DC Microgrids – Part I: A Review of Control Strategies and Stabilization Techniques

DC Microgrids – Part I: A Review of Control Strategies and Stabilization Techniques

2016 | Dragicevic, Tomislav; Lu, Xiaonan; Quintero, Juan Carlos Vasquez; Guerrero, Josep M.
This paper presents a review of control strategies, stability analysis, and stabilization techniques for DC microgrids (MGs). The control of DC MGs is systematically classified into local and coordinated control levels based on their respective functionalities. Local control relies on local measurements, while coordinated control requires communication between units. Three basic coordinated control strategies are distinguished: decentralized, centralized, and distributed control. Decentralized control is an extension of local control, while centralized and distributed control rely on digital communication technologies. The paper reviews various approaches to using these strategies to achieve different control objectives. It also discusses the dynamics and stability of DC MGs, highlighting that tightly regulated point-of-load (POL) converters can reduce system stability margins by introducing negative impedance, which may cause oscillations with lightly damped power supply input filters. The stability of the system is defined by the relationship between source and load impedances, referred to as the minor loop gain. Several prominent specifications for the minor loop gain are reviewed. Active stabilization techniques are also presented. The paper concludes that distributed control can achieve information awareness comparable to centralized control, enabling objectives such as output current sharing, voltage restoration, and global efficiency enhancement. However, distributed control has limitations in analytical performance analysis, especially in non-ideal environments. The paper also discusses the dynamics of regulated power supplies, emphasizing the role of line filters and the impact of POL converters on system stability. The paper concludes that the stability of DC MGs is crucial for safe and reliable operation, and that impedance-based analysis and stabilization techniques are essential for ensuring system stability.This paper presents a review of control strategies, stability analysis, and stabilization techniques for DC microgrids (MGs). The control of DC MGs is systematically classified into local and coordinated control levels based on their respective functionalities. Local control relies on local measurements, while coordinated control requires communication between units. Three basic coordinated control strategies are distinguished: decentralized, centralized, and distributed control. Decentralized control is an extension of local control, while centralized and distributed control rely on digital communication technologies. The paper reviews various approaches to using these strategies to achieve different control objectives. It also discusses the dynamics and stability of DC MGs, highlighting that tightly regulated point-of-load (POL) converters can reduce system stability margins by introducing negative impedance, which may cause oscillations with lightly damped power supply input filters. The stability of the system is defined by the relationship between source and load impedances, referred to as the minor loop gain. Several prominent specifications for the minor loop gain are reviewed. Active stabilization techniques are also presented. The paper concludes that distributed control can achieve information awareness comparable to centralized control, enabling objectives such as output current sharing, voltage restoration, and global efficiency enhancement. However, distributed control has limitations in analytical performance analysis, especially in non-ideal environments. The paper also discusses the dynamics of regulated power supplies, emphasizing the role of line filters and the impact of POL converters on system stability. The paper concludes that the stability of DC MGs is crucial for safe and reliable operation, and that impedance-based analysis and stabilization techniques are essential for ensuring system stability.
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