## 6 Conclusions  
In this paper, a novel and enhanced distributed secondary control technique is introduced for a standalone DC microgrid comprising multiple distributed energy resources (DERs). The secondary control technique proposed in this paper addresses voltage deviations resulting from the droop control and ensures equitable distribution of average current among the DERs. A fuzzy logic control technique is utilized to enhance the control capability of the proposed secondary control system. The current-sharing error and voltage deviation inputs drive the fuzzy logic system. It generates the secondary control parameter  
Figure 30: Current output measurement of the DC microgrid during the communication time delay; (**a**) Current output for DER 1; (**b**) Current output for DER 2; (**c**) Current output for DER 3; (**d**) Current output for DER 4.  
Figure 29: DC microgrid common bus voltage during the communication time delay.  
as output, which adjusts the current-sharing and voltage weights accordingly. Every DER is equipped with its own fuzzy-based secondary control system, which facilitates communication with other secondary controllers within the MG to implement distributed control characteristics. By employing the Lyapunov stability analysis, the paper also establishes the necessary condition to guarantee the stable operational performance of the proposed secondary control system within the MG. Furthermore, the robustness and effectiveness of the proposed control system in ensuring proper current sharing and voltage restoration are validated through simulation and experimental results under various test cases, such as communication time delay, DER plug-and-play, and resistive and constant power load variation. The results shows that the proposed FDSC outperforms the conventional secondary control technique with a noteworthy 95% reduction in response time for voltage restoration to its nominal value and a 46.4% decrease in response time for optimal current distribution. Hence, applying the proposed control technique in real-world DC MGs offers a seamless solution to address voltage restoration and current sharing challenges.  
Given that communication plays a crucial role in the distributed secondary control system, ensuring the safety of cyber-physical systems heavily relies on cyber security, which has gained significant traction within the control research area. Addressing potential vulnerabilities such as \"False Data Injection\" or \"Replay Attack\" in our presented technique will be considered as a future focus of this research, aiming to safeguard against malicious activities. Future research directions may also involve exploring various converter topologies and considering the integration of hybrid DERs.  
Conceptualization, A.A., O.L. and A.S.; methodology, O.L., A.A. and A.S.; software, O.L., A.A., A.S. and M.B.; validation, A.A., A.S. and L.J.; formal analysis, O.L., A.A. and A.S.; resources, A.S. and L.J.; writing--original draft preparation, O.L., A.S. and A.A.; writing--review and editing, O.L., A.S., M.B. and L.J.; visualization, O.L. and A.S.; supervision, A.S. and L.J.; project administration, A.S.; funding, A.S. and L.J. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
No new data were created or analyzed in this study. Data sharing is not applicable to this article.  
The authors would like to acknowledge the Centre for Power and Energy Systems at the University of KwaZulu-Natal for their administrative and technical support throughout this project.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
MGsMicrogrids  
DERDistributed Energy Resources  
ESTsEnergy Storage Technologies  
DCDirect Current  
ACAlternating Current  
LFLyapunov function  
FDSCFuzzy-Based Distributed Secondary Control  
CPLConstant Power Load