基于纵向阻抗的混合双极直流输电线路保护新原理

由于传统高压直流输电和柔性直流输电有各自的优缺点,为了充分发挥二者的优势,混合直流输电成为研究的热点。对由传统高压直流输电和柔性直流输电构成的混合双极直流输电线路的保护原理开展了研究,将阻抗的概念进行扩展延伸,提出了一种基于整流侧和逆变侧纵向阻抗的故障保护原理,利用PSCAD搭建仿真模型,利用MATLAB进行算法的仿真验证,该纵向阻抗是整流侧和逆变侧两端电压故障分量的差与电流故障分量的和的比值,利用纵向阻抗的幅值来区分区内外故障。区内故障时,纵向阻抗的幅值小于该极线路全长总阻抗;区外故障时,纵向阻抗的幅值大于该极线路全长总阻抗。该保护可以自行实现故障选极,故障极的纵向阻抗幅值小于整定值,非故障极的纵向阻抗幅值大于整定值。大量的仿真结果验证了所提保护原理的正确性,并可以实现故障选极。

New Principle of Hybrid Bipolar DC Transmission Line Protection Based on Longitudinal Impedance

Because traditional HVDC transmission and flexible HVDC transmission have their own advantages and disadvantages, in order to give full play to their advantages, hybrid HVDC transmission has become a research hotspot. In this paper, the protection principle of hybrid bipolar DC transmission lines consisting of traditional HVDC transmission and flexible HVDC transmission is studied. The concept of impedance is extended, and a fault protection principle based on the longitudinal impedance of the rectifier side and the inverter side is proposed. The longitudinal impedance is the ratio of the difference between the transient voltage across the rectifier side and the inverter side and the sum of the transient currents. The amplitude of longitudinal impedance is used to distinguish the internal and external faults. The amplitude of the longitudinal impedance is less than the setting value when the fault is internal fault; the amplitude of the longitudinal impedance is greater than the setting value when the fault is external fault. This protection can self-actualize the fault selection pole, the amplitude of longitudinal impedance of the fault pole is less than the setting value, and the amplitude of longitudinal impedance of the non-fault pole is greater than the setting value. Finally, simulation modeling is put up with PSCAD, protection algorithm is carried out with MATLAB, a large number of simulation results verify the correctness of the proposed protection principle, and can achieve fault pole selection.