Reference Grid Impedance for Tests of Grid-connected Power Converters for Distributed Energy Resources: The Brazilian Case

The Brazilian standard ABNT NBR 16149 defines the tests and procedures for the connection of photovoltaic inverters to the low voltage electrical grid. According to the ABNT NBR 16149, the flicker tests must be performed based on the international standards IEC 61000-3-3, IEC 61000-311 and IEC 61000-3-5, wich define a reference impedance for the equipment connection to the low voltage grid. However, the Brazilian grid presents different voltage levels and transformer configurations, so that the reference impedance defined in the international standards are not always compatible with the Brazilian systems. In this sense, this paper proposes a new classification for the inverters, according to the voltage levels and characteristics of the grid. A new reference impedance is also proposed and simulation results are included to demonstrate the impact of this choice for the operation and tests of grid connected inverters.