With the continuous increase of distributed energy resources (DERs) and renewable energy sources, the power system is facing different operational challenges i.e. reliability and resilience of the electrical grid. To solve these problems the concept of a microgrid, particularly hybrid microgrid, has gained significant attention worldwide. The Hybrid microgrid can accommodate both DC and AC grids and the existence of both grids leads to the idea where both grids are tied via inter-linking converter (ILC) that can facilitate the power transfer among both grids. In this paper, an improved droop control scheme for the control of hybrid microgrid is presented along with a frequency and active power-based droop of the ILC. Moreover, to determine the droop coefficient of the ILC, scaling factors are applied. Hence, this allows the ILC to facilitate the transfer of power between the overloaded and under-loaded grid. Two main scenarios involving single and multiple hybrid microgrids are considered in this study. The results show that the frequency variation in the AC grid occur, when any change in load occurs in the DC grid and vice versa. In this way, the droop-based ILC balances the power between the under-loaded and overloaded grids.

中文翻译：

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交直流混合微电网中基于下垂控制的频率和电压方法

随着分布式能源（DER）和可再生能源的不断增加，电力系统面临着不同的运行挑战，即电网的可靠性和弹性。为了解决这些问题，微电网的概念，特别是混合微电网，在世界范围内引起了极大的关注。混合微电网可以同时容纳直流和交流电网，并且两个电网的存在导致两个电网通过互连转换器 (ILC) 连接的想法，这可以促进两个电网之间的电力传输。在本文中，提出了一种用于控制混合微电网的改进下垂控制方案以及基于频率和有功功率的 ILC 下垂。此外，为了确定 ILC 的下垂系数，应用了缩放因子。因此，这使得 ILC 能够促进过载和欠载电网之间的电力传输。本研究考虑了涉及单个和多个混合微电网的两个主要场景。结果表明，当直流电网中发生任何负载变化时，交流电网中的频率会发生变化，反之亦然。通过这种方式，基于下垂的 ILC 平衡了欠载和过载电网之间的功率。