Research On New Topologies Of Hybrid AC/DC Microgrid And Their Reliability

Microgrid is an autonomous system,which can achieve flexible switching between islanding and grid-connected operation.It helps improve the reliability of load and improve the utilization efficiency of distributed power,and is an important part of smart grid in the future.According to the type of topological,microgrid can be divided into AC microgrid,DC microgrid and hybrid AC/DC microgrid.The hybrid AC/DC microgrid integrates the advantages of the AC microgrid and the DC microgrid.It not only provides a small retrofit to the existing power grid,but also greatly reduces the commutation equipment required for the DC distributed power and load access to the power grid.It is one of the developing directions of future smart grid.This paper introduces the topology types of the existing hybrid AC/DC microgrid and analyzes the characteristics and applying scope of the existing topology.Referring to the topology of the existing microgrid and considering the composition and operation mode of the hybrid AC/DC microgrid,three new topologies of hybrid AC/DC microgrid are proposed.The flexibility and reliability of the new topologies and the existing topology are compared to point out the applicable situations of the new topologies.Taking a university in Beijing as an example,a suitable hybrid AC/DC microgrid topology is selected for it.Based on the reliability analysis method of distribution network and considering the influence of distributed power and load island operation,a reliability analysis method suitable for microgrid is obtained.The influence of distributed power and key components on the reliability of hybrid microgrid is analyzed by using that method.The reliability of the existing topology and the new topology proposed in this paper are compared and analyzed.By comparing the different requirements of the reliability assessment of the hybrid microgrid connected to the grid and the island operation,some indexes to describe the reliability of mixed microgrid in isolated island operation are put forward accordingly.The reliability of the isolated island operation is analyzed by the index presented in this paper.