T–S Fuzzy-Based Load Frequency Control of Multiarea Power System With Hybrid Delays: Performance Analysis and Improvement

Load frequency control (LFC) is crucial for ensuring the frequency stability of power system, and its control performance is often affected by nonlinearities in devices and multisource-induced hybrid delays in control signal transmission networks. This article investigates the LFC performance analysis and improvement of power systems under the nonlinearities and hybrid delays. First, the nonlinear part is approximated by a Takagi–Sugeno (T–S) fuzzy model and the hybrid delay is divided into two regions, thus establishing a T–S fuzzy LFC model with hybrid delays. Then, based on switched system theory, a delay-dependent weighted $H_\infty$ performance analysis criterion for LFC system is proposed, giving the necessary conditions to achieve a certain robustness of the system against disturbances. On this basis, a controller design method is proposed to ensure the system have the optimal level of disturbance rejection under the designed controller. Finally, case studies based on single-area and three-area LFC demonstrate that, compared with previous methods, the proposed method can obtain a larger allowable upper bound of delays and better $H_\infty$ performance estimation. Based on this, the designed controller enhances the robust performance of LFC, thereby ensuring the stable operation of power systems under nonlinearities and hybrid delays.