Optimized configuration grid-following/grid-forming units for stability improvement in renewable plants

With the extensive access of new energy generation equipment, the dynamic characteristics of the power system have changed significantly, which can easily lead to phenomena such as sub-synchronous or super-synchronous oscillations. The grid-forming converters can effectively support the frequency and voltage of the power grid, and equipping a certain amount of grid-forming converters can effectively improve the stability of the system, but it is difficult to quantitatively calculate the ratio of grid-forming converters. In this paper, we firstly establish a mixed multi-feeder system model with grid-following converters and grid-following converters, and analyze the equivalent external characteristic model of grid-forming converters. We use the generalized short-circuit ratio and the critical generalized short-circuit ratio to evaluate the system stability, and analyze the relationship between the generalized short-circuit ratio and the grid-forming converters ratios, and put forward an optimal allocation method based on the grid-forming capacity ratios to enhance the stability of new energy field stations. Finally, the effectiveness of the proposed method is verified through simulation. It can significantly improve the stability of the station.