In order to study the impact of inter-connection of distributed generators (DGs) on steady state voltage stability of distribution network

the voltage stability index (VSI) capable of reflecting the degree of voltage stability of all load buses in distribution network is derived. A new load increase strategy for distribution network is proposed to quantitatively analyze the voltage stability of the weakest bus and the whole system. Causes of distribution network voltage collapse are discussed using PV curves

and the effects on steady state voltage stability in centralized and distributed inter-connection mode are compared when DG output varies dramatically. Furthermore

a voltage stability analysis method based on the calculation of VSI value of all buses is proposed to rapidly rank the voltage stability margin of load buses as well as accurately locate the weakest bus. Simulation results prove that rational location of DG inter-connection is expected to improve voltage stability of the entire network. This work is supported by Post-doctoral Science Foundation of China (No. 2014M552080) and State Grid Corporation of China (No. 5211011400BT).