Projeto e simulação de um sistema fotovoltaico conectado à rede

Abstract

In addition to other benefits, the sun provides radiated energy that can be converted into useful electrical energy through photovoltaic (PV) modules. For this energy to become useful in most loads and electronic devices, the PV power in the direct voltage and current forms must be transformed into alternating voltage and current forms, meeting the requirements of the local power grid distribution. In the vast majority of grid-connected photovoltaic system topologies, the first stage of electrical energy transformation is carried out by a DC/DC converter, which increases the voltage of the PV modules, and, at the same time, promotes the maximum photovoltaic power tracking (Maximum Power Point Tracking - MPPT). For this, the MPPT algorithm must compute in real time the optimum duty cycle of the DC/DC converter for the maximum power injected in the DC bus. In a second stage of electrical energy conversion, a DC/AC converter allows the energy injected in the DC bus to be transferred to an AC power grid with fixed voltage and frequency. The DC/AC converter is composed of switched devices(transistors with antiparallel diodes) that act so that the injected AC current is very approximately sinusoidal and in sync with the grid voltage. For this to be possible, it is necessary that a part of the control performs the function of detecting the frequency and phase of the grid voltage. A closed loop control, commonly known as Phase Locked Loop – PLL performs this function. This work presents details of design, simulation and dimensioning of a single phase grid-connected photovoltaic system, as well as fundamental concepts for understanding the control, tracking and synchronization algorithms with the electrical grid.