No abstract

No abstract

Microgrids relying on cooperative control are supported by communications, which are highly vulnerable to cyberattacks. A significant amount of research is already carried out on the detection and mitigation of cyber attacks to secure the operation of DC microgrids. Although cyber attacks are fully capable of causing cascaded converter outages leading to full/partial system blackouts, disturbing the system stability can also be a viable target by the adversaries, which has been overlooked so far. Hence, this paper focuses on addressing the instability caused by stealth cyber attacks, which can easily bypass the well-defined observability tests. In addition, this paper also introduces a novel adaptive stabilization method to eliminate the unstable modes due to cyber attacks, which has been designed considering a previously defined cyber attack detection metric as an input. To investigate its feasibility, a detailed model of a stable DC microgrid is firstly developed. Then, considering stealth cyber attack as a non-linear element, the describing function-based method is used to investigate system stability under attack conditions. Finally, theoretical analysis, simulation and experimental results under various scenarios are presented to verify the effectiveness of the proposed stabilization scheme.

In a conventional photovoltaic (PV) DC microgrid system, mismatches among the PV modules due to partial shading will cause power loss. The distributed maximum power point tracking (DMPPT) can effectively solve the mismatch problem and achieve high-efficiency power output. This study proposes a maximum power range estimation method based on the DMPPT technique, which can provide guidance for designing parameters. Moreover, in order to realise seamless switching between different operation modes and ensure the stability of the DC microgrid, this study proposes a modified energy management and control strategy based on the hierarchical method. Simulation and experiment results indicate that the proposed control strategy for the DC microgrid based on the DMPPT technique can switch flexibly among different operation modes of the system, with a variation of environmental conditions and battery states, ensuring the stable bus voltage as well as safe operation.

Bipolarity in dc microgrids is desirable as it enhances the system's reliability and efficiency. However, the stability assessment for bipolar dc microgrid is challenging due to the integration of three-wire dc distribution line and numerous connected power converters, which is different from the stability analysis of conventional unipolar dc microgrid. In this paper, the basic form is arranged by generalized voltage source or current source, and the simplified form is derived by looking into different bus ports of a bipolar system in detail. Then, an impedance sum criteria-based stability conditions of different bus ports in the bipolar dc microgrid are proposed. To explore the mutual influence of the stability among different bus ports as well as investigate the stability issues caused by unbalanced loads connected to the symmetrical bus port, three cases are studied: 1) ±Vdc bus ports are connected with balanced and unbalanced loads; 2) -Vdc bus port introduces the photovoltaic unit and the energy storage unit; 3) The 2Vdc bus port introduces the photovoltaic unit and the energy storage unit. Finally, a ±24 V bipolar dc microgrid platform is set up to conduct experiments, verifying the accuracy and effectiveness of the stability evaluation method.

No abstract

No abstract

No abstract