Transactions of China Electrotechnical Society  2016, Vol. 31 Issue (9): 120-128    DOI:
Current Issue| Next Issue| Archive| Adv Search |
A Circulating Current Suppressing Method for Modular Multilevel Converter Under Unbalanced Grid Voltage
Liang Yingyu1, Zhang Tao2, Liu Jianzheng3, Yang Qixun1, Liu Shu2
1.State Key Laboratory for Alternate Electrical Power System With Renewable Energy Sources North China Electric Power University Beijing 102206 China
2.Beijing Sifang Automation Co.Ltd Beijing 100085 China
3.State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China

Download: PDF (2807 KB)   HTML (1 KB) 
Export: BibTeX | EndNote (RIS)      
Abstract  The circulating current within modular multilevel converters increases the peak/RMS value of the arm currents and the magnitude of the sub-module voltage fluctuation,and thus affects the safe operation of power electronic devices.Therefore,it is necessary to eliminate the circulating current.It is pointed that,under the unbalanced grid voltage,the second three-phase harmonic circulating current can be decomposed into positive,negative and,zero sequence components and the dc component of the three-phase circulating current is not necessary equal to each other by deriving and analyzing the phase unit instantaneous energy.The formulas of the dc component of the circulating current,i.e.the circulating current reference,are derived and a novel circulating current suppressing method,which is based on proportional-integral (PI) regulator and vector proportional-integral (VPI) regulator in parallel,is proposed.The tuning principle of the related control parameters is given.The novel circulating current suppressing method can be executed in the abc stationary reference frame so that coordinate transformation is not needed and thus it has a simple control structure.Besides that,the positive,negative,and zero sequence components of the second harmonic circulating current can be eliminated simultaneously and the method can achieve good control performance under balanced and unbalanced grid voltages.A 21-level MMC simulation model is set up in the PSCAD/EMTDC in order to validate the correctness and effectiveness of the proposed method.
Key wordsCirculating current suppression      unbalanced grid voltage      vector proportional-integral      modular multilevel converter     
Received: 19 March 2015      Published: 07 July 2016
PACS: TM721.1  
Service
E-mail this article
Add to my bookshelf
Add to citation manager
E-mail Alert
RSS
Articles by authors
Liang Yingyu
Zhang Tao
Liu Jianzheng
Yang Qixun
Liu Shu
Cite this article:   
Liang Yingyu,Zhang Tao,Liu Jianzheng等. A Circulating Current Suppressing Method for Modular Multilevel Converter Under Unbalanced Grid Voltage[J]. Transactions of China Electrotechnical Society, 2016, 31(9): 120-128.
URL:  
https://dgjsxb.ces-transaction.com/EN/     OR     https://dgjsxb.ces-transaction.com/EN/Y2016/V31/I9/120
Copyright © Transactions of China Electrotechnical Society
Supported by: Beijing Magtech