Based on a newly developed simulation platform, this paper proposes a fully distributed phase-independent voltage regulation strategy. The strategy offers both real and reactive power support options from distributed energy resources (DERs) and accommodates the impact of different R/X of the lines and different topologies of a distribution network. A linear sensitivity analysis is first carried out to explain the essential impact mechanism of R/X on the voltage sensitivity. Then a perturbation approach, as the substitute of conventional Jacobian analysis, is employed for an accurate voltage sensitivity analysis on a three-phase unbalanced nonlinear distribution network model. The impact of R/X on the voltage sensitivity is quantified, which can then be used to indicate which type of power and critical bus can provide the most effective voltage support under the specific R/X in the planning stage of the regulation strategy. It also provides a guidance for DERs droop constant tuning during the operational stage to ensure the effectiveness of the proposed strategy. The voltage regulation includes two stages: the first is consensus stage based on the consensus algorithm to achieve an average voltage deviation without the need of central controllers; the second is droop control stage to proportionally allocate the available P/Q of DERs. The modified IEEE-13 bus distribution network with different R/X and topologies is used for the case study. Results verify that the proposed regulation strategy can effectively deal with the unbalanced voltage problems in the network.