逆变型分布式电源微网小信号稳定性动态建模分析

Small-signal Dynamic Modeling and Analysis of a Microgrid Composed of Inverter-interfaced Distributed Generations

现有微网小信号稳定性分析中,通常忽略网络和负荷的实际动态特性且对分布式电源逆变器采用理想建模,导致分析结果产生一定误差。为更准确分析微网和大容量逆变器的动态性能,建立了逆变型分布式电源微网的小信号动态模型,主要包括2个子模型:网络及负荷小信号动态子模型和电压、电流双闭环控制逆变器的小信号动态子模型。利用该模型计算了有功负荷增加20%情况下的阶跃响应,并运用PSCAD/EMTDC软件对相同运行状态进行了仿真,两者对比验证了所提出模型的正确性。应用该模型时,通过计算其特征值便可直观分析微网的小信号稳定性,在进一步对特征值进行敏感度分析的基础上,找出影响主低频特征值的状态变量。该模型的建立可为控制器参数的优化设计提供依据,且有助于提高微网小信号的稳定性。

The ideal inverter model and stale-less impedance model of network and loads are currently used to analyze the small- signal stability of a microgrid, which will cause important dynamics to be omitted. To capture the dynamics of a microgrid and large power inverters more accurately, a complete small-signal model of a microgrid composed of inverter-interfaced distributed generations is developed. This integrated model consists of two sub-models： one is the small-signal sub-model of network and loads considering dynamics and the other is the small-signal sub model of inverters including voltage and current controller dynamics. Using the model constructed, the step response results with the active load increased by 20% are obtained, which are verified by the results obtained from simulation of the same situation in PSCAD/EMTDC. The eigenvalues of state matrix of the small signal model for a microgrid can be used to directly investigate the small-signal stability. A sensitivity analysis is further performed to help identify the origin of the dominant low frequency eigenvalues. The development of the model can optimize the control parameters and improve the small signal stability of a microgrid.