Research On The Influence Of Synchronous Condenser On Voltage Stability Of HVDC Transmission System

The long-distance HVDC transmission system has large capacity and complicated structure.Voltage drop or overvoltage due to fault have a greater impact on the system.When it is serious,continuous commutation failure will be caused,which will affect the quality of power transmission.And the safe and stable operation of the AC system at both ends will face new challenges.The synchronous condenser currently used in converter stations is a new generation condenser.It has the advantages of traditional synchronous condenser,larger capacity,faster response speed and smaller cost.The new generation synchronous condenser has unique advantages in long-distance HVDC power transmission.Therefore,it is extremely necessary to study the effect of synchronous condenser on the voltage stability of HVDC transmission system.Firstly,this paper uses the working principle of the synchronous condenser to establish its mathematical model and analyze its reactive power characteristics.A simulation model of synchronous condenser based on sliding mode variable structure excitation control system was established by using simulation software.Secondly,an IEEE three-machine nine-node AC system simulation model is established in order to verify the dynamic performance of the synchronous condenser and analyze its impact on system voltage stability.Then,a simulation model of the HVDC transmission system is established using simulation software to analyze the reactive characteristics of the synchronous condenser in the HVDC system and its effect on the system voltage stability.In this paper,three working conditions such as symmetrical short circuit fault,asymmetrical short circuit fault and reactive load mutation are set on the AC lines of multiple established simulation models in order to analyze the dynamic response characteristics and reactive power compensation ability of the synchronous condenser,and its ability to support system voltage in pure AC systems and HVDC transmission systems.Finally,in HVDC transmission systems,when the synchronous condenser is put into the transmitting and receiving converter stations,this paper compares and analyzes its dynamic response,reactive power compensation capability,and its ability to support the voltage of the converter stations at both ends of the HVDC transmission system.