In this paper, a seamless power management scheme is proposed for a decentralized DC microgrid (DCMG) to maintain voltage stabilization in the presence of voltage sensor faults. First, a voltage observer is constructed in each power agent to monitor the voltage sensor abnormality under various uncertain conditions. During the normal operations, the power balance as well as the voltage regulation of the DCMG is achieved by using the voltage droop control method which consists of the secondary controller and primary controller. While the secondary controller is utilized to maintain the DC-link voltage (DCV) at the nominal value, the power balance is achieved by the droop control method in the primary controller. In both controllers, the estimated DCV value is employed as the only feedback signal from the DC-link to the power agent. To maintain a seamless power management even under DCV sensor faults, a fault identification algorithm is first presented to detect voltage sensor failure. After the power agent recognizes its DCV sensor fault, its operation mode is switched from the voltage control to the current control mode, in which the operating point in the droop curves is perturbed by changing the current magnitude in the power agent with the faulty DCV sensor. The perturbation of operating point in the droop curves makes the other power agents with normal DCV sensor take a control of DCV instead of the power agent with the faulty DCV sensor to guarantee voltage stabilization and prevent the system collapse. Furthermore, the proposed scheme adjusts appropriately the droop curve of the utility grid agent in the primary controller under high electricity price condition to minimize electricity costs. Simulation and experimental results under various conditions verify the effectiveness and reliability of the proposed seamless power management strategy.

This paper presents a novel approach to manage distributed DC microgrids (DCMG) by integrating a time-of-use (ToU) electricity pricing scheme and an internal price rate calculation mechanism. The proposed power-management system is designed to effectively handle uncertainties such as utility grid (UG) availability, fluctuating electricity prices, battery state of charge (SOC) levels, and frequent plug-ins and plug-outs of electric vehicles (EVs). Uncertainties in DCMG systems often lead to inefficiencies, power imbalances, and inexact voltage regulation issues within DCMGs. In addition, to maintain the power balance and constant voltage regulation under various operational states, the proposed scheme also incorporates secondary control into the DCMG power-management system. Unlike the existing approaches that often fail to adapt dynamically to changing conditions, the proposed method is the first approach to consider the concept of internal price rate in designing the DCMG power management. To address this challenge, this approach proposes a more resilient power-management strategy to enhance the efficiency and adaptability of DCMG systems. Extensive simulations and experimental validations demonstrate the practicality and adaptability of the proposed control strategy under diverse test conditions, including operation transitions between grid-connected mode (GCM) and islanded mode (IM), low battery SOC condition, operation transition from the current control mode (CCM) to distributed secondary control mode (DSCM), and EV plug-in scenarios. The test results confirm that the proposed method enhances the reliability, efficiency, and economic viability of DCMG systems, making it a promising solution for future smart grid and renewable energy integrations.

A seamless distributed power management for the dc microgrid (DCMG) with bidirectional power flow is presented in this paper to achieve the overall system stabilization even under severe cyber attacks. First, a distributed secondary control (DSC) based on the V*-P droop curves is presented to ensure the power and voltage regulation for the DCMG system consisting of the electric vehicle (EV), wind turbine, battery, load, and utility grid agents under uncertain conditions. The proposed scheme automatically adjusts the utility grid droop curve to minimize electricity expenditure under electricity price change. To eliminate the negative effect of severe cyber attacks such as false data injection (FDI) and denial-of-service (DoS) in the distributed DCMG system, a resilient DSC based on the compensation term is utilized in the proposed scheme. In addition, by modifying the DSC structure of each power agent, the proposed scheme reduces the overshoot of the dc bus voltage even in the presence of the electricity price change, agent power variation, sudden utility grid disconnection, or critical state-of-charge (SOC) levels. Furthermore, the proposed distributed DCMG system utilizes only the unidirectional digital communication links (DCLs) to cut down the system cost and communication burden, which greatly simplifies communication structure. The efficiency and feasibility of the proposed distributed power management are validated by simulation and experimental results under various conditions.

