交流系统扰动时有发生，扰动时直流配电网中送端换流器吸收的有功功率具有快速自恢复特性，这一特性易引起交流母线电压失稳。为此，本项目拟建立扰动下送端换流器的自恢复模型，然后考虑送端换流器无功功率特性建立其交流侧的系统模型，求取不同电网等值电抗时交流网络的PV曲线鞍结点，进而探寻扰动下变流器类负荷自恢复特性引起交流母线电压失稳的机理。在此基础上，设计扰动观测器定位交流母线电压波动的扰动源，并提出基于部分模型匹配算法的扰动补偿方法，通过控制负荷的恢复速率提高交流母线电压的暂态稳定性。扰动后，交流电网可能变弱，考虑直流配电网静态电压质量要求，建立下垂系数与负荷的静态特性曲线的映射关系，提出下垂系数跟随电网强度自适应调整策略，将部分有功潮流转移到其他送端换流器，以提高交流母线电压的静态稳定裕度。本项目将送端换流器控制为柔性负荷，有望提高交直流电网运行的电压稳定性。

AC system disturbances occur from time to time, and the active power absorbed by the sending-terminal converter of the DC distribution network has the characteristics of fast self-recovery, which easily causes the voltage instability of the AC bus. For this reason, this project intends to establish the self-recovery model of the sending-terminal converter under disturbance, and then establish the system model of the AC side of the sending-terminal converter, to find the PV curve saddle node of the AC network under different equivalent impedance of the power grid, and to explore the mechanism of voltage instability of the AC bus caused by the self-recovery characteristics. On this basis, considering the transient power quality of DC distribution grid, the time constant of the station-level control of the sending-terminal converter is optimized, and the transient stability of AC bus voltage is improved by controlling the recovery rate of loads. After disturbance, AC power grid may become weaker. Considering the requirement of static voltage quality of DC distribution grid, this project intends to establish the mapping relationship between coefficients of droop control and static characteristic curve of load, design the principle of adaptive adjustment of coefficient of droop control with power network strength, and construct the sending-terminal converters as loads sensitive to AC voltage, and transfer part of active power flow to other converters in order to improve the static stability margin of AC bus voltage when the power network is weak. In this project, the sending-terminal converter is controlled as a flexible load, which is expected to improve the voltage stability of distribution network.