Effects of different control strategies of distributed generation on the equivalent output impedance of the grid-connected inverter

This paper focuses on the effects of different control strategies of the distributed generations (DG) on the equivalent output impedance of the grid-connected inverter under different operating conditions of microgrid. For grid-connected inverter with LCL filter, two equivalent impedance models using PQ and V/f control were deduced in detail respectively, meanwhile the spectrum response curves of these two kinds of impedance under typical parameters were drawn. The different characteristics of the inverter output impedances between PQ control mode and V/f control mode were compared and analyzed. Finally, under the situation of grid-connected and islanded operation of microgrid, simulation researches of DG equivalent impedance with and without consideration of the inverter control mode on the current harmonic characteristics of each node were carried out, and the validity of the proposed method was verified.