Transient Frequency Indicator Estimation Incorporating Fault Ride-Through Recovery Dynamics of Power Electronic Devices

To facilitate the transition to green energy and enable long-distance cross-regional power transmission, the global penetration of renewable energy generators (REGs) and high-voltage direct current (HVDC) systems in power grids is rapidly increasing. The displacement of conventional synchronous generators by REGs reduces system inertia. Concurrently, the dynamic recovery characteristics of REGs' post fault ride-through (FRT) and the active power deficits resulting from the commutation failure(CF) recovery processes in HVDC systems pose significant additional challenges to power system frequency stability. To quantify the impact of short circuit faults on frequency stability in power systems dominated by electronic devices, this paper proposes a novel transient frequency indicator estimation method that explicitly incorporates the FRT recovery dynamics of power electronic devices. By evaluating four critical quasi-steady-state sections: corresponding to fault inception, fault clearing, FRT recovery completion of HVDC systems, and the FIVDR voltage recovery instant, we offer rapid and accurate quantification of two critical frequency stability metrics: the rate of change of frequency (RoCoF) and the frequency nadir. To validate the proposed method, case studies are conducted using a modified CSEE-VS test system. The results clearly demonstrate the critical impact of the FRT recovery dynamics of power electronic devices on the frequency stability of the power system.