A MINLP technique for optimal placement of multiple DG units in distribution systems

Loss reduction is one of the prime objectives for planning of distributed generation (DG). To improve performance of distribution systems, optimal placement of distributed generator is critically important, as DG benefits are site and size specific. Optimal placement of multiple DG units is non-convex and non-linear optimization problem. The methodology proposed in this paper solves Mixed Integer Non-Linear Programming (MINLP) formulation for loss minimization. The proposed methodology simplifies the problem by dividing it in two phases, namely Siting Planning Model (SPM) and Capacity Planning Model (CPM) thereby reducing the search space and computational time. The SPM model selects the candidate buses based on Combined Loss Sensitivity (CLS). In CPM, optimal locations and sizes are obtained by integrating Sequential Quadratic Programming (SQP) and Branch and Bound (BAB) algorithm for MINLP problem. The performance of the proposed method is tested on IEEE 33-bus and IEEE 69-bus distribution system for placement of single and multiple DG units capable of delivering either real or both real and reactive power. The obtained results are then compared with three basic classes of optimization methods, viz., Exhaustive Load Flow (ELF), Improved Analytical (IA) and Particle Swarm Optimization (PSO). The key advantage of the proposed method is that it simultaneously considers placement of multiple DG units giving better optimal solution in reasonably less computational time.