Comprehensive and Robust Parameter Design of Grid-Forming Converter with Inner Dual-Loop under Weak Grid Condition

With a high penetration level of renewable energy into grid, the grid-forming (GFM) converter is attached great importance to overcome the instability of grid-following (GFL) converter under weak grid condition. However, synchronous resonance and LC resonance may occur in GFM converters, which threatens the stability of power system. To deal with the problem, this paper focuses on the small-signal modeling and parameter design of GFM converter with inner dual-loop. The small-signal modeling of inner dual-loop is given and it is regarded as an output impedance for power loop analysis. Further, the simplified single-in-single-out (SISO) small-signal model of the power loop is derived. Based on the model, a step-by-step parameter design method is proposed to facilitate the design of control parameter. With the proposed parameter design method, the synchronous resonance and LC resonance can be depressed. Finally, simulation and experimental results are given to verify the theory and the proposed parameter design method.