In this paper, we proposed an effective method to design the power system stabilizers (PSS). The design of a PSS based on Grey Fuzzy PID Control (PSS+GFPIDC) can be formulated as an optimal linear regulator control problem; The grey PID type fuzzy controller (GFPIDC) designed in this paper, can predict the future output values of the system accurately. However, the forecasting step-size of the grey controller determines the forecasting value. When the step-size of the grey controller is large, it will cause over compensation, resulting in a slow system response. Conversely, a smaller step-size will make the system respond faster but cause larger overshoots. The value of the forecasting step-size is optimized according to the values of error and the derivative of the error. Moreover, the output of the grey controller is updated using the prediction error for better controller performance. An on-line rule tuning grey prediction fuzzy control system is also presented in this paper, which contains the advantage of the grey prediction, fuzzy theory and the on-line tuning algorithm. The on-line rule tuning grey prediction fuzzy control system structure is constructed so that the rise time and the overshoot of the controlled system can be maintained simultaneously.

PID Controller, Power System Stabilizer (PSS), On-line rule tuning, Grey Prediction, Grey Fuzzy PID Control