A new design of decentralized biased proportional and integral dual mode controllers for load frequency control of interconnected power systems considering governor deadband (GDB) and generation rate constraint (GRC) non-linearities is presented in this paper. Any optimum controller selected for load frequency control of interconnected power systems should not only stabilize the power system but also reduce the system frequency and tie line power oscillations and settling time of the output responses. Hence, a simple design of biased controllers with proportional and integral modes using an integral square error (ISE) criterion and maximum stability margin (MSM) criterion based on minimum settling time for interconnected power systems are discussed. These controllers are designed and implemented in a two area interconnected thermal power system with GDB and GRC non-linearities. The proposed controller is found to be simple in structure and easy for implementation. The closed loop system was simulated, and the frequency and tie line power deviations resulting from a step load disturbance are presented. Comparison of the performances of the proportional plus integral biased controller and the proposed proportional (P) and integral (I) biased dual mode controllers shows that the system performance is improved significantly with the proposed controllers. Further, it is also shown that the biased dual mode controllers are found to be less sensitive to change, in system parameters. (C) 2006 Elsevier Ltd. All rights reserved.