Parameter adjustment method for hybrid parallel grid-connected system with grid-following and grid-forming inverters

To facilitate the integration of high proportions of renewable energy sources into the grid, it is necessary to adopt grid-following (GFL) and grid-forming (GFM) inverters. Composed of the GFL and the GFM, the hybrid parallel grid-connected system (HPGCS) may cause the stability concern due to their disparity in output characteristics. In this paper, based on the impedance model, the grid-connection stability of the HPGCS is analyzed. It is found that the power allocation of inverters and the power demands of the grid significantly influence the stability of the HPGCS. Based on the ratio of stable operating region and the quantified analysis of the impact of the control parameters on the stability of the HPGCS, a parameter adjustment method is proposed, which ensures the stability of the HPGCS across a wide range of operating conditions. Finally, the effectiveness of the proposed method is validated through experiment results.