计及大规模电动汽车接入的配电网故障分析方法

Fault analysis method for an urban distribution network considering large-scale electric vehicle access

电动汽车保有量不断增加,故障发生时,V2G模式下电动汽车的放电电流会干扰配电网原有的故障电流,使配电网故障电流复杂多变且不易分析,传统的故障分析方法已难以适用。提出了一种计及大规模电动汽车接入的配电网故障分析方法。首先分析了电动汽车对配电网故障电流的影响程度。其次采用基于马尔科夫链的车辆转移矩阵对电动汽车出行行为进行模拟。然后结合电动汽车充放电规则,以电源出力的形式描述电动汽车的放电行为,建立了电动汽车放电等值电源模型。最后,以三相短路故障为例,基于有源配电网的故障分析方法对含大量电动汽车的配电网进行故障分析,得到了配电网各支路故障电流的时域变化特征。该分析方法建立的电动汽车放电等值电源模型能够体现电动汽车的放电特征,故障电流的分析结果能直观反映电动汽车放电行为对配电网各支路故障电流的影响程度和特征,可为含大量电动汽车的配电网保护整定方法提供理论依据。

The number of electric vehicles(EVs)is increasing.In the event of a fault,the discharge current of EVs in V2G mode will interfere with the original fault current of the distribution network(DN).This will make the fault current of the DN complex and difficult to analyze.Therefore,the traditional methods of fault analysis are hardly applicable.A fault analysis method of the DN considering the access of large-scale EVs is proposed.First,the influence of EVs on the fault current of the DN is analyzed.Secondly,the vehicle transfer matrix based on Markov chain is used to simulate travel behaviors of EVs.Then,combined with the charging-discharging rules of EVs,the discharge behavior of EVs is described in the form of power output,and the discharge equivalent power supply model of EVs is established.Finally,taking a three-phase short-circuit fault as an example,the fault analysis of a DN with a large number of EVs is carried out based on the fault analysis method of an active DN,and the time-domain variation characteristics of fault current of each branch of DN are obtained.The discharge equivalent power supply model of EVs can reflect their discharge characteristics.The analysis results of fault current can directly describe the influence degree and characteristics of EV discharge behavior on the fault current of each branch of a DN.They can also provide a theoretical basis for the protection setting method of a DN with a large number of EVs.