# Modeling and Simulation of Autonomous DC Microgrid with Variable Droop Controller
## 5 Conclusions  
In this study, a decentralized voltage droop control strategy for DC microgrids in autonomous operation has been explored. The limitations of the fixed droop control is addressed by introducing a dynamic droop resistor that adapts in real time to load transients. The proposed variable droop control strategy effectively mitigates sharp voltage fluctuations, significantly improving voltage regulation and ensuring higher power quality. Although both fixed and variable droop controllers can achieve satisfactory current sharing, the variable droop approach offers distinct advantages in terms of stabilizing the DC bus voltage under varying load conditions. In situations when demand profiles are variable or unpredictable, this improved voltage stability adds to the overall dependability and effectiveness of DC microgrids. The key assumptions made in the proposed model are as follows:  
Figure 11: Variation in droop resistance with load current.  
Figure 12: Illustration of the variable droop coefficient.  
Figure 10: DC bus voltage for a load transient of 1.5 kW with variable droop (zoomed from Figure 7).  
Approximating the nonlinear model of the DC microgrid system as a linearized model.
* 2 Replacing the communication from the secondary level control to the droop controller as manual input.
* 3 The generation is assumed stable and the renewable energy generation dynamics is not considered and emphasis is laid on the load power dynamics and the application of droop control strategies for the bus voltage stability problem.  
Further studies could also explore the integration of advanced control techniques, such as model predictive control or machine learning-based approaches, to improve real-time performance and resilience under diverse operating conditions. Future extension of this work is possible by realizing a hybrid microgrid in which the DC- or AC-based devices can be connected directly to the network with limited interface elements, decreasing the conversion losses and cost. The need for the synchronization of generation units and storage units is eliminated since they are directly connected to either the DC or AC network. Developing efficient coordinate control strategies for power flow management between the subgrids is a potential area of research. In cases where the AC microgrid is grid connected and the DC loads are managed by the DC subgrid, this control strategy could be adapted with sufficient modifications considering the voltage range and power level of the DC bus. The challenges might include the design of power converters, filter components, droop coefficients, communication for secondary level control, etc.  
Conceptualization, R.P.N. and K.P.; methodology, R.P.N. and K.P.; software, R.P.N. and K.P.; formal analysis, K.P.; investigation, R.P.N. and K.P.; writing--original draft preparation, R.P.N.; writing--review and editing, K.P.; supervision, K.P. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors declare no conflicts of interest.