交直流配电网可靠性对比

Reliability Comparison of AC and DC Distribution Network

为探索高可靠性配电网的发展方向,首次就中压柔性直流配电网的可靠性进行深入研究。建立了换流站、直流变压器和直流断路器的可靠性模型,考虑直流负荷、备用电源和分布式电源的影响,对最小割集法进行改进使其同时适用于交、直流配电网的可靠性评估。以"手拉手"环状网络为例,对比了现有技术条件下交、直流配电网的可靠性。研究表明,现阶段直流配电网的可靠性低于交流配电网;随着直流负荷比例的增大,直流配电网可靠性将得到提高,但效果有限;直流断路器和直流变压器的高故障率才是制约现阶段直流配电网可靠性提高的关键因素。随着电力电子元件的发展,直流配电网的可靠性将逐步接近甚至超越交流配电网。

To explore the development direction of high reliable distribution network in future, it was the first time to research the reliability of medium-voltage flexible DC distribution network in depth. The reliability models of VSC converter station, DC/DC transformer and DC circuit breaker were established; considering the impacts of the DC load, the reserve power supply and distributed generation, the minimum-cut set method was improved to make it suitable for the reliability assessment of both AC and DC distribution networks. Taking loop distribution network for example, the reliability of AC distribution network and that of DC distribution network under existing technical conditions were compared. Comparison results show that at the present stage the reliability of DC distribution network is lower than that of AC distribution network; with the increase of the proportion of DC load the reliability of DC distribution network will be improved, however the effectiveness will he limited; the high failure rate of DC circuit breaker and DC/DC transformer is the very factor that restricts the reliability improvement of DC distribution network at the present stage. With the progress of power electronic elements, the reliability of DC distribution network would be close to that of AC distribution network gradually and even higher than that of AC distribution network.