A multi-objective planning approach for optimal DG allocation for droop based microgrids

This paper proposes a multi-objective planning approach to determine the optimal DG locations for droop-based microgrids. A secondary control operating region is mathematically formulated and incorporated in the multi-objective optimization problem to constrain the optimal droop characteristic within the acceptable frequency and voltage thresholds. The proposed planning problem is formulated as a Mixed Integer Non-Linear Programming (MINLP) problem and is tested on a modified version of the IEEE 38 bus system operated as an islanded microgrid. The proposed approach is applied to the three most common microgrid control strategies: P-f/Q-V droop, the P-V/Q-f droop and master/slave. The proposed formulation is compared to existing planning algorithms for droop-based microgrids. The results show that including the secondary control region in the optimization problem achieves lower voltage deviations and no frequency deviations at all demand levels. The optimal DG allocation solution may vary from the cases where the droop gains or references are fixed.