Experimental investigation of mirror frequency currents emitted by low voltage inverters under distorted grid voltage conditions

In the context of fundamental changes in the electricity, mobility and heat sectors, an increasing share of power electronics based components is integrated into low voltage grids. As they are based on inverters and control circuits, these components usually have nonlinear characteristics, and the feedback of a distorted voltage onto the current emission has yet to be investigated. In this work, the frequency behavior of two commercially available low voltage inverters is measured under different distorted voltage conditions and operating points. In order to illustrate the current responses, a modified spectrogram visualization technique is introduced. The results show that a nonfundamental disturbance in the grid voltage can cause several nonfundamental current components that are emitted by the inverters. When analyzing the dependency of operating points on the current response to a disturbance, only a low dependency can be determined. The significant differences found between manufacturers empherzizes the need for experimental measurements and black-box models that capture this behavior. Furthermore, inclusion of emissions under distorted grid voltage conditions in future standards should be discussed.