基于有效值的台区电流不平衡度计算方法研究*

为解决在相位信息缺失条件下三相电流不平衡度准确计算的难题,提出了一种基于基波电流有效值的低压台区电流不平衡度计算方法。文章分析了基于对称分量法的电流不平衡度计算方法,以及在相位信息缺失条件下,4种常用三相电流不平衡度工程计算方法的差异性;基于对称分量法分解规律,将三相不平衡电流相量分解为两组相位对称的电流相量。在相位对称条件下,推出基于基波电流有效值的电流不平衡度计算式,确定不同工况下两组电流不平衡度的主从关系;结合低压台区负荷电流的不平衡特性,分析了计算方法在低压台区三相电流不平衡度计算中的适用性及差异性,并对低压台区运行数据进行实测验证。与4种常用工程计算方法相比,所提方法与对称分量法计算结果更加接近,且基本一致。

Study on calculation method of unbalance factor based on RMS of fundamental current

In order to solve the problem that it is difficulty to accurate calculate the three-phase current unbalance factor when missing the phase information, a method based on the effective value of fundamental current was proposed. Firstly, this paper analyzes the calculation method of three-phase current unbalance factor based on symmetrical component method, and the difference of four commonly used engineering calculation methods of three-phase current unbalance factor when missing the phase information; Secondly, based on the decomposition law of symmetrical component method, the three-phase unbalanced current was decomposed into two groups of current phasors which is phase symmetrical, the calculation formula of current unbalance factor based on the effective value of fundamental current is derived when the phase symmetry, then determine the master-slave relationship between two groups of current unbalance factor under different working conditions; Finally, the applicability and difference of the calculation method in the calculation of three-phase current unbalance factor are analyzed based on the unbalanced characteristics of load current in the low-voltage district, and the operation data in the low-voltage district are measured and verified, Compared with the four commonly used engineering calculation methods, the calculation results of the method and the symmetrical component method are more close and basically consistent.