Submodule faults and arm parameter perturbations can cause modular multilevel converters (MMCs) to operate under asymmetric conditions
thereby affecting system stability. Traditional vector control methods suffer from a limited stability region. To address this
a passive consensus-based fault-tolerant control method suitable for asymmetric arm conditions is proposed. Firstly
in the AC subsystem
the expected trajectories for the fundamental and double-frequency circulating current components are derived by analyzing the mapping relationship between arm energy differences and AC components of the circulating current. Secondly
in the DC subsystem
the expected trajectory for the DC component of the circulating current is obtained by analyzing the mapping between inter-phase energy differences and the DC current. Finally
the consensus tracking errors of state variables between adjacent phases are incorporated into the passivity-based controller to achieve rapid and synchronized tracking of the MMC's expected state variable trajectories
ensuring the global asymptotic stability of the closed-loop system. Experimental results show that even under conditions of a 25% submodule fault in a single MMC arm and arm parameter perturbations
the proposed method can still maintain symmetrical grid-connected currents and balanced horizontal and vertical energy distribution across phases. This research can serve as a reference for the optimal design of MMCs.
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