Optimal short‐circuit current control of the grid‐forming converter during grid fault condition

Abstract

A considerable amount of rotating synchronous machines are being replaced by the increasing capacity of converter-based resources, which has stimulated a demand for gridforming converters (GFCs) for grid supporting. The inertia and frequency responses of GFC are remarkably similar to those of synchronous generator (SG), but the inadequate capability of sourcing short-circuit current of GFCs during grid fault can lead to several serious consequences. The low short-circuit current level fails to trigger protection relays and cannot provide sustained voltage support during the fault or more effectively support the recovery of voltage after fault clearance. The short-term overcurrent capability of GFC can be promoted either from the point of view of the power devices or from the topology of it. The overcurrent capability of converter is hard-earned, so full use of it should be made. This paper proposes an optimal control strategy of short-circuit current of GFC, which can enable the GFC to source the short-circuit current with an optimal angle within the allowable magnitude. A detailed simulation model of the proposed method here is set up in PSCAD/EMTDC. The simulation results show that the proposed method can achieve better voltage supporting results compared with the traditional reactive support control.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

A Review of Current-Limiting Control of Grid-Forming Inverters Under Symmetrical Disturbances

“…However, the PLL can suffer from small-signal or transient instability issues under weak grid conditions [46], [47]. An alternative solution that avoids switching the synchronization methods is to adjust the active and reactive power references based on grid codes [16], [48], [49], which are further tracked by power control loops to achieve the fault current contribution goal [50]. An example based on [7] is given as…”

“…System stability is an essential requirement for both GFM inverter protection and successful disturbance ride-through. Given certain disturbances, numerical methods are widely applied to testify the stability of a single GFM inverter with current limiters [27], [28], [45], power limiters [69], [70], virtual impedance / admittance [31], [61], and hybrid methods [16], [48]. Furthermore, the stability of multiple GFM inverters with different current-limiting methods are illustrated by the numerical methods in [29], [33], [36]- [39], [56]- [58], [71]- [73].…”

Grid-Forming Inverter-based Wind Turbine Generators: Comprehensive Review, Comparative Analysis, and Recommendations

“…15, although the SGFM types stably recover in the post-fault condition with overload mitigation control scheme, transient current of SGFM types during fault reaches 5 pu, which can damage the power converter. Since existing current saturation scheme of GFL control cannot be used for the MGFM types, different current limiting strategies have been developed, such as switching control strategy from grid-forming to grid-following during fault period [40], virtual active power [41], using virtual impedance or admittance in addition to current saturation algorithm [42]- [44], current reference limiting with anti-windup integration [45], current-constrained unified virtual oscillator control [46], and circular current limiter [47]. Most existing current limiting strategies have been developed for the multiloop GFM controls.…”

A Review of Current-Limiting Control of Grid-Forming Inverters Under Symmetrical Disturbances

“…For certain faults or disturbances, numerical methods are widely applied to testify the stability of a single GFM inverter with current limiters [18], [19], [44], power limiters [21], [54], virtual impedance/admittance [27], [65], and hybrid methods [41], [42]. Furthermore, the stability and performance of multiple GFM inverters with different current-limiting methods are illustrated by the numerical methods in [20], [23], [33]- [36], [59]- [61], [74], [75].…”