Mechanism and application of spatial-temporal characteristics of regional frequency in low inertia power system

• The TAFR model is established based on the equation of power flow and rotor motion. • The closed-form solution of all components is obtained based on closed-loop equivalent substitution and modal analysis. • The mechanism of spatial–temporal characteristics of the system frequency are analyzed on the basis of closed-form solution. • A frequency-based protection correction strategy is proposed on the basis of the spatial–temporal characteristics. It’s a trend for high-penetration renewable energy to participate in frequency regulation in low inertia power system, however the fluctuation of weather makes renewable energy variable in its frequency support capacity, resulting in an obvious spatial–temporal characteristics of node frequency after power disturbance in power grids. However, it is difficult for the traditional center of inertia (COI) based theory to analyze the mechanism, let alone the adaptively improved frequency control strategy. Therefore, the mechanism of the spatial–temporal characteristics of grid node frequency is investigated by modeling and analytical analyses of the frequency response (FR) in different areas, including both the frequency deviation (FD) and the rate of change of frequency (ROCOF). Specifically, an equivalent two areas FR (TAFR) model is first established. By decomposing the closed-loop feedback and the equivalent substitution, the high-order model is equivalent to a combination of typical low-order systems, then the modal analysis method is adopted to obtain the closed-form solution (CFS), which addresses the problem of the higher-order system solution. And then the method is expanded to n -area system. Furthermore, through the mathematical analyses of the solution, the spatial–temporal characteristics of the FD and ROCOF in different areas are obtained. Accordingly, a frequency-based protection correction strategy is proposed to adapt to the new characteristic of regional frequency. Finally, the simulation verifies the accuracy of the TAFR model and its CFS, and the effectiveness of the proposed protection correction strategy.