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

LFC (Load frequency control) in power systems is very important to supply reliable electric power with good quality. In general, proportional PI (plus integral) controller is used for the LFC, which is incapable of obtaining good dynamic performance for a wide range of operating conditions. Type-I fuzzy logic controller (T-I FLC) is a sophisticated technique to use, but the designing of membership functions and control rules is an important function.. To achieve satisfactory membership function and control rules, a designer's experience is necessary. This conflict may be checked up byapplying the principle of Type-II fuzzy logic controller (T-II FLC) to use expert knowledge and being adaptive in nature. The dual-mode concept is incorporated in the proposed controller to improve the system performance. In this work, SMES (superconducting magnetic energy storage) unit and parallel alternating current - direct current (AC-DC) tie-lines are included with base model to study their performance under different operating conditions. The simulation results were analyzed using MATLAB 2014, proving that the superior performance of the proposed controller provides very good transient and steady state response when compared to PI and T-I FLC under different operating conditions and parameter variations.