多端混合UHVDC单极接地故障的半解析仿真法

Semi-analytical simulation of a multiterminal hybrid UHVDC single-pole grounding fault

针对现有特高压直流工程直流故障仿真模型未考虑控制系统以及其纯数值仿真速度慢的问题,提出了一种多端混合特高压直流工程的半解析仿真法。首先,在直流单极接地故障下,建立了考虑控制器动态的常规和柔性直流换流站实用模型。然后,进一步建立了典型三端混合特高压直流输电工程的直流单极接地故障仿真模型,并使用多阶段半解析法求解。多阶段半解析法的核心思想是将仿真时段均分成多个子区间,并在每个子区间上求近似解析解。该方法融合了解析方法和数值方法的优势,并有利于开展并行计算。最后,将所得结果与PSCAD/EMTDC、欧拉法和4阶龙格库塔法等常用数值解法进行比较。结果表明,所提方法能得到与PSCAD/EMTDC高度吻合的仿真波形,且速度远快于常用数值解法。

There is a lack of a controller in existing DC fault simulation models of ultra-high voltage direct current(UHVDC)projects.Also their pure numeric simulation is slow.Thus a semi-analytical simulation method is proposed for a multiterminal hybrid UHVDC.First,practical models of both conventional DC and flexible DC converter are established considering controller dynamics.Secondly,a DC single-pole grounding fault simulation model for a typical three-terminal hybrid UHVDC is built and then analyzed using a multistage semi-analytical method(MSAM).In the MSAM,the simulation period is evenly divided into several small intervals,and an approximate analytical solution is obtained for each interval.The advantages of analytical methodology and a numerical algorithm are united in MSAM,where parallel computing is also easy to implement.Lastly,the simulation results of the MSAM are compared with those of PSCAD/EMTDC and common numerical methods(Euler method and 4th order Runge-Kutta method).The simulation waveforms of the MSAM match with PSCAD/EMTDC very well with a significantly higher simulation speed than the common numerical methods.