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The insertion of photovoltaic solar energy has increased considerably over the past few years, with remarkable growth since 2005. It is essential that the electrical energy delivered by the photovoltaic system to the grid has an acceptable quality level. This paper presents test results of power factor and harmonic distortion content in grid connected inverters for photovoltaic systems. Several tests of ten commercially available inverter models from three different manufacturers were performed at the Laboratory of Solar Energy (Labsol) at the Federal University of Rio Grande do Sul (UFRGS), using a test bench with a power analyzer. The power factor and total harmonic distortion in current curves were mathematically modeled as a function of relative power in order to be used in computer simulation of photovoltaic systems. For power loads close to the nominal values, the harmonic content was found to be low and in accordance with the standard requirements. Nevertheless, at low loading levels the inverters may inject high levels of harmonics into the grid. [ABSTRACT FROM AUTHOR]

The application of photovoltaic (PV) as a source of electrical energy in the distributed generation (DG) systems are gaining more attention with the advances in power electronics technology. The one of the key technologies in the PV based DG systems is grid connected inverter that is utilized to interface PV power systems into the utility grid. Multilevel multifunctional grid connected inverters (ML-MFGCIs) are new breed of power converter used in large scale PV applications and have superior advantages such as lower switching power dissipation, lower harmonic distortion and lower electromagnetic interference (EMI) outputs. ML-MFGCIs perform the high quality power from PV systems and provide flexible functionality with improved power quality (PQ), voltage and reactive power support and increased capability of the auxiliary service for the utility grid. This paper presents a detailed analysis of various ML-MFGCI configurations for 1-phase and 3-phase systems and control strategies to compensate the different PQ problems. Almost 100 papers including the practical applications and recent research studies on ML-MFGCIs are reviewed and analysed. [ABSTRACT FROM AUTHOR]