A Novel Converter Topology for Solving Commutation Failure in LCC-HVDC Systems

To solve the problem of commutation failure of the LCC converter, a novel topology of controllable line commutated converter (CLCC) with controllable turn-off capability was proposed. Based on the design concept of the DC circuit breaker (DCCB), this topology adopts a mixed connection scheme of semi-controlled devices and fully controlled devices (IGCTs) which can effectively resist commutation failure by applying the proposed control strategy. Through analysis and validation in time-domain simulation, the CLCC converter not only had the same system operation performance with LCC converter, but also completely solved the commutation failure (CF) problem. The parameter design method is deemed reasonable, and the stresses on the components of the converter bridge arm are within the allowable design range.