The Main Circuit And Control Strategy Of Excitation System Based On Full-controlled-devices

With the operation of Three Gorges Project and the ultra high-voltage lines, the grid of China has been interconnected by cross-country large power systems. In addition, the fast excitation system widely used in large generator has caused continuously decreased damping of the entire interconnected power system, thus the dynamic stability of power system becomes more and more critical, and the most prominent problem is low-frequency oscillations between large areas. Meantime, long-distance power transmission is another feature of China. Yet there is no effective way to ensure the stability of large generators of long-distance transmission. In numbers of ways to enhance the stability of power system, excitation control is considered to be the most effective and economical. In this paper, the novel excitation system based on full-controlled devices has been studied, and analysis of its structure and control strategy of the main circuit is given. Model based on single machine infinite bus system is established, and damping torque is used to test the damping ability of the novel exciting system. Excitation system controller design is discussed and simulation results verified the validity, thus providing a novel solution for low-frequency oscillation suppression and long-distance power transmission enhancement.This paper mainly researched exciting system based on voltage source converter,analyzed characteristics of the main circuits and its control strategy. According to the equivalent model of novel excitation system,the Philips-Heffron model of the single machine infinite bus system is established. Analysis and mathematical expression of damping provided by injected reactive power verified that excitation system based on full-controlled devices can improve power system's damping capacity. The phase compensation method and the linear optimal control strategy are applied to design the excitation controller. Simulations of single machine infinite bus system with the conventional excitation system and the novel excitation system are given. Simulation results show that: Compared with the conventional excitation system, the novel excitation system based on full-controlled devices can maintain the system stability and restrain low-frequency oscillations more effectively. Simulation results also verified that the controller design is reasonable.