Modular Multilevel Converter Control Strategy Based on Arm Current Control Under Unbalanced Grid Condition

On-line fault diagnosis and fault-tolerant operation of modular multilevel converters — A comprehensive review

“…In [67], a feedback/feed-forward control strategy is proposed to improve the voltage balancing of MMCs under unbalanced grid conditions, which improves the disturbance rejection capability against asymmetrical faults such as SLG faults. Additionally, a control strategy combining the multi-hierarchy control with the arm current control for MMCs under SLG fault is proposed in [68]. Regarding the implementation of this multi-hierarchy control method, the symmetrical ac-side current references and the unevenly distributed dc current references in three legs can be obtained by three voltage controllers in the abc coordinate, avoiding coordinate transformation and using numerous filters in the existing methods.…”

Operation and control of MMC station with constraints of internal variables under unbalanced grid conditions

“…Therefore, it is practically significant to investigate the operation and control of MMC under UGC. The controller based on asymmetrical components, which includes the positive sequence (PS), NS and zero-sequence (ZS) parts, has been widely adopted to aggravate the power fluctuation of dc side [12][13][14][15]. Milicua et al [16] propose the power reference limitation control for ac limit, output ac voltage limit and dc bus voltage limit under UGC.…”

Modular multilevel DC–DC converter with arm interchange concept

“…The bipolar arm currents allow charging and discharging of arm capacitors, which guarantees operating with balanced capacitor voltages. The resultant peak‐to‐peak capacitor voltage ripple increases with the increase of current magnitude and/or decrease of output frequency [6, 7], i.e. in low‐frequency applications, bulky SMs capacitors should be employed to provide acceptable capacitor voltage ripple magnitude.…”