Cascaded fractional order automatic generation control of a PV-reheat thermal power system under a comprehensive nonlinearity effect and cyber-attack

The integration of renewable energy systems into the existing power grid has become a global necessity. While there are numerous advantages to this integration, it also presents challenges such as oscillations in system frequency and tie-line power. These issues can lead to instability and undesirable situations within the power system. To ensure a consistent and reliable supply of high-quality electrical power to consumers, a control system is essential. In recent years, cascaded controllers, known for their increased flexibility and degree of freedom compared to non-cascaded controllers, have gained popularity in the literature. In this study, we aim to examine the performance of cascaded fractional and integer order TI-TD and PI-PD controllers in comparison with non-cascaded PID and TID controllers for a challenging stability and robustness assessment. Our focus is on a two-area PV-reheat thermal power system. By conducting comprehensive tests, we aim to gain insights into the effectiveness of these controller types within this context. To ensure optimal controller responses, the designed controllers are optimized using the Mayfly algorithm, with a focus on minimizing the integral of the time-weighted absolute error performance index. The performance tests conducted in this study cover various aspects, including time domain analysis, robustness, random load changes, the impact of progressive nonlinearities, and cyber-attack (C-A) scenarios. The power system under examination incorporates several nonlinear components, namely governor dead band, generation rate constraints, boiler dynamics, and time delay. Additionally, two C-A models, namely resonance attack (ResA) and random attack, are applied to the controller systems. Unlike conventional robustness and C-A tests found in existing literature, this study goes further by measuring the response of the proposed controller to high parameter changes (uncertainty) and conducting a quantitative analysis of its resilience against C-A scenarios. The aim is to assess the controller’s ability to withstand significant variations in system parameters and its effectiveness in dealing with cyber-attacks. The simulation results demonstrate the superior performance of the optimized and cascaded controllers, particularly the TI-TD controller. These controllers exhibit improved performance compared to other controllers reported in the literature. The findings validate the effectiveness of the proposed controllers and highlight their advantages in terms of system stability, response time, and overall control quality.