基于下垂控制结构微网小扰动稳定性分析

Small signal stability analysis of microgrid droop controlled power allocation loop

介绍了下垂控制原理和机组输出功率计算方法,针对取较大下垂系数难于保证微网功率分配外环稳定性问题,在有功下垂控制环节中增设前馈环节来改善微网小扰动稳定性。建立了微网小信号模型,系统分析了下垂系数、线路阻抗、滤波系数及前馈环节等对微网小扰动稳定性影响,验证了前馈环节能明显改善微网小扰动稳定性,从而功率分配外环可取较大下垂系数,有利于降低配电网频率和电压波动对机组输出功率的影响以及提高无功负荷分配精度。最后建立微网仿真实验,通过合理选取前馈系数来配置微网小信号模型主导共轭特征根。

First, the principle of the droop control and the power calculation method is introduced. In order to overcome the disadvantage of big droop coefficients on the stability of the power allocation loop, here a feed forward path on the real power droop block is added to improve the stability. Then the small signal model of the microgrid is established, the impacts of droop coefficients, line resistance and reactance, filter and feed forward coefficients＇ on the stability is systematically analyzed, which confirms that the feed forward path can improve the stability significantly, so the power allocation loop can adopt big droop coefficients to lower its sensitivity on the fluctuation of the frequency and voltage of the distribution network, as well as improve the reactive Ioad distribution accuracy. At last, the time domain simulation is conducted to confirm the necessity of adopting appropriate feed forward coefficients to configurate the dominant conjugate eigenvalue of small signal model.