Comportamento de conversores fonte de tensão e filtro LCL na presença de harmônicos na rede

Abstract

The increase of the number of power electronics converters connected to the grid has raised concerns about power quality issues, most specifically harmonics. In this thesis, it is analyzed the behavior of grid interface unities comprising a voltage source converters with current control and LCL (inductor-capacitor-inductor) filter with passive damping in the presence of background harmonics. The aim is to clarify the causes of harmonic distortions at the point of connection and support the development of solutions and improvements in grid-connected converter technology. An analytical expression of the equivalent impedance of the interface unity seen by the grid is defined. The expression is used to assess the main characteristics that may result in low impedance at some critical harmonic frequencies seen by the grid. Generally, the converter of the grid interface unity is seen as the harmonic source, however, this current thesis shows it may be absorbing background harmonic from the grid and not only injecting.