Generalized impedance model and interaction analysis for multiple grid-forming and grid-following converters

The growing use of power electronics converters in the power system leads to emerging stability issues. However, existing impedance models are insufficient for analysis of the converter-induced stability issues in the converter-congregated local area, especially faced with the hybrid integration of both grid-following (GFL) and grid-forming (GFM) converters. In this paper, a generalized impedance model in the dq frame is developed to facilitate the impedance-based analysis of any grid node with both GFL and GFM converters. With this model, closed-loop, internal and external stability performance can be accurately described and predicted. This paper shows that the internal stability of power converters has the feature of transferability. Therefore, to facilitate the internal stability analysis of multiple-input and multiple-output systems, this paper proposes a stability analysis method that utilizes the determinant of total admittance (matrices in high dimension) for direct stability demonstration, based on the recognition of instability pattern. Finally, the procedure for integrating power converters is considered to help with the stability-oriented design. The established impedance model, the proposed stability analysis method and the converter integration procedure are validated with control hardware-in-the-loop results in a study case of a multi-terminal network with current-controlled converters and virtual synchronous generators.

Automated summary

This paper investigates the stability issues of power electronics converters in the power system and proposes an impedance-based analysis method. By developing a generalized impedance model in the dq frame, the stability performance of grid nodes with both grid-following and grid-forming converters can be accurately described and predicted. Additionally, a stability analysis method and converter integration procedure are proposed to facilitate stability-oriented design.