Supraharmonics Emission Assessment of Multi-level Converters Applied for Photovoltaic Grid-Connected Inverters

Abstract

Topologies for different DC-AC converters used on grid-connected photovoltaic (PV) inverters are analysed and compared within this paper. The main focus is to evaluate the supraharmonic emission in the frequency range 2 to 150 kHz. For this study three topologies are evaluated: Neutral Point Clamped (NPC), the Cascaded H-bridge (CHB) and the Flying Capacitor (FC). To approximate the operation closer to a real scenario, the converters are analysed under the presence of voltage waveform distortion in the power supply. The simulation is performed using PSpice for the converters and Simulink for the grid. The characterization is made by the quantification of harmonics and supraharmonics, and also by the frequency domain analysis of the output current. Finally, a comparison of the chosen technologies is carried out, given a better understanding on the elements which exert influence on this type of emission.