Citation: Ahmed, K.; Hussain, I.; Seyedmahmoudian, M.; Stojcevski, A.; Mekhilef, S. Voltage Stability and Power Sharing Control of Distributed Generation Units in DC Microgrids. Energies 2023, 16, 7038. https:// doi.org/10.3390/en16207038 Academic Editors: Sreedhar Madichetty and Abdelkader El Kamel Received: 16 June 2023 Revised: 3 October 2023 Accepted: 6 October 2023 Published: 11 October 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). energies Article Voltage Stability and Power Sharing Control of Distributed Generation Units in DC Microgrids Kafeel Ahmed 1, * , Irfan Hussain 1,2 , Mehdi Seyedmahmoudian 1 , Alex Stojcevski 1, * and Saad Mekhilef 1,2,3 1 School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Hawthorn, VIC 3122, Australia; ipanhwar@swin.edu.au (I.H.); mseyedmahmoudian@swin.edu.au (M.S.); smekhilef@swin.edu.au (S.M.) 2 Power Electronics and Renewable Energy Research Laboratory, Department of Electrical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia 3 Electrical Engineering Department, College of Engineering, University of Ha’il, Ha’il 81481, Saudi Arabia * Correspondence: kahmed@swin.edu.au (K.A.); astojcevski@swin.edu.au (A.S.) Abstract: Advancements in power conversion efficiency and the growing prevalence of DC loads worldwide have underscored the importance of DC microgrids in modern energy systems. Address- ing the challenges of power-sharing and voltage stability in these DC microgrids has been a prominent research focus. Sliding mode control (SMC) has demonstrated remarkable performance in various power electronic converter applications. This paper proposes the integration of universal droop con- trol (UDC) with SMC to facilitate distributed energy resource interfacing and power-sharing control in DC microgrids. Compared to traditional Proportional-Integral (PI) control, the proposed control approach exhibits superior dynamic response characteristics. The UDC is strategically incorporated prior to the SMC and establishes limits on voltage variation and maximum power drawn from the DC–DC converters within the microgrid. A dynamic model of the DC–DC converter is developed as the initial stage, focusing on voltage regulation at the DC link through nonlinear control laws tailored for Distributed Generation (DG)-based converters. The UDC ensures voltage stability in the DC microgrid by imposing predetermined power constraints on the DGs. Comparative evaluations, involving different load scenarios, have been conducted to assess the performance of the proposed UDC-based SMC control in comparison to the PI control-based system. The results demonstrate the superior efficiency of the UDC-based SMC control in handling dynamic load changes. Furthermore, a practical test of the proposed controller has been conducted using a hardware prototype of a DC microgrid. Keywords: DC microgrid; distributed generation; sliding mode control; universal droop control; voltage stability; power sharing 1. Introduction The concept of microgrid (MG) has evolved from a simple network of distributed generation (DG) to a sophisticated, multi-mode-operated network that is automated, self- tuning, capable of trading with the main grid, and capable of isolating faulty components of the system [1]. Direct current (DC) MGs offer several advantages over alternating current (AC) MGs, primarily due to the reduced need for energy conversion systems [2,3]. Most DG sources in MGs, such as fuel cells, photovoltaics, and energy storage, inherently operate on DC, while most load types are also being designed to operate on DC supply, and their dominance is expected to increase in the future [4,5]. The use of DC in MGs helps to minimize the number of conversion steps, thereby reducing energy losses associated with power electronic conversion [6]. Furthermore, high-voltage direct current (HVDC) tech- nology is being explored for efficient interconnection of remotely located MGs and power systems operating at different operational standards [7]. However, the wider deployment Energies 2023, 16, 7038. https://doi.org/10.3390/en16207038 https://www.mdpi.com/journal/energies