多落点直流输电系统换相失败影响因素的仿真分析

Simulative Analysis on Factors Impacting Commutation Failure in Multi-Terminal HVDC Transmission System

在多落点高压直流输电系统中,影响换相失败的因素非常复杂。在引出送端多落点概念并建立送端和受端多落点经典模型的基础上,针对耦合导纳、交流系统强度、故障位置这3个方面对系统逆变侧发生换相失败的影响进行了仿真分析。结果表明:交直流并联的受端多落点系统存在强、弱临界耦合导纳2个指标,送端多落点存在弱临界耦合导纳,但故障后2系统难以实现同调恢复;非耦合侧系统强度也会影响系统的换相失败,系统强度越大,抵抗换相失败的能力越强,耦合侧系统强度对换相失败的影响更大;不同故障位置和不同耦合侧对换相失败的影响不同。

In multi-terminal HVDC transmission system the factors impacting commutation failure are complicated. On the basis of drawing the concept of multi-terminals at sending end and building classical models for sending end with multi-infeed terminals and receiving end with multi-receiving terminals, the influences of coupling admittance, strength of AC system and fault-position on commutation failure occurred at inverter side are analyzed by simulation. Simulation results show that as for AC/DC parallel system there are two indices of strong and weak critical coupling admittance in receiving end with multi-terminals and there is the index of weak critical coupling admittance in sending end with multi-terminals, and after the fault it is difficult to recovery the two system coherently; the system strength at non-coupled side influences commutation failure too, the stronger the system, the stronger the ability to resist commutation failure, thus the influence of system strength at coupled side on commutation failure is greater; different fault-positions and different coupled side differently impact on commutation failure.