Effect of fractional-order controller on automatic generation control of a multi-area thermal system

A concept of fractional order (FO) control has received an increasing interest recently in the control areas. This paper investigates the effect of a fractional-order Proportional plus Integral plus Derivative (FOPID) controller in automatic generation control (AGC) of interconnected two unequal and three unequal area thermal systems considering appropriate generation rate constraint (GRC). Integral square error (ISE) criteria have been used as performance index to design the optimal controller keeping frequency bias setting fixed at frequency response characteristics. The performance of FOPID controller is investigated and compared with several integer-order (10) classical controllers such as integral (I), Proportional plus Integral (PI), Proportional plus Integral plus Derivative (PID). The optimum value for several parameters is obtained using classical approach minimising cost function J. Studies reveal that FOPID controller having five tuning knobs are quite robust and provide superior dynamic performances in terms of settling time and reduction in oscillation of frequency and tie line power deviation dynamic response as compared to all the conventional 10 controllers. System performances are examined with 1% step load perturbation in ureal.