Synchronization Stability Control Scheme for Converters Based on Dynamic Voltage Feedback

Grid-following voltage source converter (GFL-VSC) relies on phase-locked loops (PLL) to maintain synchronization with the grid, and faces the risk of PLL synchronization instability due to the reduction of grid transmission limit during grid fault ride-through. To address this problem, a PLL synchronization stability control scheme for converters based on dynamic voltage feedback is proposed, which can significantly improve its PLL synchronization stability during grid fault. Firstly, the equivalent swing equation of GFL-VSC based on PLL synchronization is established, and the internal mechanism of synchronization instability of GFL-VSC during fault ridethrough is elucidated by the equal area criterion (EAC) in the existence of stable equilibrium point (SEP); Secondly, a PLL synchronization stability control scheme based on dynamic voltage feedback is constructed on this basis, which can slow down the acceleration process of PLL and improve the PLL synchronization stability of the converter based on the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$q$</tex>-axis voltage feedback to adaptively adjust the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$d$</tex>-axis current reference value during grid fault. Finally, the effectiveness of the proposed control scheme is verified by simulation.