模块化多电平柔性直流输电是发展新一代能源电力系统的重要组成部分，其交流侧发生故障易引起新能源发电系统脱网运行和用户侧切负荷，甚至导致互联大电网之间解列。针对现有柔性直流输电交流侧故障穿越方法存在多目标控制困难的问题，本项目基于故障能量与换流器内在能量的最优分布控制，开展柔性直流输电交流侧故障安全快速穿越研究，主要内容为：基于广义S变换理论分析交直流侧故障和能量交互特征，刻画不同故障下各电气参数随能量差异变化的规律，揭示故障能量与换流器内在能量流动机理;通过控制各桥臂电流分量主动调节故障能量及换流器内各桥臂能量的分布，优化多因素约束下的输出功率运行区间;结合先进控制理论，提出在能量最优分布下主动应对交流侧故障的快速穿越调控方法。本项目研究成果为快速应用阶段的柔性直流输电安全稳定运行提供新思路与理论支撑。

MMC-HVDC (High-voltage Direct Current Based on Modular Multilevel Converter) is an important part of the new power system. Failure on AC side is likely to cause the off-grid operation of the renewable energy system and the cut-off operation on the load side, and can even lead to the disconnection among the interconnected power grids. Since it is difficult for the existing fault ride-through control of the MMC-HVDC system to achieve multiple target control, the proposed project is to optimize control between the energy of fault and the optimal distribution control of the intrinsic energy of the converter,and to achieve the goal of fast fault ride-through control. According to the generalized S-transformation theory, the AC-DC fault and the characteristics of energy interaction are analyzed. The electrical parameters vary in different faults conditions. Therefore, the mechanism how energy of fault and the intrinsic energy in the inverter flows is revealed. To adjust the energy of fault and the energy distribution of each arm in the converter, current components of each arm are controlled and the output power operating region under multi-factor constraints is optimized. Meanwhile, combined with the advanced control theory, a fault ride-through control method is proposed to actively respond to the AC side fault under the optimal energy distribution. This project provides new ideas and theoretical support for the safe and stable operation of MMC-HVDC system.