Study On Voltage Supporting Effect Of TCSC On Regional Power Grid

In the recent decades, along with the constant increase of electric requirement and the enhanced electric load, the problem of voltage stability in power grid stands out day and day. In the world, accidents, such as electric system breakdown and mass electric power cut, occurred time after time because of the voltage lost stability. Voltage insecurity has bacome one of the primary factors that limit the power transmission. The mathod of enhancing the voltage stability has become a problem which starves for settling.At present, the more commonly used reactive power compensation devices for the voltage stability are shunt capacitor, SVC and so on. However, under some certain disturbances, the excessive use of the capacitor will worsen the reactive power balance, even result in voltage callapse. Different from the shunt compensation devices, the compensation capacity of the sereis compensation devices will not reduce when the system voltage dropping. The series compensation devices adjust the imdepedance of the transmission lines, shorten the electric distance between generators and loads, then affect the system reactive power distribution, thereby improve the system voltage stability.The device of TCSC(thyristor controlled series compensator,TCSC) which is the first applied device of series FACTS devices attracts more and more attention of people. The paper studies the effects of TCSC on the receiving-end grid voltage stability, and obtains certain results.The paper analyzes the mechanisms of the simple-system voltage stability and the receiving-end grid transient voltage stability, raises the feasibility of TCSC in improving the system voltage stability. The paper compares the voltages of receiving-end system under these three cases:no compensation, the same compensation capasity of series compensation and shunt compensation, the conclusion that series compensation devices can improve the system voltage stability can be found by the analysis, the further analysis of P-U curve shows that TCSC can improve the static voltage stability of receinving-end system.The transient mathematical model of TCSC is derived. Taking the transient voltage instability problem in southern power grid in Hunan for example, the effects of TCSC on improving transient voltage stability are simulated, and the results shows that TCSC has a certain function of improvement of the system trasient voltage stability.