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.

I. Introduction

With increasing penetration of renewables into the power grids, the need for a fault ride through (FRT) capability becomes crucial in the grid codes [1]. FRT refers to the ability of the power-generating modules to remain connected to the grid and maintain stable operation during grid faults [2], thereby ensuring grid stability and reliability; otherwise, it might lead to loss of synchronization (LOS) of the power generators and system eventually collapse [3].