高压直流输电系统换相失败的判断标准

建立了4条交、直流输电线路并联的多馈入高压直流输电系统(HVDC)模型并对该模型的直流输电线的换相失败现象进行了详细的理论分析和仿真研究,基于电路基本理论知识,以两端HVDC系统的关断角表达式,推导出了多馈入交、直流并联的HVDC系统的关断角表达式。通过理论分析可知,逆变侧换相失败的判断是由多种变量因素共同决定的,不能简单地假设一个或多个变量不变,而去讨论引起换相失败的结论;否则不会得到准确的结论。提出换相失败的判断标准应该为:换流阀关断角是否小于阀去游离时间对应的最小角度。若是,则会发生换相失败;若不是,则不会发生换相失败。

Criteria for Commutation Failure in HVDC Transmission System

A multi-infeed HVDC power transmission model consisting of four AC/DC transmission lines operated in parallel is set up, and detailed theoretical analysis and simulation on commutation failure of DC transmission lines in this model are conducted. According to fundamental theory of electric circuit and based on the expression of extinction angle for HVDC system at both terminal, the expression of extinction angle for HVDC system in multi-infeed AC/DC power transmission lines operated in parallel is deduced. Theoretical analysis shows that the commutation failure of iverters is caused by various variable factors, and it is not appropriate to judge the commutation failure under the assumption that one or more variables are unchangeable, otherwise, correct conclusion cannot be obtained. The authors indicate that the creteria to judge the commutation failure should be that whether the extinction angle of valve is less than the least angle corresponding to deionization time of the valve, if so, the commutation failure occurs; if not so, the commutation failure does not occur.