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In this paper, an optimal consensus-based event-triggered control strategy is proposed to coordinate multiple distributed energy resources (DERs) in a dc microgrid. In the proposed control strategy, the average bus voltage restoration and the proportional current sharing are integrated by transforming the coordinated control problem into an optimization problem. The proposed solution enhances the resilience of the controller strategy in extreme events with uncertain initial states. Accordingly, the proposed control strategy provides a sampled-data-based event-triggered mechanism considering the limited availability of communication resources, which reduces communication burdens and avoids Zeno behaviors. The sufficient conditions are demonstrated using the Lyapunov–Krasovskii functional method for maintaining the stability of the proposed control strategy. Several case studies are presented using the PSCAD/EMTDC platform and the results are discussed to validate the effectiveness of the proposed control strategy for enhancing the dc microgrid resilience. [ABSTRACT FROM AUTHOR]

Hybrid energy storage system (HESS) consisting of battery and supercapacitor (SC) is an effective approach to alleviate voltage stability problems brought by the fluctuation of renewable resources in a dc microgrid. This paper proposes a novel distributed control scheme for multiple HESSs based on a leaderless consensus protocol to realize the power splitting between batteries and SCs and thus regulate the dc bus voltage. Without assigning leaders among the batteries and SCs, each SC or battery has equal priority in participating in voltage or state of charge (SOC) regulation using only neighboring information exchange instead of global communication. This distributed approach makes the system robust against any physical failure or communication fault only if the remaining communication network is connected. Consensus for the state variable associated with the battery SOC, the SC terminal voltage, and the dc average bus voltage are all achieved in this scheme, and thus the voltage quality and the energy storage lifetime can be improved. In addition, the small-signal stability of a four-HESS system is investigated, and the impact of the control parameters on the system is analyzed. Simulations and experimental studies are conducted to demonstrate the effectiveness of the proposed control scheme in an islanded dc microgrid. [ABSTRACT FROM AUTHOR]

Recently, dc electric springs (dc-ESs) have been proposed to realize voltage regulation and power quality improvement in dc microgrids. This paper establishes a distributed cooperative control framework for multiple dc-ESs in a dc microgrid and presents the small-signal stability analysis of the system. The primary level implements a droop control to coordinate the operations of multiple dc-ESs. The secondary control is based on a consensus algorithm to regulate the dc-bus voltage reference, incorporating the state-of-charge (SOC) balance among dc-ESs. With the design, the cooperative control can achieve average dc-bus voltage consensus and maintain SOC balance among different dc-ESs using only neighbor-to-neighbor information. Furthermore, a small-signal model of a four dc-ESs system with the primary and secondary controllers is developed. The eigenvalue analysis is presented to show the effect of the communication weight on system stability. Finally, the effectiveness of the proposed control scheme and the small-signal model is verified in an islanded dc microgrid under different scenarios through simulation and experimental studies. [ABSTRACT FROM PUBLISHER]

Recent events have shown that cyber attacks are becoming real threats to the power system reliability and resiliency, and there is no exception to the DC microgrids which would become popular in the future. Currently, most secondary controls in DC microgrids heavily rely on communications, making them specifically vulnerable to cyber attacks. This paper presents a resilient distributed control based on the average consensus algorithm and the proportional-integral (PI) consensus algorithm to enhance the system resilience against denial of service attacks and improve the microgrid stability, particularly in the presence of constant power loads. The proposed control casts the average voltage restoration problem into an optimization problem, and because of this, the voltage control is immune to the communication damage caused by malicious denial of service attacks. Moreover, the small-signal stability model of the DC microgrid with distributed energy storages and constant power loads is established, and the impacts of varying constant power loads, controller parameters and communication topology on the system stability are analyzed. Simulations are conducted to verify the effectiveness of the proposed method. • Global voltage and current regulations are realized by distributed mechanisms. • Distributed controllers can keep the DC microgrids stable during cyber-attacks. • Proportional-integral consensus based controllers can recover from Denial of Service attacks. • Distributed controllers contribute to improving stability in the presence of constant power loads. [ABSTRACT FROM AUTHOR]

Highlights • A virtual capacitor droop control (CDC) using fuzzy logic algorithm in multiple HESSs can adaptively adjust the droop coefficient, so as to eliminate the impact of the line impedance on the power splitting and improve the power sharing accuracy. This study has not been reported in previous work. • Both the small-signal model and eigenvalue analysis are presented to study the stability of the HESS system using CDC, investigate the impact of the droop coefficient variation on the system dynamics and determine an optimal range of the modified droop coefficient. This work has not been involved in the previous studies. Abstract In a DC microgrid, virtual capacitor droop control (CDC) can achieve power allocation according to different frequency characteristics of a hybrid energy storage system (HESS). However, the control performance may be easily affected by the line impedance. In this paper, an adaptive droop controller based on a fuzzy logic algorithm is proposed. By detecting the unbalanced power and the voltage deviation, the droop coefficient can be adaptively adjusted to mitigate the influence of the line impedance and achieve desirable power splitting in the HESS. Furthermore, the small-signal model of the HESS is established and the impact of the droop coefficient variation on the stability of the DC microgrid is exploited. The simulation results in PSCAD/EMTDC verify the effectiveness of the proposed adaptive droop controller. It has been proved that desirable power splitting can be obtained among multiple HESSs under different scenarios. [ABSTRACT FROM AUTHOR]