Analytical and experimental analysis of buck-boost DC-DC converter in photovoltaic (PV) maximum power point tracking application

Abstract

Renewable energy has emerged throughout the world including Malaysia. One of the renewable energy sources is solar energy where the energy from solar (sunlight) is converted into electrical energy. However, the electricity generated from Photovoltaic (PV) module cannot be guaranteed to operate at maximum power if the PV modules or array are connected directly to the load. To overcome this problem, a method called Maximum Power Point Tracking (MPPT) is normally utilized in PV systems to ensure maximum power extraction. MPPT method consists of a DC-DC converter that is connected in between the PV generator and the load. The operating point of the system is controlled by varying the duty cycle of the converter. In this project, a DC-DC Buck-boost converter is employed as the MPP tracker to ensure continuous extraction of maximum power from a PV system at various environmental conditions. This converter is selected based on its ability to match the PV module impedance independence of the load and irradiance. Simulation and experimental analyses on the developed Buck-boost DC-DC converter is performed at irradiance level of 100 W/m2 to 1000 W/m2. A CHROMA PV Simulator (Model: 62100H-600S) is used to emulate 4 PV modules (MSX-60) connected in series. EZDSP F28335 Digital Signal Processing (DSP) is employed as a controller to control the duty cycle of the converter. Results showed that the developed converter is able to track the MPP for all irradiance levels tested. The simulation and experimental results are almost similar. In addition, it is proven that Buck-boost converter is able to trace the MPP from 0 V to open circuit voltage, Voc. Hence it should be able to find the correct MPP even during the occurrence of partial shading (PS) conditions in which the correct MPP will not be at its normal range, i.e. 0.7-0.8 times Voc.