Methodology for experimental determination of equivalent grid impedance by using external commands of PV inverters

Abstract

Equivalent grid impedance is an important information for testing control stability of grid-connected inverters. Furthermore, grid impedance parameters impact on local grid voltage when the local load or generator changes its active and reactive power. In grid connection standards such as the Brazilian Association of Technical Standards (ABNT) Brazilian Regulatory Standard (NBR) 16149, Photovoltaic (PV) inverters higher than 6 kW shall have external control of active and reactive power. This manuscript proposes a methodology for experimental determination of grid impedance by using the external commands of PV inverters. Experimental results were obtained with a 100 kW inverter of a photovoltaic power plant, and then the local grid impedance was calculated. Finally, the impedance calculation was validated in simulation.