Optimal voltage controls of distribution systems with OLTC and shunt capacitors by modified particle swarm optimization: A case study

Abstract

This paper presents a new framework to determine the optimal voltage control of distribution systems based on modified particle swarm optimization. The problem is to determine the set-points of the existing regulation devices such as on-load tap changers, shunt capacitors, etc. which minimizes the multi-objective function including power losses, voltage deviations, switching operations while subject to the constraint of allowable voltage levels, switching stresses, line capacity, etc. The problem is formulated and solved by modified particle swarm optimization methods with the trial, test and analysis techniques due to its large-scale and high nonlinearity property. In each iteration, a Newton-Raphson-based simulation is run to evaluate the performance of the regulation devices and the distribution system as well. The convergence is guaranteed by defining neighborhood boundaries for each trial. The proposed method is applied in a practical case study of 15-MVA, 22-kV, 48-bus distribution systems in Vietnam. The result of simulations shows that the voltage profile can be improved significantly with no bus voltage out of the boundaries while the voltage deviations is reduced as much as 56.5% compared to the conventional nominal setting. In the case study, the power loss is not improved much (1.21%).