An Additional PSS Design for Grid-Forming Converters Tied to Stiff Grid

With integration of a large number of power electronic devices into the grid, stability issues are continuously occurring. In this paper, a design method for an additional stabilizer specifically for the instability issues caused by grid-forming converters under stiff grid conditions is proposed. Firstly, a detailed model and a simplified model of the grid-forming converter tied system are established. Borrowing the phase compensation method of power system stabilizer (PSS) for synchronous machines, an additional stabilizer for grid-forming converters is designed. The impact of introduction of additional stabilizer and the variation of parameters on the critical short-circuit ratio (CSCR) of grid-forming converters are analyzed. Finally, the above analysis is verified in Matlab/Simulink. The results show that the proposed design method for the additional stabilizer can effectively increase the CSCR of the grid-forming converter tied system, and enhance the static synchronous stability under stiff grid conditions.