Development of sigmoid based nonlinear controllers in a PID framework for load frequency stabilization

The present work proposes Sigmoid-transformed PID (STPID), TanSig PID (TSPID), and TanSig PI-TanSig PD (TSPI-TSPD) controllers, resulting in novel structures for frequency stabilization of a power system based on nonlinear transformation of the area control error (ACE). This is achieved by employing hyperbolic tangent functions with tunable slope and amplitude parameters to transform the error signal nonlinearly. The evolution of such new architectures has been inspired by the structural framework of a Fuzzy PID (FPID) controller, where the fuzzy block output is a nonlinear function of the error and its derivative. The efficacy of proposed controllers has been validated on a few power system test models with encouraging results. The TSPID controller has demonstrated highly satisfying behavior in the presence of measurement noise. Furthermore, integrating an anti-windup mechanism has resulted in improved outcomes. The stability analysis has been carried out using Bode plots. OPAL-RT platform has been used to conduct real-time simulation. A new metaheuristic technique called the Giza Pyramids Construction (GzPC) algorithm is used to tune the controller parameters.