<p>Modular multilevel converters (MMCs) are widely recognized for their use in flexible DC transmission and medium-voltage motor drive applications due to their rapid dynamic response, minimal output harmonic content, and flexible control. However, due to the complexity of operating conditions, most faults cause MMCs to operate in an unbalanced state, resulting in distorted output waveforms and system instability. This paper analyzes the operational characteristics of MMCs under unbalanced conditions and the mechanism of power fluctuations caused by this imbalance. To address the safety operation of MMCs and reduce the power fluctuations caused by unbalanced operating conditions, a comprehensive control strategy is proposed. on the basis of traditional control methods. This strategy introduces inter-phase energy balance control using the average energy accumulated in the arm as a reference value, and combines it with arm voltage balancing control, effectively suppressing power fluctuations in the MMC. Simulation and experimental results indicate that the control strategy can achieve safe MMC operation under asymmetric conditions.</p>