电网三相不平衡的度量与治理综述

Review of the measurement and control of three-phase unbalance

近年来,电网中的各类电能质量问题愈加受到重视,对于三相不平衡问题,国內外学者做了大量研究工作,需要系统地分析和整理。三相不平衡由电网中的负序和零序分量引起,国际电工委员会(IEC)提出以负序和正序分量之比值来度量不平衡。由于序分量获取困难,工程中常以量测电压、电流有效值来度量三相不平衡,这类方法形式不统一,且与序分量度量形式不对应,统一的不平衡度量方法亟待构建。三相不平衡主要通过电容型补偿、电力电子变流器型补偿和换相补偿治理。电容型补偿可以实现连续调节但是无法降低线损;换相只能离散投切,无法连续调节。未来应当结合换相与附加补偿手段来治理三相不平衡,获得更好的补偿效果。

The negative sequence and the zero sequence component cause three-phase unbalance.IEC proposes to measure the imbalance with the ratio between negative sequence and positive sequence component,ignoring the xero sequence component.Because of the difficulty in obtaining the sequence component,the RMS value of the measured voltage and current is often measured in the project.In contrast,such metrics exist in many forms and do not correspond to the order component metrics.It is urgent to construct a unified unbalance measurement method to considering the zero sequence and the non-correspondence between the quantity measurement and the sequence component.Three-phase unbalance control mainly relies on capacitive compensation,power electronic converter type compensation and commutation.Among them,capacitive compensation can achieve continuous adjustment but can not reduce line loss.Commutation can only be discretely switched and cannot be continuously adjusted.In the future,these two methods should be combined to manage the three-phase unbalance,in order to optimize the compensation effect.