In addition to increasing penetration of distributed generation (DG)

the distribution system power flow may be significantly impacted by direction and magnitude. This paper proposes a method for optimal placement of wind DG considering the unbalanced operation of distribution systems. The objective function includes static voltage stability index

three-phase unbalance index

system reliability index

and DG investment cost. The untransposed distribution lines and unbalanced load are modelled

and corresponding static voltage stability index and system reliability considering DG penetrations are derived. The expected and stochastic daily distributed generation and demand profiles in four seasons are calculated to improve the accuracy. To solve this multi-objective optimization model

a fuzzy membership function is used to integrate the four individual objectives

and a sensitivity-based method is proposed to solve the model efficiently. Case study on IEEE 13-bus distribution 3-phase networks and 123-node test feeder successfully verifies the performance of the proposed approach.