Comparative Analysis of Symmetrical-Component Extraction Methods for IEEE 2800-2022-Compliant Negative-Sequence Regulation in VSM-Based Grid-Forming Inverters

Abstract

This paper compares four extraction methods behind an identical interface in a full-order virtual synchronous machine (VSM) grid-forming inverter: the dual second-order generalized integrator with frequency-locked loop (DSOGI-FLL), delayed signal cancellation (DSC), the extended Kalman filter (EKF) and a super-twisting sliding-mode observer (ST-SMO). Simulations cover short-circuit ratios (SCR) of 1.5, 3 and 5, four fault types and three fault profiles at a converged step of 50 microseconds, and are checked against an analytic truth, a negative-sequence reference reconstructed offline, and a step-size study. DSOGI-FLL has the smallest estimation error (median angle error 1.0 degrees against 3.3, 5.2 and 14 degrees for the EKF, DSC and ST-SMO) and the lowest output ripple (median 0.003 pu against 0.016 pu for DSC). Recovery time (median spread 0.01 s) and rotor-angle deviation (at most 2 degrees) are set by the VSM, the fault type and the SCR and not by the extractor. The ST-SMO injection loop oscillates after fault clearing at the gain at which the other methods are stable, so it is run at a lower gain with a nearly inactive injection. Compliance to the IEEE Standard 2800-2022 is assessed on the realized current, because the commanded lead does not determine it.