An adaptive loss reduction control strategy for MMC with low switching frequency
For the MMC with HBSM,an adaptive loss reduction control strategy with low switching frequency is proposed to solve the problem of high switching loss of converter valve caused by the nearest level modulation(NLM)strategy and sort based capacitor voltage balancing control strategy.Firstly,the relationship between the capacitor voltage balancing effect and the switching frequency is analyzed,and the requirements for capacitor volt-age balancing in practical engineering applications are clarified,providing a theoretical basis for the subsequent a-daptive loss reduction control strategy with low switching frequency.Secondly,based on the dynamic limit values of the capacitor voltage,the direction of the arm current and the switching status of the submodules in the previous control cycle,the priority of submodule in the current control cycle is determined.The unnecessary extra switching actions of the submodules are reduced.Then,the linear interpolation method is used to realize the adaptive adjust-ment of the dynamic limit value of the capacitor voltage under different system transmission power,which further re-duces the switching frequency of the submodules.Finally,the MMC-HVDC electromagnetic transient simulation model with 200 submodules is built in MATLAB/Simulink to verify the proposed loss reduction control strategy.
flexible DC transmission technologymodular multi-level convertervoltage balancing control strate-gylow switching frequency loss reduction control
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