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The paper aims at describing a model-based approach to design automation logics for fault location and supply restoration in medium voltage distribution networks. The application of automation functions along medium voltage feeders and, in particular, the installation of protection devices in secondary substations mandates the design and the implementation of complex logics to coordinate the operations of this hardware in case of fault occurrences. This synchronization is realized with the exchange of IEC 61850 GOOSE messages, but the correct usage of this information must be implemented in each protection device through dedicated logics, which are not in the common out-of-the-box system configurations. To support the introduction and the design of these logics, an automata-based approach has been proposed and successfully demonstrated in a real environment in the European research project IDE4L. This formal methodology has been introduced to simplify the design phase and to standardize the logics implemented in the protection prototypes realized in the project. The same models have also been used in the implementation phase with a semi-automatic code generation procedure, considering as a target system the software programmable logic controllers (soft-PLCs), available on the protection devices. Based on the test results and the short time to set up the test bench, this approach proved to be a reliable and effective way to implement complex medium voltage (MV) automation logics such those needed in modern smart grids.

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The high-penetration of Distributed Energy Resources (DER) in low voltage distribution grids, mainly photovoltaics (PV), might lead to overvoltage in the point of common coupling, thus, limiting the entrance of renewable sources to fulfill the requirements from the network operator. Volt-var is a common control function for DER power converters that is used to enhance the stability and reliability of the voltage in the distribution system. In this study, a centralized algorithm provides local volt-var control parameters to each PV inverter, which are based on the electrical grid characteristics. Because accurate information of grid characteristics is typically not available, the parametrization of the electrical grid is done using a local power meter data and a voltage sensitivity matrix. The algorithm has different optimization modes that take into account the minimization of voltage deviation and line current. To validate the effectiveness of the algorithm and its deployment in a real infrastructure, the solution has been tested in an experimental setup with PV emulators under laboratory conditions. The volt-var control algorithm successfully adapted its parameters based on grid topology and PV inverter characteristics, achieving a voltage reduction of up to 25% of the allowed voltage deviation.