Novel Excitation System Based On Full Controlled Devices Rectifier

With the development of power system, the appearance of long-range heavy duty transmission lines, as well as the widespread use of fast-response excitation system, the damping of the entire interconnected power system continuously decreases. And it is likely to induce large-scale inter-regional power oscillation, which will seriously affect the stable operation of power system. Among these measures to damp the low frequency oscillation, the excitation control is one of the most effective and economic measures. Combined with the development of power electronics technology, the dissertation presents a novel self shunt excitation system based on full controlled devices rectifier and systematically studies the novel excitation system, including the issue of theoretical analysis, mathematical modeling, control strategy and simulation analysis. And based on 1000kV Jindongnan - Nanyang - Jingmen UHV AC pilot demonstration project, the dissertation studies the novel excitation system damping the low frequency oscillation.The dissertation describes the principle of the novel excitation system in detail, and presents the topology of VSC and CSC, and researches topology structure and control strategy. Moreover, the mechanism of the novel excitation system improving the damping characteristic of power system damping is studied. The dissertation focuses on the novel excitation system based on VSC. According to external characteristic of reactive power, the reactive power model of excitation system is equal to STATCOM. Aiming at equivalent model, the mathematical modeling of the single-machine infinite bus system is derived. Because the state equation has two control variables, namely, excitation voltage and reactive power, the coordination control strategy uses optimal control theory.Based on the model of the single-machine infinite bus system, control parameters are computed in MATLAB. The dissertation models the power flow modeling and transient modeling, and has several simulations using the novel excitation system and conventional shunt excitation system (with PSS), which include generator for a 5% increase in the reference voltage, three-phase fault at the terminals of generate and switchover operation of single and double circuit transmission lines. The simulation results show the dynamic performance of the novel excitation system is superior to conventional self-shunt excitation system.Selecting 2009 Operation mode of Central China Power Grid, the dissertation studies the dynamic performance of the novel excitation system in multi-machine power system. According to the oscillation mode of units in Central China Power Grid, it selects units which are strongly related to the power oscillation of UHV lines. When 500kV line of power system strongly fault, 2009 Operation mode of Central China Power Grid simulate, which these units use the novel excitation system and original shunt excitation system simulated. Analyzing the power oscillation of UHV lines of the simulation, the result verify that the new excitation system can effectively damp power oscillation of interconnect system, compared to conventional self-shunt excitation system.