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With the increment of grid complexity and voltage level, the effect of geomagnetic induced current (GIC) on the grid is also increasing. There is no complete system to assess the impact of GIC on the reliability of the grid at present. This paper discusses the relationship between geomagnetic data and transformer failure rate. Referring to the existing mathematical model between GIC indices and failure rate, Monte–Carlo method is used to calculate the reliability of a given system under the influence of geomagnetic storm. The case study shows the validity of the assessment and this paper contributes to the establishment of a complete reliability evaluation system. [ABSTRACT FROM AUTHOR]

Hybrid ac/dc distribution has attracted much attention recently. This study presents a medium-voltage (MV) hybrid ac/dc distribution consisting of various distributed generations connecting to the ac and dc loads. Coordination control in hybrid ac/dc distribution is a challenging issue to achieve stability especially when there is a load rejection or loss of the generation. A new decentralised control is proposed to coordinate the hybrid ac/dc distribution even when the inter-station telecommunication is not available. A new control is employed at interlinking converter (ILC) to maintain the power balance between ac and dc subgrids, and to ensure that the power quality is maintained in normal operating condition as well as in an extreme abnormal condition such as island mode. Further, a new control strategy is developed in battery storage system (BES) as a backup device to minimise the power fluctuation in the event of the shedding of the loads or generations. Another advantage of the combination of ILC and BES controllers is to provide a multiple slack terminals in both ac and dc grids, which will enhance the stability in the system. Simulation results have shown that the stability performance can be achieved in various operating scenarios. [ABSTRACT FROM AUTHOR]