An adaptive fuzzy logic controller for AC-DC power systems

The paper presents a new approach to the design of a supplementary stabilizing controller for a HVDC transmission link using fuzzy logic. The fuzzy controller relates significant and observable variables like speed and its rate of the generator speed and its rate of change of the generator to a control signal for the rectifier current regulator loop using fuzzy membership functions. These variables evaluate the control rules using the compositional rules of inference. The fuzzy controller is equivalent to a nonlinear PI controller, whose gains are adapted depending on the error and its rate of change. The effectiveness of the proposed controller is demonstrated by simulation studies on a DC transmission link connected to a weak AC power system and subjected to transient disturbances.