Voltage Grid Supporting by Using Variable Structure Adaptive Virtual Impedance for LCL-Voltage Source Converter DG Converters

This article proposes a voltage grid supporting applied for DGs based on LCL-VSC to control the delivered power flow and improve the point of common coupling (PCC) voltage regulation. A variable structure adaptive virtual impedance (VS-AVI) imposes the required DG impedance for achieving the system voltage requirements, considering the power rating of the DG converter. Differently of the solutions presented in the literature, the proposed VS-AVI employs adaptive piecewise linear droop function and dead zone for emulating the virtual capacitance for shaping the equivalent grid impedance and achieves the required PCC voltage regulation. Simulation and experimental results validate the proposed VS-AVI and demonstrate its effectiveness.