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FU Hua,YU Xiang.Capacitor Voltage Balancing Model for Modular Multilevel Converter Using Shell Sorting Algorithm and Bias Control[J].JOURNAL OF POWER SUPPLY,2018,16(5):38-44
Capacitor Voltage Balancing Model for Modular Multilevel Converter Using Shell Sorting Algorithm and Bias Control
Received:July 28, 2016  Revised:February 19, 2018
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DOI:10.13234/j.issn.2095-2805.2018.5.38
Keywords:modular multilevel converter  voltage balancing control  deviation control  Shell sorting algorithm  switching efficiency
Fund Project:The National Natural Science Foundation of China (General Program, Key Program, Major Research Plan)
     
AuthorInstitutionEmail
FU Hua Faulty of Electrical and Control Engineering, Liaoning Technical University, Huludao , China
YU Xiang Faulty of Electrical and Control Engineering, Liaoning Technical University, Huludao , China 2511430686@qq.com
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Abstract:
      The voltage balancing problem of sub-modules(SMs) in a modular multilevel converter(MMC) is the key to the stable operation of high voltage direct current(HVDC) transmission system. However, when the number of SMs is ex-cessive, the voltage balancing model based on the traditional sorting algorithm will lead to a large amount of computation load when sorting the capacitor voltages and thus occupies numerous resources, which poses a challenge to the design of hardware. To this end, an improved capacitor voltage balancing model for MMC is designed based on Shell sorting algorithm and bias control. To determine whether to recalculate the trigger pulse or not, the numbers of on-state SMs in the previous and present control cycles are compared, together with the detection of deviation between capacitor voltages of SMs and their average value. In addition, the value of deviation determines whether the SMs should be put into operation or not. The Shell sorting algorithm is used to sort the SMs that satisfy the corresponding decision criteria when the bridge arm is in different states, and the SMs are input according to the sequence after arrangement, thus ensuring the efficient and reliable operation of the system. An MMC model was set up in PSCAD/EMTDC, and the validity of the voltage balancing control model for SMs was verified. Simulation results showed that this control model can effectively realize the balancing control of capacitor voltage of SMs at a low frequency.
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