A Power MOS Based Circuit for Controlling the Hot Spot Temperature in Photovoltaic Modules

Localized overtemperature (hot spot) is universally recognized as the main cause of unexpected failure and reliability issues in photovoltaic plants. In fact, the hot spot temperature can be so high to permanently injury the solar panel. Right now, the only countermeasure adopted by solar panel manufacturers is to group solar cells in shorter strings, so that the allowed electrical power in each group is low enough to keep the overtemperature within safe limits. In this paper, a bypass circuit able of controlling power dissipation by modulating the current flowing through the affected solar cell, up to, if applicable, completely cancelling such current. This latter is deviated through a parallel bypass diode (as in standard solar panels), whose possible over heating is in turn prevented by the proper sharing of the current. The correct operation of the circuit is evidenced by means of experiments showing the capability to regulate the overtemperature from zero to the hot spot.