Inter-cluster voltage balancing control of a delta connected modular multilevel cascaded converter under unbalanced grid voltage

Protection and Control of Modern Power Systems

Huang Han¹  Ayodele B. Esan²  Oghenewvogaga J. K. Oghorada²  Mingxuan Mao³  Li Zhang⁴ 

[1] College of Engineering, Swansea University, Swansea, UK;SDG-7, Affordable and Clean Energy Research Group, Landmark University, Omu-Aran, Nigeria;Department of Electrical and Information Engineering, Landmark University, Omu-Aran, Nigeria;School of Electrical Engineering, Chongqing University, Chongqing, China;School of Electronic and Electrical Engineering, University of Leeds, Leeds, UK;

关键词: Low voltage ride through (LVRT);    Single delta bridge converter (SDBC);    Static synchronous compensator (STATCOM);    Quantification factor;   

DOI  :  10.1186/s41601-021-00203-0

来源: Springer

【 摘 要 】

A new inter-cluster DC capacitor voltage balancing scheme for a delta connected modular multilevel cascaded converter (MMCC)-based static synchronous compensator (STATCOM) is presented. A detailed power flow analysis of applying negative sequence current (NSC) and zero-sequence current (ZSC) injection methods in addressing the issue of inter-cluster DC voltage imbalance under unbalance grid voltage is carried out. A control scheme is proposed which integrates both inter-cluster methods using a quantification factor QF. This is used to achieve the sharing of the inter-cluster active power between the NSC and ZSC injection methods. An accurate method of determining the quantification factor is also presented. The proposed method offers better sub-module DC capacitor voltage balancing and prevents converter overcurrent. The influence of unbalanced grid voltage on the delta connected MMCC-based STATCOM rating using this integrated cluster balancing technique is investigated. The control scheme is verified with a 5 kV 1.2MVA MMCC-STATCOM using 3-level bridge sub-modules, and the results show the advantages of the proposed method over other inter-cluster methods.

【 授权许可】

CC BY