下垂控制交直流微电网的潮流算法研究

Research on Power Flow Algorithm for Droop-controlled AC/DC Microgrid

  • 摘要: 随着分布式能源的普及,交直流混合微电网因其能高效接纳各类电源与负载而备受关注。其中,孤岛运行的下垂控制微电网无需依赖主网、自主性强,是未来的重要发展方向。然而,此类系统的潮流分析与传统电网有本质区别:系统呈孤岛运行缺乏平衡节点、分布式电源采用下垂控制、交流子系统频率与直流子系统电压通过互联变流器紧密耦合,使得传统以单一平衡节点为基础的潮流算法不再适用。算法通过考虑互联变流器的功率传输,将交、直流网络的耦合关系量化为连接处的交互功率。通过迭代更新该交互功率,将复杂的整体问题转化为两个可独立求解的子问题。针对每一个子问题,在考虑下垂特性的基础上,对传统前推回代法进行改进求解。最后通过仿真算例对算法的精确性和收敛快速性加以验证。算法为系统的规划、运行与控制提供了有效的分析工具。

     

    Abstract: With the proliferation of distributed energy resources, hybrid AC/DC microgrids have garnered significant attention due to their ability to efficiently integrate various power sources and loads. Among them, islanded microgrids employing droop control, which operate independently without reliance on the main grid, offer strong autonomy and represent a key future development direction. However, the power flow analysis for such systems differs fundamentally from that of traditional power grids: the system operates in an islanded mode without a slack bus, distributed generators utilize droop control, and the AC subsystem frequency is tightly coupled with the DC subsystem voltage through interlinking converters. These characteristics render traditional power flow algorithms based on a single slack bus inapplicable. The proposed algorithm addresses this by modeling the power transfer of the interlinking converters, quantifying the coupling relationship between the AC and DC networks as the interactive power at their point of connection. By iteratively updating this interactive power, the complex overall problem is decomposed into two independently solvable subproblems. For each subproblem, an improved forward-backward sweep method, which does not require derivative calculations, is applied to solve the power flow, taking into account the distinctive droop characteristics of each subgrid. Finally, simulation case studies verify the algorithm's accuracy and rapid convergence. This algorithm provides an effective analytical tool for the planning, operation, and control of such systems.

     

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