Transient Synchronization Stability Analysis of Grid-forming Converter Influenced by Power-coupling and Current-limiting
In the grid-forming(GFM)converter with the limiting output current,power-coupling between active and reactive loops and current-limiting between voltage and current loops can significantly affect the synchronous process of the converter with power grid.Therefore,this paper studies the transient synchronization stability of GFM converters influenced by power-coupling and current-limiting.First,considering these two factors,the reduced-order model of the converter is established.Then,an energy function,containing three state variables(power angle,frequency and voltage)of the GFM control,is constructed.Based on Lasalle's theory,the domain of attraction of the converter and its corresponding transient stability margins are obtained.The analysis results reveal that power-coupling and current-limiting deteriorate the transient synchronization stability of the converter by affecting the distribution of potential energy and damping,respectively.Thus,based on virtual impedance and power decoupling,an optimized strategy for GFM control is proposed to suppress these negative effects from power-coupling and current-limiting.Finally,simulation and experimental results verify the correctness of the above theoretical analysis.
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