向无源网络供电的VSC-HVDC在送端交流电网故障下，由于送端网侧电压跌落，在限流器的作用下，会使受端交流电网出现功率缺额问题，进而影响受端电网的稳定性。为此，本项目拟通过揭示有功功率不平衡量影响直流电压变化的机理，探寻扰动下直流电压变化与频率响应之间的映射关系，建立受端电网频率的产生机制，从而实现将功率不平衡信息通过频率变化传递给保护装置的同时，利用负荷频率特性调节有功需求，提高系统的低电压穿越能力。另一方面，电网故障会产生电压负序和零序分量，并激发换流变压器注入更大的低次谐波，且VSC-HVDC的交流阻抗在低频段大部分呈容性使得系统易发生谐振，导致换流站热过载问题凸显。为此，本项目拟提出等效增大输出电抗支路非基波正序电阻的控制方法，通过全面扼制换流站输出电抗支路的非基波正序电流，提高系统故障下运行的安全性。本项目有望提高VSC-HVDC对无源网络的供电安全性及与传统保护技术的兼容性。

For a passive network supplied by voltage source converter based high voltage direct current system(VSC-HVDC),during the grid faults, active power shortages due to current limiter affecting. Furthermore, it may cause voltage collapse in receiveing grid. The project will discribe the mechanism of active power unbalance affecting DC voltage variation and discover the mapping between DC voltage variation and dynamic frequency response under disturbances. Then the method of frequency generation, which can pass active power unbalance information to protection devices by frequency variation and also ease the active power unbalance with load frequency characteristics, will be built. The proposed method will improve the ability of low voltage ride-through. On the other hand, the grid faults excite the converter transformer to produce more low-order harmonics, thereby network resonance occurs due to capacitive AC impedance of VSC-HVDC. The project will discribe the mechaism of non fundamental positive-sequence components tranferring in VSC-HVDC. A novel method is proposed to eliminate the non fundamental positive-sequence current in output branch by enlarging the equivalent non fundamental positive-sequence resistor of output branch. The proposed method will eliminate the thermal overload and waveform distortion caused by non fundamental positive-sequence components. This project is promising to improve the safety of network supplied by VSC-HVDC and the compatibility of VSC-HVDC and traditional protection technology.