Continuous power management for a decentralized DC microgrid (DCMG) is proposed in this study to achieve power balance and voltage regulation even under system uncertainty and voltage sensor failure. The DCMG system achieves continuous power management through only the primary controller to reduce the computational burden of each power agent. To enhance the reliability and resilience of the DCMG system under DC bus voltage (DCV) sensor failure, a DCV sensor fault detection algorithm is suggested. In this algorithm, DCV sensor failure is detected by comparing the measured DCV with the estimated DCV. If power agents identify the failure of the DCV sensor, it changes the operation properly according to the proposed control mode decision algorithm to guarantee the stability of the DCMG system. When uncertain conditions like sudden grid disconnection, DCV sensor failure, electricity price change, power variation in distributed generations, and critical battery status occur, the DCMG system is changed to transitional operation modes. These transitional operation modes are employed to transmit the power agent information to other agents without digital communication links (DCLs) and to accomplish power sharing even under such uncertain conditions. In the transitional operation modes of the DCMG system, the DCV levels are temporarily shifted to an appropriate level, enabling each power agent to detect the uncertainty conditions, and subsequently to determine its operation modes based on the DCV levels. The reliability and effectiveness of the proposed control strategy are confirmed via various simulation and experimental tests under different operating conditions.

To maintain voltage stabilization under transmission time delays, this paper proposes a seamless power management scheme for a distributed DC microgrid (DCMG) with minimum digital communication links (DCLs). First, a DCL topology with minimum communication data is presented for the construction of distributed DCMG system not only to mitigate the communication burden but also to enhance the system’s flexibility and reliability. In addition, based on information gathered from nearby agents and local measurements, the operating modes of local agents in a DCMG system are determined properly to ensure a proper power balance under various conditions. During normal operation, the proposed scheme works as a distributed control scheme either in the grid-connected or islanded mode to take advantage of the distributed control method. To maintain seamless power management even under transmission time delays such as grid fault detection delays and grid recovery detection delays, the operating modes of each agent in a DCMG system are switched to a decentralized scheme based on the droop control method. When the utility grid information is properly identified by all power agents after a transmission time delay, the DCMG system returns to the distributed control scheme based on DC-link voltage (DCV) control to guarantee voltage stabilization. Furthermore, the scalability issue of a distributed DCMG system is also considered in this paper when an additional energy storage system (AESS) agent is involved in the DCMG system. For this purpose, a DCL topology with minimum communication data is designed for the AESS, which enables power units to participate in or to leave the distributed DCMG system easily. Simulation and experimental results under various conditions demonstrate the effectiveness and reliability of the proposed seamless power management strategy.

To enhance the reliability and flexibility of DC microgrids (DCMGs), this paper presents a decentralized power flow control strategy (PFCS) by using the transition operation modes. The transition operation modes are introduced as an effective communication method among power units, eliminating the use of additional digital communication links (DCLs) for the purpose of ensuring the power balance as well as the voltage regulation even under uncertain conditions. During the transition operation modes, the power unit which transmits the information shifts the DC-link voltage level, and the power unit which receives the information continuously monitors the DC-link voltage with predetermined time. When uncertain conditions occur in a particular power unit, this power unit triggers the transition operation modes to send this information to all power units in the DCMG system. The proposed PFCS can maintain the DC-link voltage at the nominal value for steady-state conditions both in the grid-connected mode and islanded mode. Moreover, the proposed PFCS significantly enhances the overall reliability of the decentralized DCMG system by effectively addressing several uncertainties stemmed from electricity price fluctuations, grid availability, battery state-of-charge (SOC) levels, and wind power variations. The scalability of the DCMG system is also demonstrated by incorporating an electric vehicle (EV) unit as an additional energy storage system (ESS). The EV unit seamlessly cooperates with the existing battery unit, functioning as additional ESS to regulate the DC-link voltage when the battery SOC level is low. Simulation and experimentation results under various conditions demonstrate the effectiveness of the proposed PFCS.