Stability control method based on virtual inductance of grid-connected PV inverter under weak grid

High impedance characteristics of weak grid can easily lead to some problems such as poor stability of photovoltaic (PV) power generation system, high grid-connected current harmonics and so on. For solving these problems, this paper establishes a system stability criteria based on impedance matching for current-source PV power generation system, deduces the output impedance model of single-phase grid-connected PV inverter, and studies the impact of weak grid on inverter stability and grid-connected current harmonics. Then proposes a control method based on virtual inductance for increasing the output impedance of inverter to improve the system stability, and adopts a grid synchronization method based on second-order generalized integrator phase locked loop (SOGI-PLL) to improve the quality of the grid-connected current. Finally, simulation and experimental results verify that the proposed method can effectively improve the stability of PV grid power system and reduce the grid-connected current harmonics under weak grid.

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