Abstract:The grid shows the characteristics of weak grid due to scattered high power distributed power generation device. The grid impedance will affect the robust stability of the grid-connected inverters and lead to harmonic resonance as well as the instability of the system. The output impedance model of LCL-filtered single-phase grid-connected inverter was derived, and the study of stability based on impedance analysis was presented in the paper. In order to increase the phase margin of the grid-connected inverters, a novel impedance phase compensation control strategy was proposed, and the detailed implementation and parameter design of the impedance phase compensation control method was depicted. The effect of PLL loop, digital control delay, and the impedance phase compensation control on the output impedance characteristic was analyzed in quantity. The fundamental frequency phase effect of impedance phase compensation control was also analyzed. Finally combining impulse response based grid impedance online measurement and the impedance-phased dynamic control scheme was introduced, and the effectiveness of the impedance-phased dynamic control was verified by experiment.
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