Optimal allocation and sizing of DG units considering voltage stability, losses and load variations

• DG allocation with a new index for voltage stability and power losses.
• A long-term scheduling for optimal allocation and sizing of DG unit.
• A general equation of generation for different loading condition.
• DG allocation problem is solved using ICA and verified by CSA.
• The DNOs generation scheduling has been facilitated over the planning horizon.

This paper proposes a new index to determine the optimal size and location of DG units, in order to minimize active power losses and enhance voltage stability margin considering load variations. A modified form of Imperialistic Competitive Algorithm (ICA) method is used to solve the optimization problem. To provide a comprehensive perspective for network scheduling, the load variations are considered. The load linear changes are from 50% to 150% of the base load (in 1% steps). At each step, the optimal size and location of the DG unit are determined and then, general expressions for DG sizes as a function of load level are concluded through curve fitting technique. These general expressions can be used as a suitable tool for network planning.The proposed method is applied to 34-bus and 69-bus test systems and the results are compared with the results obtained from cuckoo search algorithm in order to validate the proposed methodology.