2019 IEEE PES/IAS PowerAfrica 978-1-7281-1010-3/19/$31.00 ©2019 IEEE Design of a PV Based Power Supply with a Non- Inverting Buck-Boost Converter Kingsley A. Ogudo Department of Electrical and Electronics Engineering Technology Faculty of Engineering and the Built Environment University of Johannesburg kingsleyo@uj.ac.za Patrice Umenne Department of Electrical and Mining Engineering University of South African (UNISA) Johannesburg, South Africa umennpo@unisa.ac.za Abstract - This paper presents the design of a photovoltaic based power supply using a non-inverting buck-boost converter to charge batteries. The batteries can be used to power a load as back-up power when there is no sunlight. This approach presents a constant output of 48 V charging voltage for the batteries even though the input voltage may vary depending on the amount of solar irradiation falling on the solar panel. Solar charge controllers are important components in such an off-grid system because they can be used to protect the battery bank from overcharging and regulate the charging current. The buck-boost converter is used as a solar charge controller to maximize the charging voltage when the solar irradiation provides less than the required output voltage. The DC-DC converter (buck-boost converter) was modelled using the SIMetrix software to demonstrate the expected output waveforms before building the complete PV power supply. Index Terms - Buck-boost converter, DC-DC converter, Photovoltaic (PV) System, Solar charge controller, SIMetrix software. I. INTRODUCTION Renewable energy such as solar, wind, hydro, biogas and nuclear are many of the promising solutions that can be used to address the lack of access to clean electricity. Renewable energy can help to reduce the greenhouse gas emissions produced by fossil fuels such as coal and diesels. Many rural parts of the continent still lack access to electricity and clean drinking water. As a result, most of these communities, still rely on fossil fuels to perform daily activities such as lighting, cooking and heating. In sub- Saharan Africa and Asia 84% of people lack access to electricity, where majority of these are rural dwellers [1]. Therefore, solar energy is one of the proposed methods of providing cleaner, safer and reliable energy to rural communities, especially where communities are not connected to the power grid. Solar energy is free, abundant and cheaper for powering homes with enough energy. This can be achieved by proper planning and execution, through which all the energy requirements may be met cost- effectively [2]. II. METHODOLOGY A. PV Systems Solar panels convert solar energy into electrical energy. Most of the electrical energy is in the form of direct current. The direct current (d.c.) is connected to the solar charge controller for charging the batteries. Photovoltaic systems are classified according to their functionality and method of operation and careful consideration is given to customer requirements. Types of PV systems [3], [4] include grid connected, hybrid system and off-grid systems. Grid connected solar systems are systems which are connected in parallel with the national grid. This solar system utilises an inverter to invert the DC voltage from the solar panels into AC. The hybrid system is a combination of renewable energies (Solar, wind turbines, biogas) which are connected with the aim of providing stable power. In this system sub- components complement one another in such a way that when one component does not supply sufficient power then another component takes over. Back-up storage is also used in this system in the case where renewable sources are not operating in favourable weather condition. Fig.1 shows an example of a hybrid PV system. Fig. 1 Example of hybrid system [5] The off-grid or stand-alone system as the name refers is not connected to the national grid. It supplies its own power during the day and at night and uses batteries as a back up. 