大区电网弱互联对互联系统阻尼和动态稳定性的影响

全国电网互联后系统中将普遍出现低频振荡现象。该文从阻尼转矩的角度分析了互联电网的低频振荡。通过在强互联与弱互联系统中阻尼转矩的比较，揭示了弱互联系统中的区域联络线阻抗大幅度削弱系统阻尼的机理，随后相关结论在全国联网系统中得到了验证。文中的研究表明加强电网之间的联络是解决低频振荡问题的最根本的手段。最后，还介绍了阻尼矩阵的概念，并重新在两机系统上推导了其解析形式。文中通过对多机系统阻尼系数矩阵的分析还得知：在系统互联的情况下，考虑一个系统的电磁阻尼时，不仅要研究本系统的模型、参数，还要考虑联络线路阻抗以及参与互联的其他系统模型参数对本系统阻尼的影响。

THE IMPACT OF WEAK INTERNECTION OF BULK POWER GRIDS TO DAMPING AND DYNAMIC STABILITY OF POWER SYSTEMS

The interconnection of national power grids in China brings new issues into power system stability and control especially low-frequency oscillation. In this paper, we analysis the low-frequency phenomena from the viewpoint of damping torques. First, damping torques of strong and weak connected systems are compared, and the results show that the relatively large impedance of tie-lines in weakly interconnected systems could greatly reduce the damping of these systems. Then, this conclusion is validated by tests in national grids of China. These tests also demonstrate that reinforcement of the connection between two bulk power grids is an effective way to mitigate oscillations in systems. Finally, we introduce the not well-known concept of damping coefficients matrix and re-deduce its analytical forms in a two-generator system, then it is concluded that damping of a power system not only depends on models and parameters of the system itself, but also depends on reactance of tie-lines, as well as parameters of other systems participating in interconnection with this system.