| Citation:Oghenewvogaga J. K. Oghorada,Li Zhang,Huang Han,Ayodele B. Esan,Mingxuan Mao.Inter-cluster voltage balancing control of a delta connected modular multilevel cascaded converter under unbalanced grid voltage[J].Protection and Control of Modern Power Systems,2021,V6(3):289-299[Copy] |
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| Abstract: |
| 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. |
| Key words: Low voltage ride through (LVRT),
Single delta bridge converter (SDBC),
Static synchronous compensator (STATCOM),
Quantification factor, |
| DOI：10.1186/s41601-021-00203-0 |
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