Linearized Optimization for Reactive Power Dispatch at Transmission Grid Level considering Discrete Transformer Tap-Settings

Research indicates that an efficient operation of power systems, requires the use of optimization techniques for minimizing objectives such as grid losses, dispatch costs, reducing potential technical constraint violations etc. These are referred to as optimal power flow (OPF) techniques. Over the years different optimization techniques have been developed based on analytical methods, heuristics and stochastic based approaches. Analytical methods include for example linear and quadratic optimization approaches. Metaheuristic methods like Particle Swarm optimization (PSO) and Genetic Algorithms (GA) have also been developed and researched upon. In this paper, a successive mixed integer linear optimization programming (sMILP) based method in the context of optimal reactive power flow (ORPF) is developed considering continuous reactive power flexibilities and discrete transformer tap-sets. The novel formulation of the transformer tap sensitivities indicate its efficiency of using discrete tap-settings and ease of implementation in the context of Linear Programming. This method is further compared to an already established PSO-based method subject to similar initial grid conditions and three different voltage constraint violation case studies. Results indicate the reliability and efficiency of the method.