The LCC-HVDC commutation failure caused by AC power network fault affects the operation of directional protection based on power-frequency component variation for AC transmission lines. A hybrid multi-infeed HVDC system model consisted of a VSC-HVDC system and a LCC-HVDC system is set up, compared with a AC/DC system of a single LCC-HVDC system fed into the same AC grid. Combined with the characteristic of the analysis of power-frequency component variation based on the principle of directional protection, the performance of LCC-HVDC equivalent impedance of power-frequency component variation is quantitatively analyzed under the same commutation failure in LCC-HVDC system of this two different transmission structures. The simulations of two different structures for the same commutation failure of HVDC in identical fault simulated by PSCAD/EMTDC testify the accuracy and validity of the theory analysis. It indicates that the hybrid multi-infeed HVDC system can improve the impact of directional protection based on power-frequency component variation caused by the LCC-HVDC commutation failure and provides the theoretical basis for the power network planning.