Modeling and Evaluation of MPPT Methods for a Three-Port Converter Used in PV Applications

Abstract

Worldwide energy demand is growing fast because of the population explosion. Technological advancement paved the way toward utilizing renewable energy sources instead of fossil fuels as they cause harmful effects on the environment. Among all renewable sources, solar energy is a promising source. Solar energy is captured by photovoltaic (PV) arrays that convert the sunlight into electricity that powers the load. Since sunlight is not always available, a battery is utilized to power the load as a backup power source. Both PV and battery are interfaced with the load using a power converter. A Three-Port Converter (TPC) has recently gained interest in the literature. The TPC interfaces the PV and the battery with the load. It is less expensive and more efficient than using two separate power converters for the PV and the battery. However, a system with TPC connecting a PV array and a battery to a load could be further enhanced by applying Maximum Power Point Tracking (MPPT) techniques to the TPC. By applying MPPT, the PV arrays are guaranteed to operate at the maximum power they can deliver. This thesis aims to simulate a system with a TPC and apply different MPPT techniques (Perturb and Observe P&O and Incremental Conductance (IC) to the TPC. Based on the resultant simulation, these techniques are compared based on their response to the environmental changes (radiation and temperature) to identify the most suitable MPPT technique for a TPC. The topological structure of the TPC is identified based on a comparison with the available TPC topologies. The comparison is based on topology complexity, efficiency, and control complexity. To achieve this aim, three steps are followed. The first step is simulating a case study of an existing PV system is considered to illustrate the importance of applying MPPT to PV systems. Namely, the PV system installed at Effat library rooftop is simulated using MATLAB/SIMULINK with and without the MPPT. The simulation shows that applying MPPT increases the system efficiency up to 99%. The second step compares the PV power of a system of the two-port converters and a system of TPC when the solar irradiance changes. In the last step, TPC is simulated in MATLAB/SIMULINK, and MPPT methods (P&O and IC) are applied. Based on the simulation, both MPPT methods exhibit similar results when the radiation and temperature change. However, the IC method performs slightly better than P&O. Hence, IC has a better response to environmental changes than P&O. The significance of this work relies on enhancing TPC used in PV applications by applying MPPT. This field has not been much investigated in the literature.