This paper discusses the impact of HVDC on

Power System Stability and proposes a new control mechanism

based on Fuzzy set theory to augment dynamic performance of

a multi-machine power system. To have good damping

characteristics over a wide range of operating conditions,

deviations in speed and acceleration of the machines are chosen

as the input signals to the fuzzy controller. These input signals

are first characterized by a set of linguistic variables using fuzzy

set notations .The fuzzy relation matrix allows a set of fuzzy

logic operations that are performed on controller inputs to

obtain the desired output. The effectiveness of the proposed

controller is demonstrated by a multi-machine system example.

The performance of this fuzzy controller, in comparison to the

conventional fixed gain controller, demonstrates the efficacy of

this new fuzzy PID controller.

Index Terms—HVDC, Eliminated variable