Mobile QR Code QR CODE : The Korean Institute of Power Electronics
Title Equivalent Grid Impedance Estimation Method Using Negative Sequence Current Injection in Three-Phase Gridconnected Inverter
Authors Chan-Sol Park ; Seung-Ho Song ; Ji-Hoon Im
DOI 10.6113/TKPE/2015.20.6.526
Page pp.526-533
ISSN 1229-2214
Keywords Grid impedance estimation; Equivalent grid impedance; Negative sequence current injection; Grid-connected inverter; Unbalanced voltage
Abstract A new algorithm is proposed for the estimation of equivalent grid impedance at the point of common coupling of a grid-tie inverter output. The estimated impedance parameter can be used for the improvement of the performance and the stability of the distributed generation system. The estimation error is inevitable in the conventional estimation method because of the axis rotation due to PLL. In the conventional estimation error, the d-q voltage and current are used for the calculation of the impedance with active and reactive current injections. Conversely, in the proposed algorithm, the negative sequence current is injected, and then the negative sequence voltage is measured for the impedance estimation. As the positive and negative sequence current controller is independent and the PLL is based on the positive sequence component only, the estimation of the equivalent impedance can be achieved with high accuracy. Simulation and experimental results are compared to validate the proposed algorithm.