基于无功功率短路比的直流闭锁暂态过电压计算方法

针对现有特高压直流闭锁引起交流系统换流母线暂态过电压计算方法在极低短路比情况下可能无实解的问题,基于直流闭锁后的谐振电路,推导建立了暂态过电压与谐振频率的关系式。参照短路比的定义,提出无功功率短路比的概念,在此基础上,提出适用范围更广的直流闭锁暂态过电压计算方法。研究发现,换流母线暂态过电压随着无功功率短路比的减小呈非线性加速上升的趋势。以DIgSILENT为平台搭建国际大电网会议(CIGRE)直流输电标准测试系统与±800 kV天中直流送端系统,仿真分析验证了所提出的暂态过电压计算方法的有效性,在极低短路比系统中仍然适用。

Calculation Method of Transient Overvoltage Due to DC Blocking Based on Short Circuit Ratio of Reactive Power

The existing calculation methods of transient overvoltage on the commutation bus due to the ultra-high voltage direct current(UHVDC)blocking have no real solution in the case of extremely low short-circuit ratio. Based on the resonant circuit after DC blocking, this paper deduces and establishes the expression of the relationship between transient overvoltage and resonant frequency. Referring to the definition of short circuit ratio, the concept of reactive power short-circuit ratio is proposed. Then, a method for calculating transient overvoltage after DC blocking is proposed with wider application range. It is found that the trend of transient overvoltage on the commutation bus is nonlinear and accelerates with the decrease of reactive power short circuit ratio. Finally, based on the DIgSILENT simulation platform, the DC transmission standard test system of International Council on Large Electric Systems and Xinjiang Tianshan-Zhongzhou DC transmission system of China are built to verify the proposed calculation method of transient overvoltage. The simulation results show that the proposed calculation method is effective and applicable in the system with extremely low short-circuit ratio.