Grid-forming (GFM) converters are a promising solution to enable large scale integration of renewable energy sources into the power system. However, due to the intrinsic voltage-source behaviour of GFM converters, current limitation during large grid disturbances is challenging. This paper presents a novel limitation strategy that preserves the GFM properties of the converter and at the same time effectively limits the converter current to the desired value. Through the limitation of the converter's internal voltage, stable operation even during faults and in case of large frequency disturbances in the grid is achieved. Experimental results show the effectiveness of the proposed current limitation strategy in case of various grid disturbances.

The aim of this paper is to present a grid-forming (GFM) control strategy with a novel active-power loop (APL) structure facilitating limitation of active power while providing maximum available inertial support. This is achieved by decoupling the synchronization duties of the APL from the inertial support. The latter is provided by calculating the active-power reference through a dedicated inertia-emulation loop (IEL), which is connected in cascade with the APL. The effectiveness of the proposed method is demonstrated through laboratory experiments including frequency transients of varying size and unbalanced operating conditions.

Grid-forming (GFM) converters are a widely-accepted solution for the challenges arising from the decarbonisation of electrical power systems. Ideally, a GFM converter should act as a slow-varying voltage source behind a (tunable) $RL$ impedance to guarantee setpoint tracking and grid support. However, the inherent coupling between active and reactive power greatly limits the selection of the impedance's parameters often leading to the need for additional controllers, for example to provide damping at the synchronous-frequency resonance. This paper proposes a decoupled power controller that combines a complex-power control loop with a virtual admittance to provide freely tunable parameters that provide damping at subsynchronous and synchronous frequency, decoupling of active and reactive power, as well as providing desired behavior over a wide range of frequency. The controller's performance is evaluated and compared to a conventional control approach both analytically and in a laboratory environment.