多馈入直流输电系统换相失败机制及特性

随着多直流接入受端交流系统的规模不断增大,运行人员对多回直流换相失败以及闭锁的关注度日益提升。文中建立了多馈入直流输电系统模型,从换相失败发生的本质出发,分析多种因素对换相失败发生概率的影响。从机制上研究换相失败对交流系统和直流系统的影响,并与直流闭锁对系统的影响进行对比分析。通过对多馈入直流输电系统的机电暂态仿真,验证由交流系统引起的多回直流换相失败与直流闭锁的差异。综合理论和仿真研究可知,在交流系统故障及时清除的情况下,多回直流换相失败并不会导致多回直流同时闭锁,不会对系统造成大的影响。而直流闭锁故障,在不采取控制措施的情况下,会造成系统功率不平衡,严重时导致系统失步,影响系统安全稳定运行。

Research and Electromechanical Transient Simulation on Mechanism of Commutation Failure in Multi-Infeed HVDC Power Transmission System

Along with increasing extension of the scale of AC power system located at receiving end of multi-infeed HVDC power transmission system,more and more attentions are paid to the commutation failure occurred in multi-circuit HVDC transmission systems.A multi-infeed HVDC power transmission system model was built,and from the essence of commutation failure the influences of various factors on occurrence probability of commutation failure were analyzed.Based on the occurrence mechanism of commutation failure,the influences of commutation failure on both HVDC and HVAC power systems were researched,and comparative analysis of the influence of DC block on the two systems was performed.Through electromechanical transient simulation of multi-infeed HVDC power transmission system,the differences between multi-circuit HVDC commutation failure caused by AC power system and the HVDC block were verified.Synthesizing both results from theoretical research and simulation results,it was known that when the faults occurred in AC system were cleared away in tine,the commutation failure in multi-circuit HVDC power transmission system would not cause simultaneous DC block in multi-circuit HVDC power transmission system and not lead to obvious impact on the whole system.However the DC block would cause power imbalance in the whole system while control measures were not adopted,and even the system would be out of synchronization or splitted when the power imbalance was severe,thus the secure and stable operation of the whole system would be affected.