Grid-following and Grid-forming Switching Control for Grid-connected Inverters Considering Small-signal Security Region
A novel switching algorithm prevents blackouts by dynamically managing inverter modes in real-time.
A team of researchers, led by Qiping Lai and Yi Shen, has published a pivotal paper addressing a critical gap in renewable energy infrastructure. Their work focuses on grid-connected inverters (GCIs), the essential devices that convert power from sources like solar and wind for use on the main electrical grid. In high-penetration renewable systems, these inverters must dynamically switch between two control modes: grid-following (GFL), which synchronizes to an existing grid signal, and grid-forming (GFM), which can create a stable voltage reference to support a weak or failing grid. The safe transition between these modes during highly variable grid conditions has been a largely unsolved challenge, posing a risk to grid stability.
To overcome this, the researchers established a full-order small-signal state-space model that precisely captures all internal circuit and control dynamics of the GFL-GFM switched system. They then defined and characterized the system's Small-Signal Security Region (SSSR). The core innovation is a novel Comprehensive Stability Index (CSI), which synthesizes three key factors: the stability margin, parameter sensitivity, and distance to the security boundary. This CSI enables a new multi-objective adaptive switching control strategy. Instead of a simple on/off toggle, the system can now make intelligent, real-time decisions on when and how to switch modes to maximize robustness. The proposed method and control mechanism were successfully validated through detailed electromagnetic transient (EMT) simulations, proving its effectiveness in maintaining dynamic security.
- Introduces a novel Comprehensive Stability Index (CSI) that integrates stability margin, parameter sensitivity, and boundary distance for intelligent control.
- Develops a full-order small-signal model and defines the Small-Signal Security Region (SSSR) for GFL-GFM switched inverter systems.
- Proposes and validates an adaptive multi-objective switching control strategy, proven via EMT simulation, to ensure grid robustness during renewable fluctuations.
Why It Matters
This research is crucial for building resilient, high-renewable power grids that can avoid blackouts by autonomously managing complex, real-time stability threats.