The rapid growth in electric vehicle (EV) adoption, particularly in densely populated urban areas, together with the global aim of reducing greenhouse gas emissions, is placing increasing stress on existing power distribution infrastructure. Bipolar DC microgrids present a robust and flexible solution for integrating daily DC loads such as lighting networks and EV chargers, offering higher efficiency due to fewer power conversion stages compared to the AC grid system. This project focuses on developing a cost-effective, reliable and easily deployable EV charger that enables seamless integration of DC microgrids into today’s AC-based urban systems, leveraging the existing Dutch public lighting network. By utilising the already-installed AC grid combi cables with 6mm2 auxiliary copper conductors, the proposed converter operating at ±350V (700V bipolar DC) and 15A with rated power of 11 kW can deliver power directly to dual street-side parking spots while preserving sufficient current capacity for lighting loads. The goal is to enable practical low-power charging in locations where vehicles remain parked for extended periods, such as overnight or during working hours. High reliability and minimal maintenance needed are key requirements to support the large-scale deployment of DC-based EV charging in urban environments.
A comprehensive review and comparison of wide-bandgap semiconductor technologies and isolated DC-DC converter topologies for dual-output, bidirectional operation led to the selection of a SiC-based Triple Active Bridge (TAB) as the most balanced solution in terms of performance, reliability, complexity and cost. The TAB converter is an evolution of the conventional Dual Active Bridge (DAB) topology, enabling direct power transfer between three ports. The inclusion of a third port, however, increases the complexity of power flow management as a single core transformer allocates the three windings. A detailed theoretical analysis, supported by open-loop simulations, guided the parameter design of the converter to ensure zero-voltage switching (ZVS) across all charging scenarios. The full mathematical expressions of the transformer’s AC currents, obtained through Fourier series decomposition of the full-bridge voltages, allowed comparing different current measurement approaches for closed-loop DC current control. Implementing the control strategies under real operating conditions required investigating scenarios such as the sudden disconnection of one EV and single-vehicle charging. These cases deviate from the typical three-port operation and are critical to analyze in order to ensure safe and efficient performance. Building on these results, a passively cooled hardware prototype was developed, integrating the power semiconductors, high-frequency transformer, filters, protections, and thermal management. Experimental validation confirmed the converter’s functionality, demonstrating a complete workflow from concept to prototype for an EV charger designed to be integrated in the emerging DC microgrid infrastructure.