In HVDC/AC interconnected system, commutation failure caused by AC system faults at the inverter side will adversely bring complicated transient characteristics about AC system, which has an influence on existing protection. This paper analyzes the adaptation of phase selector based on fault component in HVDC/AC system. Firstly, three phase switching function of commutation bridge is discussed, which is affected by both AC fault time and commutation failure times in a cycle after fault. Then, a precise method to calculate the post fault DC current based on control strategy is provided. On this basis, transient characteristics of inverter-side AC current and its influence on phase selector based on fault component is analyzed. It shows that commutation failure changes the switching function and generates current changes in non-fault phase, which may lead to malfunction of phase selector. Finally, PSCAD/EMTDC simulations is provided to verify the correctness of theoretical analysis.

commutation failure, switching function, transient characteristics, fault component, phase selector.