Efficient Operations of Micro-Grids with Meshed Topology and Under Uncertainty through Exact Satisfaction of AC-PF, Droop Control and Tap-Changer Constraints
Efficient Operations of Micro-Grids with Meshed Topology and Under Uncertainty through Exact Satisfaction of AC-PF, Droop Control and Tap-Changer Constraints
复制标题
DOI：
10.3390/en15103662
复制
发表时间：
2022-05
期刊：
影响因子：
3.2
通讯作者：
Mikhail A. Bragin;B. Yan;Akash Kumar;N. Yu;P. Zhang
中科院分区：
文献类型：
--
作者：
Mikhail A. Bragin;B. Yan;Akash Kumar;N. Yu;P. Zhang
微电网的运行提供了当地的可靠性;在公用事业方面发生故障或低电压/低频率事件时，微电网可以与主电网断开连接，自主运行，同时为当地客户提供持续的电力供应。然而，随着可再生能源发电的日益普及，由于相关的电压波动，微电网的操作变得越来越复杂。结果，频繁地调节Transformer抽头，从而导致昂贵的抽头变换变压器的快速劣化。在孤岛模式中，困难还来自于从主电网断开时的电压和频率的下降。为了对上述内容进行适当建模，需要非线性交流潮流约束。在计算上，分接开关操作的离散性和可再生能源引起的随机性在复杂的AC-OPF问题上增加了两层难度。为了解决上述计算困难，最近发展的“l1-proximal”代理拉格朗日松弛的主要原则进行了扩展。基于九节点系统的测试结果表明，该方法能够有效地获得微电网运行的精确可行解，从而避免了现有方法固有的近似;特别是，该方法快速收敛到可行解。它也表明，通过优化，抽头变化的数量大大减少，该方法是能够有效地处理网络与网状拓扑结构。
Micro-grids’ operations offer local reliability; in the event of faults or low voltage/frequency events on the utility side, micro-grids can disconnect from the main grid and operate autonomously while providing a continued supply of power to local customers. With the ever-increasing penetration of renewable generation, however, operations of micro-grids become increasingly complicated because of the associated fluctuations of voltages. As a result, transformer taps are adjusted frequently, thereby leading to fast degradation of expensive tap-changer transformers. In the islanding mode, the difficulties also come from the drop in voltage and frequency upon disconnecting from the main grid. To appropriately model the above, non-linear AC power flow constraints are necessary. Computationally, the discrete nature of tap-changer operations and the stochasticity caused by renewables add two layers of difficulty on top of a complicated AC-OPF problem. To resolve the above computational difficulties, the main principles of the recently developed “l1-proximal” Surrogate Lagrangian Relaxation are extended. Testing results based on the nine-bus system demonstrate the efficiency of the method to obtain the exact feasible solutions for micro-grid operations, thereby avoiding approximations inherent to existing methods; in particular, fast convergence of the method to feasible solutions is demonstrated. It is also demonstrated that through the optimization, the number of tap changes is drastically reduced, and the method is capable of efficiently handling networks with meshed topologies.