Analysis of supraharmonic emission in a microgrid in islanded and interconnected operation

The increasing penetration of distributed generation in microgrids and the connection of different types of electronic loads cause significant levels of supraharmonic emission, especially in islanded microgrids. In this paper loads with different circuit topologies are connected to a laboratory microgrid, and supraharmonic voltages and currents are analyzed in both interconnected and islanded mode. Different indexes were applied to evaluate the supraharmonic emissions in specific frequency bands. Additional combinations of loads are analyzed for the islanded microgrid with regard to different power contributions from the storage and the PV system are assessed to identify the impact of those elements on supraharmonic emission. Finally, measurements of supraharmonic impedance characteristics were performed to find possible causes of the supraharmonic levels, e.g. resonances.