电力建设2025，Vol.46Issue(4)：38-48,11.DOI:10.12204/j.issn.1000-7229.2025.04.004
城轨柔直T型三电平双向变流器环流抑制与中点电位平衡
Circulating Current Suppression and Midpoint Potential Balance of Flexible DC T-Type Three-Level Bidirectional Converter for Urban Rail Transit
摘要
Abstract
[Objective]A bidirectional converter integrates traction,feedback,and reactive power compensation and is the primary choice for upgrading the main equipment of an urban rail DC traction power supply system.In the field of low-voltage DC traction power supply,converters have the characteristics of low voltage and high current.The T-type three-level multi-unit parallel connection combined with carrier phase-shifting technology can meet the special requirements of low cost,low harmonic,high power density,high efficiency,and wide DC voltage operation range of urban rail DC traction power supply systems for the main equipment.However,this approach has problems such as excessive zero-sequence circulating currents and unbalanced midpoint potentials.[Methods]First,a zero-sequence circulating current model is established to address the circulating current problem in bidirectional converters.The circulating current is classified and analyzed,and a transformer low-voltage winding splitting,shared neutral line,L-shaped filter,and software control algorithm are proposed to suppress the zero-sequence circulating current.Second,in response to the problem of midpoint potential imbalance and based on the implementation of the equivalent space vector pulse width modulation,the relation of the midpoint potential to the phase voltage,phase current polarity,and space vector type is established by analyzing the T-shaped three-level single-phase topology structure.Accordingly,a feedback-compensation-based midpoint potential balance control method is proposed.[Results]Based on PSCAD/EMTDC simulation testing,it was found that various zero-sequence circulating currents could be effectively suppressed,achieving a midpoint potential balance in three-level converters during four-quadrant operation.[Conclusions]The proposed circulating current suppression method can not only suppress various zero sequence circulating currents,but also help reduce the cost of measuring the midpoint potential of three-level systems.The proposed midpoint potential control method does not require complex space vector modulation processes,has low computational complexity,is easy to implement,and can effectively control the midpoint potential.关键词
柔性直流/T型三电平/双向变流器/环流抑制/中点电位平衡Key words
flexible DC/T-type three-level/bidirectional converter/circulation suppression/midpoint potential balance分类
动力与电气工程引用本文复制引用
刘建华,李东东,李豪..城轨柔直T型三电平双向变流器环流抑制与中点电位平衡[J].电力建设,2025,46(4):38-48,11.基金项目
国家自然科学基金项目(51907116) This work is supported by the National Natural Science Foundation of China(No.51907116). （51907116）
