城市配网改造下中压直流配电网的供电能力分析

Research on the Power Supply Capacity of Medium Voltage DC Distribution Network in Urban Distribution Network Transformation

我国的城市配电网正面临供电能力不足的压力,中压直流配电方式的出现为城市配电网的改造提供了一个新的思路和方法。基于可靠性和适应性的要求,本文选择双极三线制作为直流配电网的接线方式。首先考虑交直流线路的过电压水平,确定了交直流配电网额定电压的关系。在此基础上,从电压损耗、功率损耗以及供电容量3个方面,对中压交、直流配电网的供电能力进行了理论推导,建立了交、直流配电网供电能力的通用模型。并以常用的中压电缆YJV-300为例,分析发现中压直流配电网的供电能力显著优于中压交流配电网。特别的,本文研究了直流配电网线路发生单极故障时的供电能力,发现其供电能力相对于交流配电网而言也具有一定的优势。

Chinas urban distribution network is facing the pressure of insufficient power supply capacity.The emergence of medium voltage DC（MVDC）distribution mode provides a new idea and method for urban distribution network transformation.Considering the reliability and adaptability,bipolar three-wire connection mode is selected as the connection mode of MVDC distribution network.Firstly,the rated voltage relationship between AC and DC distribution network is determined by considering the over-voltage level of the AC and DC lines.Then,the power supply capacity of MVDC and MVAC distribution networks is deduced from three aspects of voltage loss,power loss and power supply capacity,and the universal model of power supply capacity for AC and DC distribution network is built.Finally,by taking commonly used medium voltage cable YJV-300 as example,analysis shows that the power supply capacity of MVDC distribution network is significantly superior to that of MVAC distribution network.In particular,the power supply capacity of the DC distribution network is studied when monopole grounding fault occurs,and it is found that the DC power distribution network also has a certain advantage on power supply capacity by comparing to AC distribution network.