Cross-timescale dynamic interaction issues in power-electronized power systems

The construction of the New-type Power System, by accelerating the large-scale integration of renewable energy generation (such as wind and solar PV) and HVDC transmission, will provide a solid foundation for the clean and low-carbon transition of the economy and society. In systems with high penetration of renewables and dense HVDC, the dominance of synchronous generators is being replaced by power electronic devices, leading to system characteristics defined by power electronics. This transformation of the primary physical components introduces new challenges related to multi-timescale stability in practical engineering. Influenced by both the multi-scale cascaded control structures of power electronic equipment and the nonlinear correlations across these scales, interactions between multi-timescale dynamics exhibit novel cross-scale characteristics. These features fundamentally challenge traditional definitions, classifications, analytical methods, and control paradigms for power system stability, thereby threatening secure system operation. This paper begins by examining the structural and nonlinear characteristics of multi-scale cascaded control in power electronic devices. Combined with numerical simulations, it elucidates the problem of cross-scale dynamic interactions in power-electronized systems. Subsequently, it outlines the challenges and methodologies for analyzing these interactions. The study further provides a preliminary exploration of the multi-scale nonlinear response characteristics of network power under amplitude-frequency time-varying internal electromotive force excitation, analyzing the coupling paths and mechanisms of cross-timescale interactions in power-electronized systems under the influence of cascaded control structures and nonlinear dynamics.