###### Abstract  
The growing integration of renewable energy sources, particularly photovoltaic (PV) and wind power, presents challenges such as reduced system inertia and increased susceptibility to inter-area oscillations. These issues, coupled with stricter regulatory demands for grid stability, highlight the urgent need for effective damping solutions. This study proposes a novel method for detecting and mitigating inter-area oscillations using a power oscillation damping (POD) controller enhanced by applying a Fast Fourier Transform (FFT). The controller's parameters are optimized through the Nobel Bat Algorithm (NBA) and fully implemented in DIgSILENT PowerFactory (DSPF). Simulations conducted on the New England IEEE-39 power system model under varying levels of renewable energy penetration demonstrate the model's capability to dynamically detect, mitigate, and deactivate oscillations once stability is achieved. This work addresses emerging regulations requiring oscillation damping systems and offers a framework for certifying POD controllers for real-world implementation, ensuring their adaptability to diverse energy systems and regulatory contexts. inter-area oscillation; power oscillation damping; photovoltaic plant; fast Fourier transform; Nobel bat algorithm; grid stability; DIgSILENT PowerFactory; power plant controller +
Footnote †: journal: Applied sciences  
0000-0001-9399-22000/00000-0000-0000-0000-00000-0000-00000-  
Notable incidents of inter-area oscillations, such as the 1996 Western System Coordinated Council (WSCC) blackout in the United States [5], the 2003 Northeast blackout [6], and the 2016 oscillatory event triggered by a line opening in the French-Spanish interconnection [7], underscore the urgent need for proactive measures to address grid stability challenges. These events, among others, highlight the severity of inter-area oscillations and the need for their early detection and mitigation. Effective damping strategies are increasingly necessary to ensure the stable operation of power systems with a high degree of renewable energy penetration. Several studies have already focused on stability due to the growing concern about low-frequency oscillations in different countries, focusing on the problem of inter-area oscillations. For example, the impact of resonance on inter-area oscillations in the Nordic power system [8; 9], the analysis of inter-area oscillations in the UCTE/CENTREL power system [10; 11], or the improvement of the damping of the inter-area oscillatory mode between Scotland and England [12]. Growing concern has also highlighted the need for effective grid stability measures at the regulatory level, particularly regarding the implementation of power oscillation damping (POD) controllers. At the European level, Commission Regulation (EU) 2016/631 [13] specifies that renewable generators must be capable of damping oscillations when required by the system operator, ensuring grid stability in critical situations. ACER Recommendation 03-2023 Annex 1 [14] provides further guidance on implementing POD functionalities in high-renewable systems, emphasizing the need for generators to mitigate low-frequency oscillations. In Spain, the draft Operation Procedure (PO) 12.2 [15] requires renewable plants, especially type D (plants whose connection point voltage is equal to or greater than 110 kV or whose maximum power exceeds 50 MW), to have a POD controller capable of damping inter-area oscillations in the range of 0.1 Hz to 1.0 Hz, ensuring integration into the national grid. Additionally, the importance of POD controllers is reinforced by the POD Controller Implementation Guide [16], which outlines the steps and requirements for their implementation, highlighting their critical role in stabilizing the grid and supporting higher renewable energy penetration.