FRT Capability of Grid-Forming Power Converters: An Antiwindup Scheme

Fault ride-through requirements by grid codes necessitate grid-forming (GFM) power converters to operate stably during large grid disturbances, such as voltage dips, voltage phase jumps, and rapid frequency changes. Nevertheless, the limited overcurrent capability of power converters deteriorates the transient synchronization stability during faults. To this end, this article suggests an anti wind-up (AW) scheme from the hard current limiter block toward the active power loops (APL). In this way, the outer APL can recognize that the converter is in the saturated mode and that reference power exceeds the power limit injection that grid conditions allow; and therefore, the control effort should be modified in accordance with the allowable capacity. The proposed mechanism is first explained by presenting phase-portrait analysis through a nonlinear complex phasor model of the system; it is then shown a good correlation between the phasor domain and time domain findings. Finally, the effectiveness of the proposed method is shown through EMT simulations and experimental results.