Transient Performance Evaluation of Grid-forming Control for Railway Traction Converters Considering Inter-Phase Operation

To address the small-signal oscillation issue, the grid-forming (GFM) control scheme can be an alternative to the more conventional grid-following (GFL) control to regulate the single-phase four-quadrant converter (4QC) in railway traction applications. However, unlike GFL control, the GFM control scheme cannot guarantee start-up without inrush current. The situation become even more critical when take the unique interphase operation scenario of railway vehicle. This paper evaluates the transient performance of GFM-controlled 4QC in the inter-phase operation scenario. A phase-lock-loop (PLL) based solution is developed for rapid pre-synchronization to eliminate the inrush current. The results indicate that with the proposal together with proper design of the frequency-regulator, the GFM-controlled 4QC can start up in a rapid and smooth manner.