频率突变对孤岛微电网暂态建模及稳定性的影响分析

Impact analysis of frequency mutation on transient modeling and stability of islanded microgrid system

随着新能源渗透率的提高,电力系统逐步呈现出电力电子化特性。以并网逆变器为主导的孤岛微电网系统近年来受到越来越多的关注。一种类似于同步发电机的变流器摆动方程被建立,并广泛应用于孤岛微电网的暂态稳定性分析,但其忽略了由公共耦合点电压突变引起的锁相环频率突变。首先,推导了传统的孤岛微电网二阶数学模型,通过理论分析与数值计算发现现有模型存在一定的误差和时延,进一步发现误差是扰动瞬间产生的频率突变所致。通过计算频率突变量对既有的传统二阶数学模型进行修正,提高了暂态扰动下的数学模型精度。同时,分析了不同扰动对系统同步稳定性的影响规律。最后利用Matlab/Simulink仿真和RT-Lab硬件在环实验对所提出的理论分析结果进行了验证。

With the increase of new energy penetration rate, the power system gradually presents the characteristics of power electronization. The islanded microgrid system dominated by grid-connected inverters has attracted more and more attention in recent years. The oscillation equation similar to the synchronous generator has been established and widely used in transient stability analysis of islanded microgrids, but the frequency mutation of phase locked loop caused by common coupling point voltage mutation is ignored. Firstly,the traditional second-order mathematical model of islanded microgrid is deduced. Through theoretical analysis and numerical calculation results, it is found that there are certain errors and time delays in the existing model. It is further found that the error is caused by the frequency mutation generated at the moment of disturbance. By calculating the frequency mutation, the classical second-order mathematical model is corrected, and the accuracy of the mathematical model under transient disturbance is improved. The influence of different disturbances on the synchronization stability of the system is also analyzed. Theoretical analysis is verified by Matlab/Simulink simulation and RT-Lab hardware-in-the-loop experiment.