# Model Predictive Control of Grid Forming Converters with Enhanced Power Quality
## 5 Conclusions  
In this work, a proposal of an improved FCS-MPC is presented, and the suitability of three different frequency control approaches has been investigated. The frequency control algorithms with the improved scheme introduced new FCS-MPC regulators for grid forming converters. The primary objective of the CF is to predict the voltage, while the secondary objective is to improve the power quality for enhancement purposes. In order to have similar characteristics as the conventional linear controllers, FCS-MPC should control the switching frequency and reshape the spectrum at desired values. One advantage is to reduce the losses by reducing the average switching frequency, where the new CFs do not introduce a high computational burden. Another advantage is to control system, which uses only one-step prediction. In this respect, the steady-state performance of the system becomes comparable with some recent proposed FCS-MPCs, which achieve good power quality using longer horizon or multi-step prediction. Besides, this work has shown that the frequency can be concentrated, while the feature of the fast dynamic response is retained. Some challenges have been solved during this work-study, and there were as follows:  
* Weight factors tuning, which affects the performance of the power converter. This challenge solved by defining the importance of each objective in multi-objective CF.
* Another challenge was to include the most suitable frequency control objectives without using a modulator and send the optimized actuation based on the error evaluated by the CF. This challenge has been solved by investigating the performance of each frequency control scheme combined with the improved FCS-MPC.
* High-frequency sampling, which is solved by concentrating the switching frequency at a relatively lower frequency. That allowed the standard setups to handling this kind of controllers.  
In the end, this work showed that the proposed derivative, FCS-MPC based scheme could improve any approach introduced so far for controlling the switching frequency. Periodic control achieved promising results in terms of power quality and fixed switching behaviour. Moreover, periodic control has a simple and easy implementation for further consideration in the grid-forming applications. The proposed cost function is applicable for complicated systems such as the matrix or neutral point clamped converters. The idea behind using VSC is to simply illustrate the new schemes and verify the frequency control methods and providing some comparisons. As future work, researchers are seeking new techniques to eliminate the weighting factors or using intelligent technologies in order to calculate the weighting factors online resulting in much more flexibility.  
Conceptualization, M.A., P.D. and F.B.; methodology, M.A.; software, M.A., A.A.; validation, M.A.; formal analysis, M.A. and P.D.; investigation, M.A., P.M.; resources, P.D. and F.B.; data curation, M.A.; writing--original draft preparation, M.A.; writing--review and editing, M.A., P.D., P.M. and F.B.; visualization, M.A.; supervision, P.D. and F.B.; project administration, M.A.; funding acquisition, P.D. and F.B. All authors have read and agreed to the published version of the manuscript.  
This research is supported by Arab Academy for Science, Technology and Maritime Transport and Department of Energy Technology at Aalborg University.  
The authors declare no conflict of interest.