主电路参数对MMC-HVDC电网直流短路故障电流综合影响分析

Analysis of Comprehensive Influence of Main Circuit Parameters on DC Short Circuit Fault Current of MMC-HVDC Grid

针对模块化多电平变换器的高压直流(MMC-HVDC)电网的结构复杂多样,难以构建直流短路故障电流的精确解析分析模型的问题,提出一种基于中心复合实验设计的分析方法用于定量分析和评价主电路参数对直流短路故障电流的综合影响。该方法通过中心复合实验设计,以尽可能少的直流短路电磁暂态仿真实验数据获得故障后6 ms内直流短路故障电流的多因子回归方程,从而对多因子的综合影响进行定量分析和评价。以四端直流电网为例,设计了分析直流电感、桥臂电感和中性线电感以及接地电阻4个主电路参数对直流短路故障电流影响的多因子仿真实验,利用统计学方法分析和评价了各因子对直流短路故障电流峰值的主要影响和交互作用的影响。分析结果表明:4类主电路参数中,直流电感对故障后6 ms内故障电流峰值的影响程度最强,中性线电感对故障后6 ms内桥臂故障电流峰值的影响程度最强,主电路参数间的交互作用可忽略不计。该分析结果为直流电网短路故障情况下故障电流抑制研究和多元件参数综合优化提供理论依据。

Due to the complexity of the modular multilevel converter based high voltage direct current(MMC-HVDC)grids,it is difficult to build an accurate analytical model for analysis of direct fault currents.In this paper,an analytical method based on central composite design(CCD)is proposed to quantitatively analyze and evaluate the comprehensive influence of main circuit parameters on DC short-circuit fault current(DSCFC).By the proposed method,the multi-factor regression equation is obtained with as few simulations experimental data as possible to realize quantitative analysis and evaluation of the comprehensive influence of multifactors on DSCFC.Taking the four-terminal DC grid as an example,multi-factor simulation experiments are designed to analyze the influence of the four main circuit parameters including DC inductance,bridge arm inductance,neutral line inductance,and ground resistance on DSCFC.The statistical method is used to analyze and evaluate the main effects and interaction effects of each factor on the peak value of the DSCFC.The analysis results show that among the four main circuit parameters,the DC inductance has the strongest influence on the peak value of fault current within 6 ms after the faults,the neutral inductance has the strongest influence on the peak value of bridge arm fault current within 6 ms after faults,and the interactions between main circuit parameters are weak and can be ignored.The analysis results can provide a theoretical basis for the research of fault current suppression and the comprehensive optimization of multi-component parameters in the case of short-circuit fault in DC grid.