# Influence of Load Dynamics on Converter-Dominated Isolated Power Systems
## 6 Conclusions  
This paper focused on isolated power systems operating exclusively with converter-based generation, in which a BESS, whose power converter is controlled as a grid-forming unit, is responsible for providing network regulation capabilities. Within that scope, it was intended to analyze the impact of load dynamics on the BESS power converter sizing. For the case in which the network load is modeled only by static models, a BESS power converter capacity complying with the N-1 security criterion is enough to ensure the network dynamic stability. However, converter-interfaced BESSs have a very limited overcurrent capability, which constitutes a major disadvantage when dynamic loads are connected to the grid. Thus, it was also concluded that the presence of IM loads leads to  
Figure 35: WF1 reactive current output and terminal voltage.  
Figure 36: L3 large industrial motor (**left**) and refrigerator type IM loads speeds and terminal voltages.  
negative effects on the network dynamics following large voltage disturbances due to their large reactive power consumption in the moments subsequent to a fault clearance. In this sense, it is necessary to oversize the BESS power converter capacity in order to cope with short-circuit events, aiming to assure IM load recovery in contrast to undervoltage shedding. An extensive sensitivity analysis was performed, providing a clear understanding of how the load model, composition and parametrization affect the oversizing of the BESS power converter capacity.  
Furthermore, it was demonstrated that the FRT requirements currently demanded by the insular grid codes need to be revised in order to facilitate the operating scenarios with 100% penetration levels of converter-based generation in isolated networks with a significative percentage of the IM load composition. For this purpose, a novel FRT control mode was identified and discussed for the CI-RES. The proposed FRT mode is intended to increase the reactive current contribution of these units in the moments subsequent to the fault clearance, which corresponds to the moments where IM loads demand higher reactive currents for recovering their operation. In addition, it was demonstrated that the dynamic modulation of the reference voltage of the grid-forming unit during the post-fault period contributes to a faster re-magnetization of IM loads, which consequently increases their electromagnetic torque, hence contributing to its reacceleration. Therefore, it is concluded that a proper network load characterization by the respective network operators, as well as the adoption of appropriate advanced control functionalities at the power electronic interfaces existing in the converter-based generators, should avoid BESS power converter oversizing for specific applications in isolated systems.  
**Author Contributions:** Preparation of the manuscript was performed by [PERSON], [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by ERDF--European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation--COMPETE 2020 Programme, and by National Funds through the Portuguese funding agency, FCT--_Fundacao para a Ciencia e a Tecnologia_, within project ESGRIDS.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy issues.  
**Conflicts of Interest:** The authors declare no conflict of interest.