In this work a new UPFC based dual PI controller is presented, whose gains are tuned by Improved GWO technique. The controller is used to damp low frequency oscillation in the power system. The disturbance considered is step rise in input mechanical power to generator. The ITAE criterion is selected for optimization problem. Standard popular techniques PSO & DE are also employed to tune dual PI controller parameters. In dual PI controller, simultaneously two actions of UPFC are performed, which are modulation index of series (mB) and phase angle of shunt (ôe) converter to damp power system oscillations. From system response and eigen values, it is observed that dual PI controller shows better result than conventional PI controller. Also IGWO technique provides much better result as compared to PSO & DE technique to design dual controller.