A conventional photovoltaic (PV) system driving a DC load consists. of a PV array ,storage battery. a battery voltage regulator (BVR) and a load The voltage of typical lead acid batteries. widely used in PV systems, varies between 93 5 % and 120% of its nominal voltage according to its state of charge (SOC) such voltage variations are not accepted for critical loads such as some communication systems Conventional solution of this problem is to operate the PV system at higher voltage and to include a control circuit that introduces passive elements so that the load is operating within the allowed limits. Such a solution leads to power dissipation in the passive elements and this presents power toss.
In this work an alternative solution based on a microprocessor that keeps the load voltage at the predetermined level is discussed. The system consists of an A/D converter, a microprocessor controller, a switching circuit and a filter. The microprocessor reads the battery voltage variations via the A/D converter corresponding duty cycle value is calculated and used to control the switching circuit to achieve the required regulation. A detailed simulation program is used to study the performance of the PV system installed in Cairo city. The proposed technique avoids the power loss and as a result the required PV array size becomes smaller. Hence the system economics is improved.