Frequency Stability Evaluation Based on Conservative Piecewise-Linearized Frequency Nadir Model in South Korea. - Yongbeom Son; Minhyeok Chang; Chiwon Seo; Sungwoo Kang; Yonggu Ha; Jongan Kim; Myunghwan Choi; Minhan Yoon; Gilsoo Jang (IEEE Access, 2025)