LI Hui, XIE Xiangjie, WU You, et al. Power Loss Modeling and Analysis of Hybrid MMCs with Active Redundancy for Offshore DC Wind Turbines[J]. 2021, 47(8): 2655-2668.
LI Hui, XIE Xiangjie, WU You, et al. Power Loss Modeling and Analysis of Hybrid MMCs with Active Redundancy for Offshore DC Wind Turbines[J]. 2021, 47(8): 2655-2668.DOI:
The simulation method is not applicable to rapidly assessing the power loss of hybrid modular multilevel converter(HMMC) at initial design stage
and existing analytical models mainly focus on the modular multilevel converter(MMC) constituted by submodules(SMs) with the same structure
without taking into account the impacts of active redundancy. Therefore
we proposed an analytical power loss model for HMMC with active redundancy. Firstly
both fixed level(FL) and voltage sharing(VS) redundancy modes were taken into consideration
and the modulation strategies of half-and full-bridge SMs were analyzed. Then
according to the conduction and switching states of power devices in SMs
the analytical approach to power loss of HMMC with different redundancy modes was derived. Finally
by taking a 10 MW and 10 kV MMC as an example
the efficacy of the proposed model was verified through simulations. Moreover
the influences of different redundancy modes and SM structures on power loss were analyzed and compared. The results show that
at the rated wind speed
the total loss of HMMC almost linearly increases with the increase of redundant half-bridge SMs(HBSMs) or full-bridge SMs(FBSMs). Compared with that in the FL mode
the total loss change with redundant HBSMs is slighter in the VS mode
which becomes greater with redundant FBSMs. The research can provide a theoretical basis for the loss calculation of grid-connected MMC for offshore DC wind turbine.