Observer-based power-synchronization control for grid-forming converters

This paper proposes an observer-based power-synchronization control (OPSC) method for grid-forming converters. The method can also be utilized for the starting of synchronous generators. It is analogous to observer-based volts-per-hertz (V/Hz) control of electric machine drives, consisting of state-feedback control and an observer. A linearized model of the closed-loop system is derived, passivity of the mechanical subsystem is studied and tuning recommendations are given. The power tracking performance is assessed and compared to that of reference-feedforward power-synchronization control (RFPSC) with the help of simulations and laboratory experiments using a 12.5-kVA converter. The results show that the proposed control method provides good performance in both weak and strong grids.