Abstract
The purpose of this project memo is to give some answers to the question: “How to model – for long-term transmission grid planning purposes – the operation of a future power system with AC grids coupled with DC grids?”. It is a deliverable of the DeCOOP KSP project (“Development of coupled offshore and onshore power grids”), whose objective is to establish the knowledge basis and methodologies necessary for developing a socio-economically profitable and robust coupled offshore and onshore grid. This includes modelling a future power system with significant presence of both DC and AC grids, in a way that is simple and computationally efficient enough to be possible to use as part of studies spanning analysis horizons of several decades. The memo starts by giving an overview of power flow models, including optimal power flow models (OPF) and security-constrained optimal power flow models (SCOPF), that are currently used for modelling AC grids as in the current onshore power system. It then surveys the state of the art for power flow models extended for modelling hybrid AC and DC grids. Recommendations are given for how further work in KSP DeCOOP could build upon existing tools and code bases. As the first steps, an existing SCOPF research code will be extended to be able to model coupled AC and DC grids and to account for power losses.