Control of Grid-Forming VSCs: A Perspective of Adaptive Fast/Slow Internal Voltage Source

TL;DR

This paper proposes an adaptive control strategy for grid-forming VSCs that dynamically switches between fast and slow internal voltage source dynamics to enhance stability and service capability during grid disturbances.

Contribution

It introduces a novel adaptive control method for GFM-VSCs that balances fast and slow IVS dynamics based on system needs, improving stability and robustness.

Findings

Enhances transient stability of GFM-VSCs during disturbances.

Robust across different grid strengths and disturbance types.

Experimental results confirm theoretical advantages.

Abstract

Grid-forming (GFM) capability requirements are increasingly imposed on grid-connected voltage-source converters (VSCs). Under large grid disturbances, GFM-VSCs need to remain stable while providing GFM services. Yet, such objectives, as pointed out in this paper, inherently lead to conflicting requirements on the dynamics of internal voltage source (IVS) of GFM-VSCs, i.e., the fast IVS dynamics is needed to avoid the loss of synchronism with the grid, whereas the slow IVS dynamics is preferred for maintaining GFM capability. To tackle this challenge, an adaptive fast/slow IVS control is proposed, which switches GFM-VSC between fast and slow IVS dynamics based on system needs. The proposed method enhances the transient stability of GFM-VSC, whilst maximizing its capability of providing GFM service. Further, the approach is robust to different grid strengths and different types of grid disturbances. The experimental results verify the theoretical findings and the effectiveness of the proposed control method.