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Mathematical Problems in Engineering
Volume 2017 (2017), Article ID 4157165, 14 pages
Research Article

Research on Control Strategy of AC-DC-AC Substation Based on Modular Multilevel Converter

School of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China

Correspondence should be addressed to Fei Chang

Received 22 February 2017; Revised 21 August 2017; Accepted 10 September 2017; Published 8 November 2017

Academic Editor: Yakov Strelniker

Copyright © 2017 Fei Chang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Significant disadvantages in power quality especially the unbalance problem and neutral sections restrict the evolution of conventional traction power supply system. A new traction power supply system based on three-phase to single-phase converter is studied, which can transfer active power from three-phase grid to single-phase catenary. One catenary section could be utilized in the new traction power supply system instead of the multiple split sections in conventional system. Three-phase to single-phase converter is the core equipment of new traction power system. MMC (modular multilevel converter) structure of AC-DC-AC substation is proposed in this paper. To solve the problem of the capacitor voltage balancing in MMC, a parallel sorting algorithm based on field programmable gate array (FPGA) is studied. And the correctness and effectiveness of the algorithm are verified by experiments. In addition, it is inevitable that the AC grid voltage will be unbalanced caused by the fault in the new system. Therefore, this paper focuses on the analysis of the effect of the unbalanced grid voltage on the operating characteristics of the MMC system. Finally, the correctness of the theoretical analysis is verified by simulation.