Enhancing frequency support utilizing smart transformers in RES-dominated power systems integrated with fractional order controller

• A frequency regulation framework is implemented that leverages the flexibility of smart transformers to shape VDL consumption and provide primary frequency response. • A FOPID controller is employed in the SFR loop due to its superior dynamic performance and enhanced flexibility in regulating system frequency. • Lichtenberg Algorithm (LA) is used to tune secondary controllers. • Convergence characteristics reveal that the LA attains significantly faster convergence. • Sensitivity analysis validates the robustness of the proposed frequency regulation approach. As renewable energy sources increasingly replace traditional generators in modern power grids, the availability of online frequency regulation resources declines, thereby weakening the system's overall frequency control capabilities. Although various inertia emulation techniques are available in the literature, managing load consumption is considered one of the more attractive solutions. With an appropriate mechanism, efficiently shaping load consumption can enable it to act as a power reserve during over- or under-frequency events. To this end, this article investigates the flexibility of Smart Transformers (STs), which can shape voltage-dependent loads (VDL) at the distribution level to provide primary frequency response. In addition, due to its superior control performance, the Fractional-Order Proportional-Integral-Derivative (FOPID) controller is implemented within the secondary control layer of interconnected balancing areas, and its performance is compared with PID and Tilt-Integral Second-Order Double-Derivative (TIDD²) controllers. The parameters of all the controllers are selected using a novel metaheuristic-based optimization called the Lichtenberg Algorithm (LA). To justify the superiority of the LA-based technique, its convergence characteristics are compared against various state-of-art algorithms. Case studies reveal the improved dynamic performance due to the participation of ST in the frequency regulation process, which effectively manages the load consumption, thereby contributing to grid frequency stabilization. It is observed that the primary responses from the STs and governors, along with the FOPID controllers, can significantly enhance system performance by mitigating oscillations and peak deviations. Later, sensitivity analysis demonstrates that the proposed framework under diverse grid uncertainties exhibits remarkable robustness and superior performance.