High voltage direct current(HVDC) systems are a typical nonlinear system, which are also ac- companied by many uncertain factors. It is unable to establish precise mathematical model. At present, PI/PID controllers are widely used in the HVDC systems, and cannot solve nonlinear and uncertainty problems in HVDC systems. This paper focuses on applying the fuzzy control theory in HVDC control system. This paper combines the advantages of easily coming true of the traditional PID controllers with a- daptability and fuzzy modelling of fuzzy contro...