跟网构网混合系统的鲁棒稳定性分析与优化配置OA

The grid-following(GFL)converters are weakly supportive of the grid.As the proportion of synchronous machines decreases,it is necessary to configure a certain number of grid-forming(GFM)converters with the ability to actively support the grid,which will form the GFL-GFM hybrid system.The stability mechanism of this system is closely related to the grid strength characterized by the short circuit ratio(SCR).Considering that the dynamic external characteristics of renewable energy devices are difficult to model in detail,and SCR-based analysis methods have not yet been able to provide robust stability bounds.Therefore,this paper investigates the quantitative assessment method of robust stability for hybrid systems and provides a new theoretical framework for the optimal configuration of converters.Firstly,we construct a multiplicative perturbation model of the hybrid system to quantify the uncertainties in the system and deconstruct the model into two subsystems with equivalent robust stability in the low/sub-synchronous frequency bands,thus reducing the complexity of the analytical model.Secondly,we analyze the intrinsic relationship between robust stability and grid strength in multi-frequency bands,combine the modal decoupling theory and the small gain theorem to establish a sufficient criterion for robust stability,and then quantify the critical value of grid strength by determining the worst boundary conditions.Then,an optimal configuration model is proposed to minimize the number of modifications and the constraint of robust stability.Finally,simulation examples verified the effectiveness of the dynamic segmentation method and optimization configuration scheme for hybrid systems.