直流配电网电能质量指标定义及关联性分析

Definition and Correlation Analysis of Power Quality Index of DC Distribution Network

直流配电网以供电能力强、可控性好、高效可靠和适应可再生能源接入等优势,已成为未来配电系统的发展方向。直流电能质量是规划、设计、运行和控制的核心问题之一,而源荷波动性、扰动多样性和功率变换设备敏感性使其呈现新的特点。该文首先分析交直流电能质量的差异,对比交流电能质量体系,依据国内外相关文献及标准,对直流谐波、电压波动与闪变、电压暂降、电压不平衡、电压偏差等进行定义,从而构建直流电能质量指标体系。由于直流电压的零频特性及直流配电网特殊结构,不同的直流电能质量现象之间存在明显的关联性,该文对谐波与波动、偏差与稳态不平衡、暂降与暂态不平衡间的关联性进行分析,指出其在直流电能质量评估、指标限值制定等方面的重要作用。选取直流配电网典型案例,分析不同工况下各个电能质量现象的产生机理,依据指标定义推导指标与相关参数的定量关系,通过Matlab/Simulink搭建模型,对产生机理及指标关联性进行验证。

With the advantages of controllability, efficiency and flexible access to renewable energy, DC distribution network has become the development direction of distribution network at home and abroad. DC power quality is the core issue of its planning design and operation control, but the source and load fluctuations, diversity of disturbances and the sensitivity of power conversion equipment make it present new features. This article first analyzed the differences between AC and DC power quality, compares the AC power quality system, and defines the DC harmonics, voltage fluctuations and flicker, voltage sags, voltage unbalances, voltage deviations, etc. Due to the DC voltage characteristics and the special structure of the DC distribution network, there are obvious correlations between different DC power quality phenomena. This article analyzed the correlation between harmonics and fluctuations, deviations and stable unbalances, sags and transient imbalances. Finally, a typical case of DC distribution network was selected to analyze the mechanism of each power quality phenomenon under different operating conditions. Based on the quantitative relationship between the index definition and the relevant parameters, a model was built by Matlab/Simulink to verify the generation mechanism and the correlation of the indexs.