谐波阻抗在直流滤波器保护中的应用

直流滤波器是高压直流输电系统不可或缺的设备。目前直流滤波器保护都采用单一的电流量保护，并且大都利用调谐频次电流作为保护量。当滤波器靠近首端接地故障时，滤波器调谐频率发生较大偏移，调谐频次电流减小，使得滤波器差动保护差流较小，灵敏度不足，保护可能出现拒动。提出了滤波器谐波阻抗保护，保护同时接入电压和电流作为保护量，计算滤波器较小调谐频次的谐波阻抗大小作为保护判据，滤波器靠近首端接地故障时保护灵敏度高，并可以反应多种故障，也可作为滤波器失谐监视判据。通过PSCAD仿真验证了该判据的可行性和可靠性，这将对直流滤波器进行更加完善可靠的保护。

Application of harmonic impedance in the DC filter protection

The DC filter is an indispensable equipment in the HVDC transmission system. At present, DC filter protections only use the current protection, and most of which use the tuning frequency current. When the earth fault is close to the head end of filter, there is a greater shift of tuning frequency, and the harmonic current is reduced, so the differential current of filter is reduced, and the protection is lack of sensitivity, and the protection may not operate. In this paper, the harmonic impedance protection is proposed, and the protection makes use of voltage and current, and uses smaller tuning frequency harmonic impedance magnitude as the protection criterion. When the earth fault is close to the head end of filter, the protection with high sensitivity can respond many kinds of faults, but also as a filter detuning monitoring criterion. The simulation using PSCAD verifies the feasibility and reliability of protection, and the harmonic impedance protection will protect the DC filter more reliably.