Grid-Forming Controller for Multi DC/AC Converter Topology Supplying 25 kVAC Single-Phase Railway Catenary From 3 kVDC

Abstract

One of the primary challenges associated with single-phase AC railway electrification is the unbalance created within the three-phase supply grid. This problem does not arise in DC electrification systems. The aim of this article is to introduce a novel Grid-Forming control strategy, which applied to a power electronics based topology allows the generation of an AC catenary from the DC catenary. Focusing on the capabilities of the control algorithm, the system is presented as a fully scalable solution employing multiple grid-forming DC/AC converters. These converters use power control loops based on the Virtual Synchronous Machine concept, adapted to single-phase operation. A key advantage of this approach is that all converters within the system contribute to supporting both voltage and frequency stability. In addition, the implementation does not require a higher-level controller or communication system. Through an appropriate power control design, the power supplied by each converter, relative to the total load demand, can be determined.