考虑非线性阻尼效应的孤岛微电网暂态稳定性分析及提升策略研究

Transient Stability Analysis and Improved Control Strategy for Islanded Microgrid Considering Nonlinear Damping Effect

随着可再生能源发电及并网技术的快速发展,以电力电子变流设备为主导的微电网受到了越来越多的关注。由于电力电子变流器的低惯量和强非线性特征,孤岛微电网在大扰动下易发生暂态失稳。考虑微电网中构网逆变器与跟网逆变器的交互作用,提出1种基于等面积法则的暂态稳定性判据和暂态稳定提升控制策略。首先,建立了孤岛微电网的简化二阶动态模型,包含依赖于功角的非线性阻尼项。然后,从能量角度分析了非线性阻尼对加减速面积的影响规律。考虑非线性阻尼的分布特性,推导出正阻尼区域内的暂态稳定性判据。根据稳定边界条件,提出1种基于电压前馈的暂态稳定性提升控制策略。最后,利用MATLAB/Simulink仿真对所提稳定性判据和改进控制策略的有效性进行了验证。结果表明,所提微电网暂态稳定性判据和改进控制策略可为电力电子变流器的参数优化设计和提高微电网稳定运行能力提供理论依据。

With the rapid development of power generation by renewable energy and the grid-connection technology,the microgrid dominated by power electronic converters has attracted more and more attention in recent years.Owing to the low inertia and high nonlinearity of power electronic converters,an islanded microgrid under large disturbances is more likely to lose its transient stability.Considering the interactions between grid-forming and grid-following converters in the microgrid,a transient stability criterion based on the equal area criterion(EAC)and an improved control strategy for transient stability are proposed.First,the simplified second-order dynamic model of the islanded microgrid is established,which contains a nonlinear damping term relying on the power angle.Then,the impact of the nonlinear damping term on the acceleration and deceleration areas is revealed from the energy perspective.Considering the distribution characteristics of nonlinear damping,a transient stability criterion is formulated for the positive damping region.In addition,according to the stable boundary conditions,an improved control strategy for transient stability based on voltage feedforward is also put forward.Finally,simulations are carried out with MATLAB/Simulink to verify the effectiveness of the proposed stability criteria and the improved control strategy.The results show that the microgrid transient stability criterion and the improved control strategy proposed can provide a theoretical basis for the parameter optimization design of power electronic converters and the improvement of the stable operation capability of microgrid.