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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]

The distributed controller consisting of a voltage controller and a power controller is commonly employed on the secondary control layer in the DC microgrid. In this paper, a novel optimal control based on the PI consensus algorithm is proposed for multiple battery energy storages (BESs) in an islanded DC microgrid. Compared with the conventional distributed voltage controller, the proposed scheme improves the system robustness to time delays. The steady-state analysis is conducted to verify that the proposed scheme can take effect in case of time delays. The impact of the secondary controller on the dynamics of the system under time delays is investigated by the eigenvalue analysis. Simulation results confirm that favorable power sharing and DC voltage regulation as well as robustness to time delays achieved by optimal control in an islanded microgrid with multiple BESs and constant power load (CPL). [ABSTRACT FROM AUTHOR]

For a distributed DC microgrid, the conventional voltage control highly relies on the accuracy of the voltage observer, and the observer will produce an estimation error under time delays. To address the problem brought by the voltage observer, this paper transforms the voltage control into an optimization problem and integrates it into the power sharing control based on the PI consensus algorithm. With the proposed optimal control, the DC bus voltage control and proportional power sharing of the energy storages can be realized in one controller, so that the controller structure is dramatically simplified and the control accuracy will not be affected by the time delay. In addition, to further improve the system stability to resist delay, scattering transformation is introduced in the distributed optimal controller. By constructing Lyapunov function, it has been proved that the stability of the controller under the time delay can be guaranteed. Simulations are conducted to verify the effectiveness of the proposed control strategy and the transformation with and without time delay. [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]

For distributed heterogeneous energy storage systems (HESSs) in a dc microgrid, a virtual impedance droop (VID) control, composed of virtual resistance droop control and virtual capacitor droop control, can realize low- and high-frequency power sharing between a battery and supercapacitor (SC) automatically. However, it still suffers from voltage deviation. In this paper, a secondary voltage recovery (SVR) control is proposed for a battery and SC on the basis of VID control. The SVR control for batteries is designed to regulate the average bus voltage to the reference value, depending on the communication between neighboring batteries. Nevertheless, the SVR control for SCs is decentralized to facilitate fast recovery of the state of charge, in spite of the existence of leakage current. Detailed impedance characteristics analysis and small-signal stability analysis are performed to find that the proposed SVR control does not affect the power sharing dominated by the primary VID control and the system stability. Simulations for both a single HESS and multiple HESSs are conducted to verify the effectiveness of the proposed control strategy. [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]