Stability analysis of grid-forming direct-drive wind turbine considering source characteristics

Abstract:

To accurately describe the dynamic characteristics of grid-forming direct-drive wind turbines and analyze their stability under different grid strengths, this study considers the source-side characteristics of wind turbines and conducts small-signal modeling of the system. First, based on the state-space modeling method, a comprehensive small-signal model of the entire grid-forming direct-drive wind turbine system with virtual synchronous generator (VSG) control is constructed, and its accuracy is verified through simulation tests. Second, eigenvalue-based modal analysis is employed to investigate the impact of different grid strengths on system stability and assess its adaptability in weak grid environments. Additionally, the mechanism of low-frequency oscillations induced by wind speed step disturbances is analyzed, along with the effects of system structural parameters (such as DC-side capacitance) and controller parameters on the systems dynamic performance. Finally, an RT-LAB hardware-in-the-loop simulation platform is used to build the system model, validating its response capability and accuracy in real-time simulation environments. The results indicate that grid-forming direct-drive wind turbines exhibit strong adaptability in weak grid conditions but may prompt low-frequency oscillations under wind speed step disturbances. Moreover, properly adjusting system structural parameters and optimizing controller parameters can effectively suppress low-frequency oscillations and enhance system stability in weak grid environments. This study provides a systematic modeling approach for analyzing the dynamic characteristics of grid-forming wind turbines and offers theoretical support for further optimizing their stability control strategies.