逆变型分布式电源微网并网小信号稳定性分析

Small-signal Stability Analysis of Grid-connected Microgrid with Inverter-interfaced Distributed Resources

为研究逆变型分布式电源微网并网运行的小信号稳定性,建立了完整的并网运行微网小信号动态模型,主要包括2个子模型:网络及负荷小信号动态子模型和功率(或电压)、电流双环控制逆变器小信号动态子模型。应用所建立的模型,首先分析了主网与微网之间联络阻抗对并网运行微网小信号稳定性的影响,得出联络阻抗过大不利于微网保持小信号稳定的结论;其次比较了逆变器采用PQ和PV控制时主特征根实部和虚部的特点,得出PV控制能有效抑制电压振荡,其暂态性能优于PQ控制的结论。最后在分布式电源指定有功输出增加15%的情况下,通过比较PQ和PV控制时的系统响应,验证了上述结论。

To study the small-signal stability of grid-connected microgrid with inverter-interfaced distributed resources,a complete small-signal dynamic model of the grid-connected microgrid is developed.The model consists of two sub-models： a dynamic sub-model of network and loads,and a dynamic sub-model of inverter adopting power（or voltage） and current double-loop control.Firstly,how the equivalent impedance between the penetrated distribution network and the microgrid impacts on the small-signal stability of the microgrid is studied.It is concluded that large equivalent impedance is harmful to the small-signal stability.Secondly,the real and imaginary parts of dominant eigenvalue are compared when the inverter adopts PQ and PV control strategies respectively.It is found that PV control is a desirable approach than PQ control because PV control can eliminate the potential voltage oscillations.The above conclusions are verified by simulation of PQ and PV control responses to a 15% step change of reference output power of a distributed resource.