An Accurate Inverter Impedance Estimation Method

Grid-connected inverters are widely used in renewable energy systems. Interaction between the grid and the inverter, however, may generate harmonic resonances that leads to reduced power quality and even instability. To analyze the stability of the inverter-grid system using impedance-based stability criterion, inverter impedance has to be known. This paper proposes an inverter impedance estimation method, which takes into account grid impedance in inverter-grid system and all entries in the impedance matrix. Further, the accurate inverter impedance is obtained. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed method.