Hybrid Grid-Following Control Strategy With DC Inertia Synchronization

Regarding the subsynchronous oscillation issues of grid-following (GFL) converters in weak grids, existing improved control and parameter optimization strategies are already well-developed. Recent references have proposed hybrid control methods that combine features of GFL and grid-forming (GFM) controls. GFL converters applying phase-locked loop (PLL) are liable to instability in weak grids, while GFM converters exhibit good stability. These hybrid structures focus on the integration of virtual synchronous generator (VSG) or droop control with GFL control. Apart from VSG and droop control, DC inertia synchronization (IsynC) control is another common GFM strategy. However, there are currently no published references on hybrid control strategies combining GFL control with DC inertia synchronization. Therefore, this paper proposes an equivalent hybrid strategy for GFL converters by incorporating DC inertia synchronization. The equivalent hybrid method introduces the DC power deviation to the DC voltage loop output, which will influence the d-axis current straightly and q-axis voltage indirectly. Then the PLL outputθwill be consequently affected and finallyθwill include the same component with IsynC, thereby incorporating the concept of equivalent hybrid DC inertia synchronization. Finally, theoretical analysis and experimental results validate the effectiveness of the proposed equivalent hybrid control strategy.