Prevent commutation failure and maintain voltage stability are two important issues for high voltage direct current(HVDC)receiving end power grid. In order to reduce the threat of commutation failure

the actual HVDC control system is usually equipped with the module of commutation failure prediction. Predictive control will reduce the inverter trigger angle in the process of disturbance

and then affect the reactive power and the voltage stability of the receiving end power grid. Based on the control system used in the actual project

the simulation model of ultra-high voltage direct current(UHVDC)is established. Considering the function commutation failure module

the characteristics of reactive power nonlinear trajectory of inverter station is revealed. The influence of parameters in the predictive module on the reactive power characteristic is analyzed. On this basis

the parameter optimization scheme is put forward for enhancing the reactive power characteristic of large disturbances in inverter station. Simulation results obtained from the receiving end power grid of UHVDC verify that voltage stability of the receiving end power grid can be significantly enhanced.