Coordination and optimum design of hybrid circuit breakers for operation in multi-terminal HVDC systems

The protection of multi-terminal HVDC systems by means of hybrid circuit breakers is a challenge because without coordination between the circuit breakers some unfaulted sections of the system could be disconnected. This paper proposes a new hybrid circuit breaker operation that accounts for the response of all circuit breakers installed to protect a multi-terminal HVDC system in order to coordinate them and avoid a false operation. The paper also includes the optimum selection of the main circuit breaker parameters installed to protect a multi-terminal HVDC system. The application of the procedure, based on a parallel MATLAB-EMTP application previously presented by the authors, shows that the resulting ranges of parameter values that optimize circuit breaker operations when the goal is to protect a multi-terminal HVDC system can be different from those obtained for a two-terminal system.