Analysis On Influence Of HVDC To Transient Stability Of AC System

With the development direction in our country which is "west-to-east power transmission,power exchange between south and north,nationwide interconnection",power system developed more and more fast.HVDC become much more important in power system as it works very well in long distance and large capacity transmission.When HVDC supply power to power receiver system,it will consumption reactive power which is 40～60%of HVDC power.So the stability of AC system which is connect to HVDC will be more and more important.And if we want to ensure the safe operation of power system,we have to do many researches on the transient stability and safety of AC/DC system.This dissertation first introduced the basic structure and working principle of HVDC control system,and analysis different control mode of HVDC converter,and also do some research about the mathematical model of AC/DC power flow,analysis the different algorithm of AC/DC power flow.Then do Some researches about the stability of AC/DC system,analysis the relationship between short-circuit and system intensity,studied the influence to AC system in different control mode of HVDC,and also analysis the relationship between voltage stability and angel stability.At last,with the simulation mode,we do some simulation research in different situation of AC/DC system,such as steady operation,three-phase short-circuit in ac system,dc power reverse and dc block.The simulation results proved the transient stability analysis of AC/DC system,and from the results we knew the severity of different faults to stability of AC/DC system,and at last put forward some suggestions about how to keep the stability of AC/DC system when the faults come out.