Fuzzy Type-2 Controller Design for Small-Signal Stability Considering Time Latencies and Uncertainties in PMU Measurements

Wide-area damping controllers are generally provided in a large network to prevent small-signal oscillations. These controllers utilize remote measurements provided by synchrophasors. However, these communicated measurements are delayed and uncertain. Type-2 fuzzy provides higher order approximation of uncertainty and is able to provide solutions for real-world problems in more a reliable manner. Therefore, in this paper, a wide-area damping controller based on interval type-2 fuzzy system is designed. Proposed controllers not only consider time latencies of communicated signals but also eliminate various measurement uncertainties and noise by modeling foot of uncertainty (FOU). First, eigenvalue analysis of the system is performed to identify interarea modes responsible for small-signal instability. To nullify this instability, a control scheme is proposed. In proposed control scheme, participation factors are utilized to select suitable controller location. However, feedback signals are chosen through controllability indexes. Later, type-1 and type-2 controllers are designed by changing membership functions. Performance of type-2 controllers is checked for different FOUs. Furthermore, type-1 and type-2 controllers are compared, in terms of settling time, peak overshoot, and damping factor. Effectiveness of proposed control scheme and controllers are successfully tested on two-area four-machine and five-area sixteen-machine systems.