Power electronic technology is used to achieve AC/DC conversion in the flexible grid

it can realize long distance power transmission and make use of power efficiently. In the DC micro-grid

there is no enough reactive power to support the voltage maintains a normal level

thus the voltage decreases in large amplitude

which would not meet the power quality demand

it’s easily to cut supply line by the third line of the grid that caused by low level of voltage

meanwhile

it leads to safety and stability problem in the local grid. In this paper

flexible grid is analyzed to build the calculation model

using this model to analyze the low voltage character

Reactive power compensation which is used in the end of lines and the DC power point

with such method

the low voltage can be satisfied the demand of power quality.