Chapter 1 was extensively dedicated to the discussion of the main aspects concerning the current vs. voltage characteristics of a PV generator and its dependency on the exogenous uncontrollable temperature and sun irradiance variables. The in-depth analysis has shown evidence that the joint variation of temperature and irradiance, as well as the occurrence of drift phenomena that arise along the PV system lifetime, about 25 years, makes the position of the maximum power point (MPP) varying in a wide area. As a consequence, a direct connection of the PV generator to the input port of a power processing system imposing a constant voltage level would be a simple but poor choice from the energy productivity point of view. For instance, a PV battery charger obtained by connecting merely the PV array terminals to the battery would force the PV generator to work at a constant voltage. If this voltage is higher than the PV array open-circuit voltage, then the PV system does not deliver any electric power. Otherwise, the closer the battery voltage to the actual VMPP , the higher the electrical power generated by the PV array. Unfortunately, due to the inherent time variability of VMPP caused by the changes in the operating conditions, the probability that the PV array delivers the maximum power at any time of the day is almost near zero.