The largest 1 Gvar STATCOM Deployment in the Korean Power System: Architecture, Control, and Operational Approach

This paper presents the deployment and operational strategies of a 1Gvar STATCOM at the

Shin-Okcheon substation—a strategic alternative to physical grid reinforcement. It has been confirmed through analytical results that the 1Gvar STATCOM effectively expands voltage stability margins, increasing the regional generation limit and alleviating annual transmission constraints.

A 2 × 500 Mvar modular architecture has been adopted for localising fault impacts and for maintenance efficiency. In addition, a Master Controller–based hierarchical control structure is implemented to coordinate unit outputs, secure droop stability, and support integrated fault responses. Through the application of 3+1 single-phase transformer units, complemented by a pre‑configured manual changeover strategy that minimises operational and maintenance risks.

Moreover, operational integrity is ensured through stringent commissioning procedures, including full‑range ±Q performance testing and a 30‑day fault‑free operation requirement, all of which are supported by a systematic supplier‑led O&M framework.

This project is regarded as a pragmatic model for global TSOs utilising large-scale STATCOM to overcome transmission bottlenecks and support stable energy transitions.