Microprocessor based load voltage regulator for photovoltaic systems

Abstract

A conventional photovoltaic (PV) system driving a d.c. load consists of a PV array, storage battery, a battery voltage regulator (BVR) and a load. According to this arrangement, the load voltage is equal to the battery voltage. The battery voltage varies according to its state of charge (SOC). 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. Such voltage variations are accepted for many d.c. loads. However, critical loads, such as some communication systems, require a regulated voltage, hence such battery voltage variations are not accepted for these applications. The conventional solution of this problem is to operate the PV system at a 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 loss. In this work, an alternative solution based on a microprocessor that keeps the load voltage at the predetermined level is discussed. The proposed technique avoids the power loss, and as a result, the required PV array size becomes smaller. Hence, the system economics are improved.