Practical Demonstration and Novel Optimization Control for a Smart Soft Open Point to Maximize the Synergy Between the DC Metro Line and the LV Distribution Grid

The steady increment in electrical loads often requires expensive and disruptive upgrading of the electrical power supply infrastructure. This can be avoided by synergizing the dc railway networks with local ac grids using soft-open points to transfer the available regenerative braking energy of the trains to the nearby local grid. Besides, a battery energy storage system is integrated into the soft-open point to match the braking events with the grid load power, so that the new developed system effectively decouples both the rail and grid networks. This article presents a practical study for such novel rail + grid energy management strategy. A 100-kW smart soft open point is designed and implemented in this research to experimentally evaluate the new strategy in a laboratory environment using real rail data. Afterward, the developed 100-kW prototype is accordingly validated in the real environment at Metro Madrid, Spain. Last, a multiobjective optimization framework is designed for the developed management system to maximize the synergy between both networks. The multiobjective framework aims to minimize the power losses in both networks, maximizing the profit of selling the harvested rail power to the grid and finally maximize the penetration level of the available renewables power in the grid.