  In this paper, an open-source MATLAB toolbox is presented that is able to
generate synthetic, combined transmission and distribution network models.
These can be used to analyse the interactions between transmission and multiple
distribution systems, such as the provision of ancillary services by active
distribution grids, the co-optimization of planning and operation, the
development of emergency control and protection schemes spanning over different
voltage levels, the analysis of combined market aspects, etc. The generated
test-system models are highly customizable, providing the user with the
flexibility to easily choose the desired characteristics, such as the level of
renewable energy penetration, the size of the final system, etc.
