# On Transient Stability Problems in DC Microgrids
## 1 Introduction
[22] analyzed the stability of DC microgrids with constant power loads (CPLs) under distributed control strategies, deriving sufficient conditions for stability. Nevertheless, their study was limited to specific control methods and load types, lacking a more comprehensive analysis. [PERSON] and [PERSON] [23] developed a reduced-order model for DC microgrids and studied its stability using bifurcation theory, providing insights into system dynamics. However, the simplified model may not capture all practical aspects, requiring  
Figure 1: Schematic of DC microgrids. further experimental validation. [PERSON] et al. [24] conducted a comprehensive review of control strategies for DC microgrids and multi-microgrid clusters, highlighting stability challenges and trends. However, their review mainly focused on summarizing existing methods, not proposing novel solutions. [PERSON] et al. [25] proposed an interconnection and damping assignment passivity-based controller for a DC-DC boost converter with CPL, demonstrating improved stability compared to conventional controllers. Nonetheless, the performance of the proposed controller under various operating scenarios needs further investigation. [PERSON] et al. [26] introduced an adaptive droop control scheme to balance the state of charge of energy storage systems in DC microgrids while maintaining stability. Still, the impact of the adaptive droop control on overall system stability requires more in-depth analysis. [PERSON] et al. [27] provided a comprehensive review of DC microgrid architectures, control strategies, protection schemes, power quality, and standardization aspects, offering a holistic view of the technology. However, their primary focus was not on stability analysis. Similarly, [PERSON] et al. [28] reviewed fault detection, isolation, and protection strategies for DC microgrids, identifying challenges and future research directions, but did not thoroughly address stability issues. Despite the valuable contributions of existing literature, there remains a need for a comprehensive analysis comparing the transient stability of DC microgrids under different power control strategies. This study aims to bridge this gap by providing an in-depth examination of transient stability under two primary power control methods: Proportional-integral (PI) control and droop control. By deriving the equilibrium points, power-transfer limitations, and stability conditions for both control strategies, this article presents a generalized framework for understanding and comparing their impact on transient stability. The theoretical analysis is further validated through experimental verifications, emphasizing the practical relevance of the findings. Major contributions of this article are summarized as  
1. [label=(0)]
2. Disclose transient stability problems in DC microgrids;
3. Derive the equilibrium points, power-transfer limitations, and stable conditions of PI-power-controlled and droop-controlled DC generators;
4. Conclude that droop-controlled DC generators feature better transient stability. The rest of this article is organized as follows. Section 2 describes the fundamentals of transient stability problems in AC and DC microgrids. Section 3 analyzes the effect of control on the transient stability. Section 4 provides experimental results for verifications. Section 5 concludes this article.