Optimal allocation of distributed reactive power resources under network constraints for system loss minimization

Reactive power control is an important control issue for distribution system operators due to increased penetration of distributed generation. The work presented in this paper utilizes the inherent reactive power capability of the doubly-fed induction generator (DFIG) based wind farms to optimize the system losses while considering the network constraints in the system. The IEEE-30 bus system was modified by installing DFIG based wind farms in the medium voltage (MV) region creating three wind clusters in the network. The steady-state analysis was conducted to illustrate the loss minimization capability of the DFIG based wind farms under different reactive power configurations. Reactive power participation for loss minimization was derived for each individual DFIG based wind farm to limit the control burden for the system operator and has shown the loss minimization performance for a range of wind farm control scenarios. The impact of dynamic line rating (DLR) was also investigated in the steady-state analysis and has shown that such capability can further enhance the loss reduction ability of the distributed VAr resources, in particular during high wind penetrations when transmission lines are heavily congested. The dynamic network analysis was carried out considering the Northern Ireland demand and wind power generation profiles with uniform and non-uniform wind conditions for three wind clusters defined in an IEEE-30 bus system. The dynamic network study has also shown that significant energy savings can be achieved by optimized reactive power dispatch of distributed VAr resources.