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.
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