Grid-Forming Based SVG to Mitigate Sub-Synchronous Oscillations of Offshore Wind Farms in South China

This paper introduces grid-forming (GFM) based SVG to mitigate sub-synchronous oscillations (SSOs) of the offshore wind farms in South China. In September 2023, two SSO events were observed in the commissioning stage of four SVGs equipped with the offshore wind farms, and the cause of these two SSO events is preliminarily attributed to interactions between the SVGs with traditional gird-following (GFL) control and the weak grid. It is known that the GFM-based SVG emerges as a promising solution to mitigate such SSOs. However, the conventional GFM control algorithms suffer from instability issue in stiff grids. To overcome such limitation, an enhanced GFM control with the hybrid synchronization and asymmetric vector-voltage control is proposed in this work. Such enhanced GFM control provides more damping in stiff girds, which, thus, makes the SVG achieve stable operation in a wide range of SCR. The impedance-based stability analysis together with the PSCAD/EMTDC simulation results is presented to demonstrate the effectiveness of the GFM-based SVG in solving the SSOs.