25kV AC Railway Catenary Power Supply Based on Virtual Synchronous Machines

This paper presents an innovative control strategy for traction power systems (TPS) in 25 kV AC electrified railways. A significant challenge in single-phase AC railway systems is the imbalance introduced into the three-phase supply grid, an issue which is absent in DC systems. To overcome this problem, a novel grid-forming control approach is proposed, enabling the synthesis of a stable single-phase AC catenary from a DC source using static power converters. The solution employs multiple grid-forming DC/AC converters operating in parallel, each one controlled by power control loops based on a modified Virtual Synchronous Machine (VSM) concept tailored for single-phase applications. This architecture ensures scalable operation and inherently shares the load without requiring centralized control or communication. All converters contribute to voltage and frequency regulation, enhancing the system robustness. The effectiveness of the proposed strategy has been validated through Hardware-In-the-Loop (HIL) testing, confirming its practical feasibility and performance.