TY - JOUR
T1 - Inherent SM Voltage Balance for Multilevel Circulant Modulation in Modular Multilevel DC--DC Converters
AU - Fan, Shiyuan
AU - Xiang, Xin
AU - Sheng, Jing
AU - Gu, Yunjie
AU - Yang, Huan
AU - Li, Wuhua
AU - He, Xiangning
AU - Green, Timothy C
N1 - Funding Information:
This work was supported in part by the National Natural Science Foundation of China under Grants 52061635101 and 52107214, and in part by the National Natural Science Foundation for Distinguished Young Scholars under Grant 51925702.
Publisher Copyright:
© 1986-2012 IEEE.
PY - 2022/2/1
Y1 - 2022/2/1
N2 - The modularity of a modular multilevel dc converter (MMDC) makes it attractive for medium-voltage distribution systems. Inherent balance of submodule (SM) capacitor voltages is considered as an ideal property, which avoids a complex sorting process based on many measurements thereby reducing costs and enhancing reliability. This article extends the inherent balance concept previously shown for square-wave modulation to a multilevel version for MMDCs. A switching duty matrix dU is introduced: it is a circulant matrix of preset multilevel switching patterns with multiple stages and multiple durations. Inherent voltage balance is ensured with a full-rank dU. Circulant matrix theory shows that this is equivalent to a simplified common factor criterion. A nonfull rank dU causes clusters of SM voltage rather than a single common value, with the clusters indicated by the kernel of the matrix. A generalized coprime criterion is developed into several deductions that serve as practical guidance for design of multilevel circulant modulation. The theoretical development is verified through full-scale simulations and downscaled experiments. The effectiveness of the proposed circulant modulation in achieving SM voltage balance in an MMDC is demonstrated.
AB - The modularity of a modular multilevel dc converter (MMDC) makes it attractive for medium-voltage distribution systems. Inherent balance of submodule (SM) capacitor voltages is considered as an ideal property, which avoids a complex sorting process based on many measurements thereby reducing costs and enhancing reliability. This article extends the inherent balance concept previously shown for square-wave modulation to a multilevel version for MMDCs. A switching duty matrix dU is introduced: it is a circulant matrix of preset multilevel switching patterns with multiple stages and multiple durations. Inherent voltage balance is ensured with a full-rank dU. Circulant matrix theory shows that this is equivalent to a simplified common factor criterion. A nonfull rank dU causes clusters of SM voltage rather than a single common value, with the clusters indicated by the kernel of the matrix. A generalized coprime criterion is developed into several deductions that serve as practical guidance for design of multilevel circulant modulation. The theoretical development is verified through full-scale simulations and downscaled experiments. The effectiveness of the proposed circulant modulation in achieving SM voltage balance in an MMDC is demonstrated.
KW - Inherent balance
KW - modular multilevel dc converter (MMDC)
KW - multilevel circulant modulation
KW - submodule (SM) capacitor voltage
UR - http://www.scopus.com/inward/record.url?scp=85113233830&partnerID=8YFLogxK
U2 - 10.1109/TPEL.2021.3105122
DO - 10.1109/TPEL.2021.3105122
M3 - Article
VL - 37
SP - 1352
EP - 1368
JO - IEEE Transactions on Power Electronics
JF - IEEE Transactions on Power Electronics
SN - 0885-8993
IS - 2
ER -