The recent research shows that the reactive power control is one of the important means to improve the transient stability of VSC-MTDC system. However

the transient stability control effect of current reactive power control is weak due to communication delay. In view of this

the transient reactive power control strategy of communication-free based VSC-MTDC system is proposed in this paper. The strategy makes full use of the local auxiliary active power modulation information in the control of voltage drop of DC side. Only local measurements are needed to estimate the global frequency weighted value

and the frequency weighted value is used as the reference value of auxiliary reactive power control in converter station for the purpose of control. The proposed control method is simulated and verified based on PSS/E.The result shows that the control strategy performance of the method is very close to that using the global measurement information

which can improve significantly the transient stability of the system.