Voltage and power control for minimising converter and distribution losses in autonomous microgrids

Voltage source converters (VSCs) are widely used in microgrids to interface the renewable resources with the electrical network. In autonomous microgrids with the dc distribution network, the optimal dc voltage reference for the one VSC that operates in the voltage regulator mode and the optimal reference power settings of the remaining VSCs working in the power dispatcher mode have to be pre-determined. Emulating the utility grid, these settings and control modes are commonly selected such that the dc voltage is maintained within desired margins, typically ±10% around the rated value. In this study, the objective function is minimisation of the converter and distribution line losses. All the operational modes and limits of VSCs have been taken into account. Genetic algorithm has been utilised in solving the optimisation problem. Owing to limited available power from renewables, reducing the converter and distribution system losses will enhance the survivability of the microgrid and ease the cooling requirements, resulting in a more compact system. A model of a 20-bus microgrid with the dc distribution network is employed to verify the effectiveness of the presented optimisation algorithm.