Design of a Reduced Scale Prototype for a SiC-based HVDC Hybrid Circuit Breaker for the New Italian HVDC Network

The recently developed High Voltage Direct Current circuit breakers (HVDC-CBs) prototypes could represent a breakthrough in terms of flexibility for the future HVDC grids. Several design are currently being investigated by different manufacturers (mainly in EU, China, Japan), each with its own potential advantages and disadvantages. HVDC-CBs models for electromagnetic transient studies have been also developed, to evaluate both the CB performances and its impact on dc grids, most significantly, the switching overvoltages. Terna S.p.A, as part of the 'Hypergrid' project, started the development of a small scale HVDC-CB mock-up, aiming at a better understanding of the transient behaviour, protection strategies and switching overvoltages of the future meshed dc grids. The mock-up will include a silicon carbide (SiC) MOSFET as the main CB switch; this seems a promising solutions for future HVDC-CBs, due to the superior performances of SiC components in terms of blocking voltages capability and maximum operating temperature. The paper deals with the design of the HVDC-CB mock-up and the attendant electromagnetic transient simulations, with a specific focus on the expected overvoltages and polarity reversal upon circuit breaker opening.