Integration of regulation in Multi-Terminal Direct Current grids design

Abstract: The supergrid denotes a transmission grid development option at European scalebased on large power corridors enabling to transport electricity from large productioncenters (such as large oshore wind farms) to large consumption centers.Technico-economic studies show that the development of supergrids could provideoverall benefits in terms of : economic welfare, security of supply and integrationof renewables at European scale. However, some regulatory issues, such asnon-harmonized financial regulatory models for grid investments and rules of coordinatedoperations among transmission system operators, are obstacles to realprojects implementation. In consequence it is of interest for the designer of gridtechnologies to integrate regulation early in the design process. The overall objectiveof the thesis it to propose a methodological approach enabling to integrateregulatory issues into design process. First, relevant regulatory issues are identifiedand classified. Second, a design method (method of technico-economic evaluationof grid technologies) which addresses selected regulatory issues is proposed. Last,the proposed design method is applied on a study case : the design of a power transmissioncorridor.First regulatory issue identified thanks to literature is that current planning methods(methods of assessment of expansion projects) do not measure properly theoverall benefits of supergrids. As a result, they do not make possible the harmonizationof financial regulatory models and eventually the actual development ofsupergrids. Second regulatory issue identified is the high uncertainty about futureoperating rules for two reasons : some current rules are not applicable to supegridsoperations and current security management methods are cost-inecient ina context with several transmission system operators. A general alternative designmethod consistent with future standard planning methods is chosen to address firstregulatory issue. That method is a risk-based cost minimization problem where anoptimal trade-o between technical costs and reliability costs is pursued by simulationof the power system. It relies on a probabilistic description of operatingconditions. The recommendation formulated regarding the second regulatory issueis that the application of the general design method to particular cases requires acase-per-case assessment of operating rules uncertainty. The case study illustratesvthe application of the proposed design method. First, relevant operating mechanismsare identified (system reduction). Then, system cost functions are expressedbased on the reduced power system representation. Additionally, simulation modelsare developed, implemented (on Python) and used to compare several power transmissioncorridor architectures.In conclusion, a risk-based method consistent with standard planning methodscurrent development seems the most appropriate design method to be used and uncertaintyabout future operating rules should be taken into account while applyingthe general design method. The reports shows that such a risk-based method enablesto discriminate between technologies. As a result, it seems a suitable decisiontool for the supergrid designer.