小干扰下系统构网需求与设备构网能力探讨

s synchronous generators are replaced by renewable energy sources, the support strength of voltage and frequency in the power system continues to decline, increasing the risk of system instability. Grid-Forming (GFM) devices, characterized by voltage source behavior, provide support for the system voltage and frequency. However, current understanding of GFM characteristics is mostly from the device perspective, lacking research from the system perspective on what GFM is, why it is needed, and how to evaluate GFM capabilities. Moreover, the current definition of GFM is based on qualitative analysis of existing control structures, such as droop control or virtual synchronous machine control, lacking quantitative criteria to analyze potential GFM capabilities of other control structures. To address this, this paper starts from the closed-loop interaction between devices and the grid, using the concept of system strength to represent the stability and robustness of the power system. It explains the relationship between GFM capabilities and system strength, exploring the GFM requirements and evaluation methods from the perspective of system dynamic. On this basis, devices that can enhance system voltage strength/frequency strength are defined as voltage GFM/frequency GFM devices. Corresponding mathematical criteria and methods for quantitatively analyzing voltage/frequency GFM capabilities are proposed. The proposed definition and quantification methods of GFM can also achieve frequency-band-specific quantification, enabling quantitative analysis of the GFM capabilities of devices at different frequency points.