EPCs (Electronic Power Converters) are the key elements of the smart dc microgrid architectures. In order to enhance the controllability of the system, most of the elements are envisioned to be connected to the different buses through EPCs. Therefore, power flow, stability, and dynamic response in the microgrid are function of the behavior of the EPCs and their control loops.Besides, dc microgrids constitute a new paradigm in power distribution systems due to the high variability of their operating conditions, owing to the intermittent behavior of the renewable sources and customer energy consumption. Furthermore, in order to deal with this variability, the power converters can modify their operation mode, adding complexity to the dynamic and stability analysis of the system. This paper gives an overview of the various analytical and blackbox modeling strategies applied to smart dc micro/nanogrids. Different linear and nonlinear modeling techniques are reviewed describing their capabilities, but also their limitations. Finally, differences among blackbox models will be highlighted by means of illustrative examples.

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The smart grid concept is increasingly becoming popular within the academia and industry. The integration of electronic power converters as an enabler for the massive deployment of distributed renewable energy sources, along with the inclusion of control, monitoring and automation systems in the grid, has drawn the attention of many researchers. Furthermore, a transition towards dc distribution is currently under investigation due to its more suitable interface with most of the modern loads and sources, which offers benefits in terms of size, cost and reliability of the whole system.This paper proposes a black-box polytopic modeling approach as a tool for the system-level design of dc based nanogrids. This strategy allows both small and large-signal analysis of power distribution systems even when commercial off-the-shelf converters have to be integrated. In addition, the main characteristics of the dc bus signaling control, i.e. droop control, changes in power converter control mode and disconnection of loads, have been incorporated in the modeling structure.

Abstract-The Dowell expression is the most commonly used method for the analytic calculation of the equivalent resistance in windings of magnetic components. Although this method represents a fast and useful tool to calculate the equivalent resistance of windings, it cannot be applied to components that do not fit with classical ID assumption, which is the case of gapped magnetic components. These structures can be accurately analyzed using finite-element analysis (FEA) with the time cost that this represents.Modifying the Dowell s equation, and taking advantage of the orthogonality between skin and proximity effects, a simple solution that allows its application in gapped magnetic components is proposed in this work, which results shows a very good accuracy compared with experimental measurements.