A Solar Charger for Lead-Acid Batteries in an Autonomous PV System

Abstract

Photovoltaic energy is an intermittent energy source because the sun is gone away from evening to morning. Therefore, the batteries have a vital role in getting continuous energy sources for the autonomous system. The battery highly affects the cost of the system. Also, the life span of the batteries can not be sufficient for the consumers. At this point, the charging algorithm is so important because it protects the battery, the battery's life recycling, and the back cost time of the whole system. In this paper, a battery charger is designed to get an efficient autonomous photovoltaic system. The photovoltaic system is designed as two parallel panels, a DC-DC buck converter, and two series batteries. The lead-acid batteries are used because of the lesser cost. The lead-acid battery has three charge regions such as bulk, absorption, and float regions. The bulk region is examined for different irradiation levels in this study because the bulk region is more critical for the system's efficiency. The charge algorithm changes the duty cycle of the buck converter considering the available irradiation level. The photovoltaic charger should satisfy both the maximum power and proper charge operation for the related battery/batteries. The conventional perturb and observe algorithm is modified to eliminate drawbacks such as oscillation around maximum power and the wrong decision law when the irradiation changes. The modified perturb and observe algorithm is used as a photovoltaic charger, and the simulation results present the superiorities of the proposed method.