An energy-based multi-loops control strategy for modular multilevel converter

This paper presents an energy-based multi-loops control strategy for the modular multilevel converter, which can provide excellent dynamic performance. A method to remove the ripple components from the DC-link voltage and the arm differential voltage is introduced to achieve the DC components without using the low-pass filters. The energy-balance relationship in the MMC is analyzed and an energy-based total energy controller is proposed. In addition, the arm voltage feedforward loop is introduced to the modulator in order to improve the dynamic performance of the inner current control with the repetitive circulating current controller. Since low-pass filters and PI controllers with low bandwidth are eliminated, the proposed control scheme can achieve excellent dynamic performance. The advantages of the proposed control scheme are verified by both simulations and experiments.