To address issues of three-phase unbalance, increased voltage deviations, and higher network losses caused by single-phase integration of distributed photovoltaic (DPV) systems, an optimal operation method for three-phase unbalanced distribution networks considering DPV reactive power-voltage droop control is proposed. First, based on voltage deadbands and saturation intervals, the reactive power-voltage droop control characteristics of DPV inverters are characterized, and a multi-timescale optimization framework is established. Then, conventional voltage regulation devices are coordinated at the long timescale to determine the adjustable reactive power capacity boundary of DPV, while the droop control parameters of DPV inverters are optimized at the short timescale. Finally, semidefinite relaxation and second-order cone relaxation are employed to transform the nonconvex nonlinear model into a mixed-integer second-order cone programming model, and minute-level operational validation is conducted to verify the control performance. Case studies demonstrate that the proposed method achieves coordinated multi-timescale optimization, reduces three-phase unbalance and network losses, and mitigates voltage deviations.