A new design of dual mode Type-II fuzzy logic load frequency controller for interconnected power systems with parallel AC–DC tie-lines and capacitor energy storage unit

• In an interconnected power system LFC plays a crucial role to maintain the frequency and tie-line flows.
• A new approach of dual mode Type-II FLC is proposed in this paper.
• Maintaining a nominal deviation of over shoot and under shoot.
• AC–DC tie line and CES unit is incorporated with this model.
• Simulation results show the robustness of the proposed control strategy.

A new design of dual mode Type-II fuzzy logic load frequency controller (DMT-IIFLC) for interconnected power systems with parallel AC–DC tie-lines and capacitor energy storage unit (CES) is proposed 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. In general proportional plus integral controllers are used for loadfrequency control but it does not eliminate the conflict between the static and dynamic accuracy. This dispute may be broken up by using the principle of T-IIFLC to utilize expert knowledge and being adaptive in nature. The dual-mode concept is incorporated in the proposed controller to improve the system performance. A DC link is connected in parallel with AC tie-line to stabilize the frequency of oscillations. In summation, the CES unit is found to be advantageous for secondary control in the power system and keeps the power quality with the distributed power resources. The CES, which are not aged to the frequent charging and discharging, has been a quick response and outstanding function during overload conditions. The system performance of the proposed controller have improved significantly when compared with PI and T-IFLC. It is also found to be less sensitive to the changes in the system parameters and also robust under different operating modes of the system.