| The security and stability control equipment is indeed the second and third lines ofdefence for ensuring the stability and security of power network. Non-fault trippingcriterion is an important part of the criterion of stability control equipment, and it’s also thepremise of accurately judging the system state and correct operation. The existing Non-faulttripping criterion is not perfect, which may cause the stability control device malfunction,and need further research and improvement. When the Tie line tripping, lower voltagepower grid may splitted from the power grid. forming isolated network. However, for110kV voltage levels of power grid, the generator and load characteristics is lack ofeffective testing and assessment, safe and stable operation of small grid rely mainly on thesupport of large power grid, which is difficult to play an effective role in supporting in theisolated network operation state. Therefore, the parameters related to the isolated networkoperation and control measures which ensure the stable operation of the isolated networkneed to be further studied.This thesis firstly study deeply on Non-fault tripping criterion and other operating electricalquantity by using the simulation software PSCAD/EMTDC to simulate various operatingconditions and analysis the electrical quantity variation characteristics. Then analysis andsummary the Non-fault tripping criterion of the stability control device, pointing out thatthe criterion may produce false when load transfer, put forward the correspondingsuggestions for improvement, and studied impedance criterion based on the traditionalcriterion, put forward to improve an opinion misjudgment problem caused by system vibration.And then put forward the corresponding criterion based on the research of transient criterion.Aiming at the isolated network operation problem caused by contact line tripping, thisthesis analyzes the characteristics of isolated network operation, points out that thefrequency control is the key to isolated network stability. And then In-depth study thefrequency characteristics of isolated network operation and factors influencing the stabilityof isolated network frequency. Then, on the isolated network frequency control strategyresearch, in-depth analysis the over frequency generator tripping and low frequency loadshedding measures of the isolated operation. Subsequently, structures of the PSASPdatabase of Shennongjia power grid, developed the Shennongjia isolated grids strategy.Finally, use the power system analysis software package PSASP to check the isolatednetwork stability control strategy. The simulation results show that, according to theformulation of the high and low frequency strategy can guarantee the stable operation ofisolated Shennongjia power grid. |
