse operating mode. In partial shading of PV systems the proposed model allows to have a good approximation of the I-V characteristics curves on PV panels with easier an efficient simulation