基于小信号模型的微网控制参数选择与稳定性分析

Control Parameter Selection and Stability Analysis of Microgrid Based on Small-signal Model

小信号稳定性是微网运行的关键问题之一,特别是孤岛运行时,控制器结构较为复杂,且缺少大电网的电压频率支撑。为此,以未来可再生电能传输和管理(future renewableelectric energy delivery and management,FREEDM)网络为对象,推导固态变压器(solid state transformer,SST)、网络线路及负荷模型的状态空间方程,建立完整的微网小信号模型,分析孤岛运行时的稳定性,并根据其状态矩阵特征值及灵敏度,确定影响系统稳定的关键参数,设计配置多SST的环形微网,仿真验证选取的控制器参数的正确性。结果表明,系统对负荷突变和随机波动都具有很强的适应性,且具有良好的环流抑制效果。所建小信号模型可用于微网稳定性分析及控制器参数的优化设计。

Small-signal stability is one of the key issues in microgrid operation, especially for islanding modes, since the controller is complex and the microgrid can＇t obtain voltage and frequency reference from the main grid. Therefore, taking future renewable electric energy delivery and management （FREEDM） network as research object, this paper derived the full state-space equations of solid state transformer （SST）, distribution network and loads, and established a complete small-signal model of microgrid to analyze the system stability during islanded operation. The key parameters affecting system stability were determined according to eigenvalues and sensitivity analysis. A loop type microgrid with multi-SST was designed and simulation tests were performed to verify the correctness of the selected controller parameters. The simulation results show that the system has strong adaptability to load mutation and random fluctuation and has good performance on restraining loop current. The small-signal model can be applied to microgrid stability analysis and optimization of controller parameters.