直流微电网建模与稳定性分析

Modeling of DC micro-grid and stability analysis

针对直流微电网的稳定性问题,采用状态空间法建立了直流微电网中多种变流装置及其控制系统的平均模型,并在此基础上对直流微电网进行了小扰动稳定性分析,得出了随着变流器控制参数变化的系统特征值轨迹。分析表明,当变流器的控制系数增大到一定数值时,将会出现实部为正的系统特征值,即系统不稳定。为了验证这一分析方法的可行性,又对所研究的直流微电网进行了时域仿真,得出负荷突增时不同控制系数下的时域电压曲线。仿真结果一方面验证了稳定性分析的结果,另一方面也表明,当控制系数在稳定范围内时,系数越大,则电压控制的效果也越好。由此可见,合理选择变流器的控制参数能够很好地保证直流微电网的电压稳定性。

The average models of various converters and their control systems are establisned Dy state-space approach ,based on which the small disturbance stability of DC micro-grid is analyzed to obtain the loci of system eigenvalues versus converter control parameters. It shows that,when control parameter increases to a certain value,the real part of eigenvalue becomes positive ,i.e. the system becomes instable. The time-domain simulation is carried out to obtain the voltage curves under different control parameters,which validates the practicability of proposed analysis method. It also shows that,within the stable range,the larger the control parameters are,the better the voltage control performance is. It is concluded that,the proper setting of converter control parameters ensures the voltage stability of DC micro-grid.