孤岛运行的交直流混合微电网小信号稳定性分析

Small Signal Stability Analysis of AC/DC Hybrid Microgrid Under Isolated Island Operation

与纯交流微电网相比,交直流混合微电网具有诸多优势,是目前的研究热点。当交直流混合微电网与大电网断开,孤岛运行时,由于各个分布式电源(distribution generation,DG)均是电力电子接口,系统惯性较小,而且交流侧与直流侧通过主变流器相互耦合,一侧的不稳定必然会影响到另一侧,因此,其小信号稳定性问题变得更为复杂。该文建立了包含DG、储能、负荷以及主变流器的交直流混合微电网模型,对其进行了特征值分析并找出了系统的主要振荡模式以及其阻尼比、所对应的状态变量等信息。通过根轨迹分析法,改变特定元件的参数,提高了低阻尼振荡模式的阻尼比,有效改善了系统的稳定性,并通过时域仿真对小信号分析结果进行了验证。

Compared with pure AC microgrid,AC /DC hybrid microgrid has many advantages,which has become a hot topic. When AC /DC hybrid micro-grid is disconnected with power grid and under isolated island operation,because that each distribution generation（ DG） is power electronic interface,the system inertia is small; and the AC side and the DC side are coupled to each other through the main converter,the unstable side is bound to affect the other side,so the small signal stability problem becomes more complex. This paper establishes the model for AC /DC hybrid microgrid which including DG,energy storage,load and main converter,then finds out the system＇s main oscillation mode and its damping ratio,corresponding state variables through eigenvalue analysis. The proposed method can change the parameters of a particular element to improve the damping ratio in low damping oscillation mode by root locus analysis. What＇s more,it effectively improves the stability of the system,and the small-signal analysis results are verified through time-domain simulation.