For revealing the influence of input power on systems voltage stability and system loss of wind power and the role of reactive power compensation and also for such drawback as qualitative analysis in the past study and influence of unit injection on wind power system

in this paper several indexes for characterizing influence of active injection of wind power on voltage stability and system loss are introduced: Active power loss ηP

specific reactive power loss ηQand specific voltage offsetΔV/P. It is shown by the study that reactive power compensation can expand injection power limit of wind power

but

due to increase of reactive power loss of low voltage circuit of wind power with the increase of active power

is far from making up the negative effect because of continuous increase of the injection active power;At the same injection power of wind power

the reactive compensation can reduce effectively system loss and improve voltage stability and the effectiveness of the index proposed in this paper is illustrated through calculation analysis.