Improved normalised normal constraint method to solve multi-objective optimal power flow problem

This study proposes an improved normalised normal constraint (NNC) method for solving optimal power flow (OPF), which is formulated as a multi-objective problem. While NNC is an efficient solution method to solve multi-objective problems, it may not cover the entire Pareto frontier in the objective space when three or more objectives are present in the problem, i.e. when the Pareto frontier becomes a hyper-surface. This research work aims to solve this limitation of NNC and propose a more effective solution method, named improved NNC (INNC), for multi-objective optimisation problems with three or more objective functions. The proposed INNC is applied for solving multi-objective OPF problem with three objectives of generation cost, transmission loss and voltage regulation. The effectiveness of the proposed INNC method for solving the multi-objective OPF problem is extensively illustrated on the IEEE 30-bus and IEEE 118-bus test systems in comparison with several recently published multi-objective solution approaches.