Practical stability‑oriented parameter co‑design method for outer and inner loops of grid‑forming converters

Haoqing Cai; Min Chen; Yiran Chen; Changsheng Hu

Practical stability‑oriented parameter co‑design method for outer and inner loops of grid‑forming converters

Vol. 25, No. 12, pp. 2321-2337, Dec. 2025

10.1007/s43236-025-01045-x

GFM converters

Sub-synchronous resonance

LC resonance

Parameter co-design method

Small-signal model

Abstract

Grid-forming (GFM) control is emerging as a promising solution for controlling grid-connected converters when the grid is composed of a high penetration level of renewable energy. Unfortunately, wideband oscillations including synchronous resonance (SR), sub-synchronous resonance (SSR), and LC resonance are found in GFM converters, which can damage the stability of the power system. Although the above resonances have been analyzed in a number of articles, the influence of the inner dual-loop, which also provides damping effect, is often ignored for the sake of simplicity. Moreover, the outer and inner loop parameter co-design method to suppress different types of resonance simultaneously is seldom discussed. To tackle these issues, this paper proposes a practical stability-oriented parameter co-design method for the outer and inner loops of GFM converters to facilitate the design procedure based on the small-signal models of the current loop, voltage loop, and power loop. The proposed method optimizes the inner dual-loop parameters by selecting values close to the maximum that can maintain high-frequency stability to reduce the interaction with the power loop, decreasing the negative damping effect for the SSR. With the optimized inner loop parameters, the outer power loop parameters can be designed according to the sub-synchronous stability. Furthermore, a gain-margin-based sensitivity analysis and a discussion of different parameter tunings are investigated. A 50-kVA prototype is built, and experimental results are presented to verify the effectiveness of the theoretical analysis and the proposed parameter co-design method.

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Cite this article

[IEEE Style]

H. Cai, M. Chen, Y. Chen, C. Hu, "Practical stability‑oriented parameter co‑design method for outer and inner loops of grid‑forming converters," Journal of Power Electronics, vol. 25, no. 12, pp. 2321-2337, 2025. DOI: 10.1007/s43236-025-01045-x.

[ACM Style]

Haoqing Cai, Min Chen, Yiran Chen, and Changsheng Hu. 2025. Practical stability‑oriented parameter co‑design method for outer and inner loops of grid‑forming converters. Journal of Power Electronics, 25, 12, (2025), 2321-2337. DOI: 10.1007/s43236-025-01045-x.