A Generalized Procedure to Develop DC Switchyard for MTDC Grids

With the advent of Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) technology, Multi-Terminal DC (MTDC) grids are gaining popularity and becoming reality. Half-bridge based Modular Multilevel Converter (H-MMC) along with Hybrid HVDC Breaker (HHB) turns out to be a good combination for MTDC grids, which ensures minimum disturbance to the operation of ac-dc power system during dc faults, enhancing reliability and grid security. In MTDC grid, a dc switchyard is essential at each converter station, which acts as a transition point for various incoming and outgoing feeders. HHB can be designed as an internal equipment of such dc switchyard. The design of such dc switchyard is very important from the operational and cost perspective in achieving the required power system reliability and security. This paper utilizes the modular feature of Hybrid HVDC breaker (HHB) to design a N-feeder dc switchyard with reduced component count. A generalized procedure to develop an electrical layout of N-feeder dc switchyard and its operation are proposed. Operation of a dc switchyard under failure of HHB components is also demonstrated.