Behavior of the Grid Connected Converter in Unbalanced Smart Power Systems

Even with power electronic converters in almost every grid connected device, there are still several looming questions ahead, especially in regard to previously very rigid operating conditions. With the integration of non-linear consumers and inverter based distributed energy resources, the balanced nature of the power system may be impaired leading to asymmetrical voltages at the points of common coupling. This is particularly true for islanding and smart grid application. This paper aims at presenting the behavior of grid connected converter under asymmetrical voltages in unbalanced power systems. Detailed analysis of the asymmetrical voltage influence on key control aspects will be presented within the paper. The results for classically controlled grid connected converter operating under asymmetrical voltages at the point of common coupling will be presented. Special attention will be given to the influence of voltage asymmetry on important aspects of the control such as phase-locked loop and current controller.