A Novel Advanced Traction Power Supply System Based on Modular Multilevel Converter

Abstract

Due to the attractive advantages such as modularity, scalability and excellent power quality of modular multilevel converter (MMC), converters based on MMC could be a promising alternative solution for traction transformer. A novel MMC-based advanced co-phase traction power supply system is proposed in this paper to solve power quality issues and eliminate the neutral sections in the traditional traction power supply system. And in the proposed system, a DC power transmission system is designed, which provides convenient access for distributed energies benefiting the utilization of the natural resources such as solar energy and wind energy along railways. In order to ensure the normal operation of the proposed system, nearest-level modulation considering voltage balancing is designed for MMCs. The mathematic model three-phase MMC-based rectifier is derived in detail. Based on the mathematic model, dual current-loop control is designed for the rectifier. Besides, the parallel operating traction substations suffer circulating current issue. A droop control combining with double closed-loop control is designed to deal with the problem. The correctness and feasibility of the system and its modulation and control strategies is verified through simulation and a small-scale experiment. INDEX TERMS Electrified railway, traction power supply system, modular multilevel converter (MMC), three-phase rectifier, single-phase inverter.

Novel double‐layer DC/AC railway traction power supply system with renewable integration

“…It can be seen that power increment is proportional to voltage increment. In order to achieve a rational energy flow, the reference voltage of a parallel converter can be obtained by (4). The relationship between the reference voltage and the feedback power is shown in Fig.…”

“…Different sections are supplied by different phases of the power grid, resulting in inconsistent voltage phase between adjacent sections. Therefore, neutral sections are essential, yet the electrical dead zone in neutral sections will inevitably bring speed loss, electric shock, and other adverse effects [4]. (ii) Power quality in the grid side.…”

“…In [10], a novel back‐to‐back topology based on multiple converters is proposed and applied in TPSS, it can meet the high power demand of the traction system. A novel TPSS based on modular multilevel converters (MMC) is proposed in [4], both the mathematical model and control strategy of the MMC converter are presented. The above researches mainly focus on the modelling and control of a single power electronic converter.…”

“…There is a lack of system‐level operation study on the full power electronics based TPSS. In [4], the conventional AC droop control scheme is directly applied to single‐phase inverters without the consideration of transmission line impedance. A modified droop control strategy is proposed for railway auxiliary power supply system in [11], but the topology of auxiliary system is different from the full power electronics based TPSS.…”

Control of Multilevel Converter for AC Traction Substation with Power Symmetrization Unit

“…This topology is promising industrial solution, that can be tracked in [4] and [5] (ABB and Siemens company). These solutions are industrially suitable against to the novel configurations described in papers [6] and [7]. The introduced solution have electronic balancer directly connected on secondary winding of substation transformer.…”