Research On The Effect Of Dual-Excited Synchronous Condenser On The Voltage Stability Of AC-DC Transmission Systems

With the development of China’s ultra-high voltage DC transmission system,new energy sources on the grid,and increasing power electronics,China’s power grid urgently needs to solve the problem of large-capacity dynamic reactive power reserve.At present,China has already installed a certain number of synchronous condensers in the converter stations of UHV DC transmission system.Since the synchronous condenser has only one set of excitation winding,the stable operation range is limited,and the reactive power absorption needs to be restricted during the in-phase operation,otherwise instability is likely to occur,so it is necessary to study the model about the new generation of dual-excited synchronous condenser and their operation characteristics.In this paper,a new generation of dual-excited synchronous condenser is used to study its effect on the voltage stability of AC-DC transmission system.Firstly,the electrical structure of the dual-excited synchronous condenser is explained,its basic operation principle is analyzed according to the principle of motor science,its power regulation process is analyzed by using vector diagram,and the mathematical model of the dual-excited synchronous condenser is established to lay the foundation for the subsequent model establishment.Secondly,in order to achieve the purpose of maintaining sufficient reactive power reserve at steady state and fast dynamic reactive power output at fault of the dual-excited synchronous condenser,the control strategy of slow reactive power outer loop and fast voltage inner loop superposition is adopted to provide a method for the practical application of the dual-excited synchronous condenser.And the validity of the model is verified by its access to the single infinity system,and the operating characteristics of the dual-excited synchronous condenser at steady state are also analyzed.Finally,in order to analyze the effect of dual-excited synchronous condenser on the voltage stability of the AC-DC transmission system,an AC-DC transmission system containing dual-excited synchronous condenser is established.Using the established AC-DC transmission system,we analyze the effect of adding dualexcited synchronous condenser,synchronous condenser,and no reactive power compensation equipment on stabilizing the system fault voltage when the system has short-circuit fault,voltage fluctuation,and phase change failure,and derive the advantage of dual-excited synchronous condenser on improving the voltage stability of AC-DC transmission system...