Implementation of a urban distribution system digital twin in real-time

All countries must ensure sustainability and strengthen resilience while improving people’s health and welfare. For this reason, one of the needs remains for an accelerated path to meet global climate goals through the decarbonisation of our societies. Recently, the energy trends have confirmed the need to accelerate a reduction in CO2 emissions and Renewable Energy Sources (RES) are an enabling technology both to reach the goals and limit the rise in average global temperatures to 1.5 °C. As IRENA has estimated, RES, together with energy efficiency improving, could account for over 80% of the CO2 emission reductions needed. Despite this, RES-based solutions have not been explored to date with the rigor and urgency that is needed. However, the large penetration of RES involves some issues: for example, the presence of Distributed Energy Resources (DER) may include overvoltages in some nodes of the electrical grid that are impossible to control with traditional voltage control strategies that are centralised in HV/MV substations, like on-load tap changer, without negatively impacting the other feeders connected on the same busbar. Moreover, short-circuit currents could increase at the distribution system nodes with respect to the normal levels (without DER) due to the contribution of the Distribution Generation (DG) and, in worst case, they could exceed the short-circuit capability declared, affecting the protection device sizing inside the MV/LV substations. For these reasons, nowadays it is of utmost importance be able to predict the consequences that the penetration of RES would have in the electrical grid. To do that, digital twin is one of the most used methods. The purpose of this thesis is to implement a digital twin of a portion of the electrical grid of Turin for emulating the real behaviour of the network. A RTDS Simulator, made by RTDS Technologies Inc., was used for the implementation of the grid. It is a real-time simulator that runs electromagnetic transients and load flow analysis, especially for electrical power systems. The electrical grid analysed in this thesis is a model of a real urban distribution system of Turin. Specifically, Stura HV/MV substation in which there are three power transformers, one per each MV busbar, was simulated. However, only five MV feeders were implemented. For the LV level, two MV/LV substations were included. All the parameters relating to the structure of the system, the characteristics of the components and the loads connected are based on the data provided by the DSO that manages the electrical grid in the city of Turin. Regarding the protection system, the control logic of the relays associated to the various circuit breakers was implemented both by building block schemes made up of components from Controls library and using the setting provided by the Italian TSO and the above-mentioned DSO. The accuracy of the digital twin implemented was proved by simulating some fault conditions and by comparing the results with both fault theory and the ones obtained with OPARL-RT Simulator. With these tests, also the functionality of the protection system and its control logic, was verified. Starting from this model, other components, like photovoltaic systems or wind turbine generators, will be able to be added in order both to highlight potential failures in the network due to RES and to modify the protection system for considering the power generation at MV and LV level.