Summary
Grid-forming (GFM) converters are essential in modern power systems, providing voltage magnitude, phase angle and frequency regulation, synthetic inertia, potential black-start capability, and stable operation without requiring phase-locked loops, which are prone to instability in weak grids. However, parallel operation of GFM converters, poses challenges due to potential control interactions. Stable performance requires precise active and reactive power control. Conventional GFM strategies typically regulate an internal voltage magnitude and phase angle behind a virtual impedance. Reactive power is controlled via the internal voltage magnitude and active power via frequency droop or virtual synchronous machine dynamics. Effective P-Q decoupling requires d-q frame alignment with terminal voltage angle. This alignment is a fast process performed by PLLs in grid-following (GFL) converters.
Read more Read lessTraditional GFM controls, relying on slower power-angle dynamics, offer much slower synchronization.
Building on an established GFM concept that integrates PLL-like synchronization without explicit
PLLs, this paper extends the approach to a ±525 kV, 2000 MW MMC VSC HVDC bipole. The strategy adopts GFL vector current control with two modifications: (i) internal angle generation via frequencydroop/power-angle controller, and (ii) outer-loop d-axis current adjustment to null q-axis terminal voltage. This yields key advantages: reduced interactions, highly damped active power response, lower fault current margins, fast transient current limiting, seamless GFL auxiliary control reuse (e.g., dynamic reactive current injection), and robustness across a wide range of system strengths without retuning.
Electromagnetic transient simulations validate controller performance under voltage magnitude (±0.05 pu) and phase angle (±30°) steps, frequency steps/ramp (±0.1 Hz instantaneous, ±1 Hz at 4 Hz/s), and 150 ms bolted faults (three-phase and single-phase) with 1.1 pu current limit in both grid-connected and islanded operation. Results exhibit fast, stable, well-damped responses.
Additional informations
| Publication type | Session Materials |
|---|---|
| Reference | C4_11856_2026 |
| Publication year | |
| Publisher | CIGRE |
| Country | Canada |
| Study committees |
|
| File size | 964 KB |
| Price for non member | 30 € |
| Price for member | 30 € |
Authors
ST.HILAIRE Riley - TransGrid Solutions, Canada; KARAWITA Chandana - TransGrid Solutions, Canada; ANNAKKAGE Udaya - University of Manitoba, Canada
Keywords
Grid Forming Converters, Terminal Angle Reference, PQ Decoupling, Robust Control, Reduced Current Margin
