A Study on the Complex Remodeling Strategy of Output Impedance of LCL-Type Grid-Connected Inverters under Weak Grids
Under the influence of the grid voltage proportional feed-forward and phase-locked loop(PLL),changes of grid impedance wide-range can easily lead to instability of the grid-connected inverter.For this reason,this paper firstly establishes an output impedance model of the grid-connected inverter with the influence of the grid voltage proportional feed-forward and PLL considered,and analyzes the system stability with the help of impedance stability criterion.Furthermore,the paper proposes a composite impedance remodeling strategy based on the grid voltage feed-forward.In addition,the output impedance of the grid-connected inverter is reshaped to improve the stability of the grid-connected inverter by connecting a low-pass filter in series in the grid-voltage proportional feed-forward link as well as adding a grid-voltage feed-forward branch to eliminate the influence of PLL.Finally,the results of simulation and experimental verification show that the proposed impedance reshaping strategy can effectively improve the stability of grid connected inverters under wide range impedance changes,and improve the quality of the grid connected current.
inverterphase-locked loopgrid voltage feed-forwardimpedance remodelingweak grid
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