柔性直流电网单极接地短路电流计算方法

Calculation Method for Line-to-Ground Short-Circuit Currents of VSC-HVDC Grid

在柔性直流电网工程设计与直流断路器选型中,电网的短路电流是重要的参考依据。针对以架空线作为金属回线网络的真双极柔性直流电网,文章提出了一种单极接地短路电流计算方法。该方法的基本原理是通过建立单极接地故障时电网的状态方程求解柔性直流电网中的短路电流。以张北可再生能源柔性直流电网试验示范工程为例,通过对比理论计算与系统仿真结果,证明了该方法的正确性与高效性。文中利用该方法分析了限流电抗器电感值等参数对短路电流的影响规律,为工程设计提供了一定参考。文章提出的计算方法可以广泛地适用于不同端数的基于模块化多电平换流器(modular multilevel converter,MMC)的柔性直流电网工程,为柔性直流电网工程的参数设计与直流断路器的选型提供支撑。

The magnitude of short-circuit current is very important for voltage source converter based high voltage direct current (VSC-HVDC) grid design and DC circuit breaker selection. This paper proposes a calculation method for line-toground short-circuit currents of bipolar DC grid that the neutral network consists of overhead lines. The principle of the method is to set up the state equations of the DC grid when the line-to-ground fault occurs,and to calculate the short-circuit currents by numerical calculation. Taking Zhangbei VSC-HVDC grid project as an example,this paper proves that the proposed method is accurate and efficient. In this paper,the influence of current-limiting reactor and other parameters on short-circuit current is analyzed by using the proposed method,which provides a reference for engineering design. The calculation method proposed in this paper can be widely used in different terminals of VSC-HVDC grid based on modular multilevel converter (MMC),which provides support for the parameters design of DC grid and the selection of DC circuit breakers.