Flexible General Branch Model Unified Power Flow Algorithm for Future Flexible AC/DC Networks

Abstract

This paper presents a new Flexible General Branch Model (FGBM) for the power flow solution of hybrid AC/DC grids. The model is an improvement of MATPOWER's original branch model, by incorporating extra degrees of freedom in form of additional state variables to model both conventional AC branches as well as different types of AC/DC interface devices such as Voltage Source Converters (VSC). A detailed description of the proposed flexible model is shown. Furthermore, the model is used in a new unified power flow algorithm based on the Newton Raphson method. This algorithm is also an extension of the already powerful one employed in MATPOWER. Due to the nature of the developed model, there is no need of identifying or differentiate between AC, DC or even VSC nodes. As a result, all power flow calculations are obtained with the traditional NR method. Power and Voltage Control variables are created for all the modelled elements that requires them. Necessary modifications to the original MATPOWER's power flow algorithm to include them are developed and described. Finally, detailed simulations validate the algorithm and model's accuracy.