A type of constant current control system which is devised with PI-D structure is designed in this paper

and the parameters optimization method is also put forward. First

a differentiator is added to the feedback path of the traditional PI controller

thus constituting a controller with PI-D structure. Then

for-mulate the transfer function expression which contains the controller parameters of the HVDC system

and draw the Bode diagrams of the system as the control parameters vary. According to the variation of the Bode diagram

the most appropriate parameters can be found. According to the above-mentioned method

a constant current controller with PI-D structure is designed for the CIGRE HVDC benchmark model. To validate the performance of the designed controller

a traditional PI-D controller is also designed as the contrast.The simulation test demonstrates that

compared with the traditional PI and PID controller

the PI-D controller has better time-domain response characteristic and anti-interference ability.