Analysis and Control of Reactive Power in HVDC Transmission System

The reactive power dynamic characteristics of high voltage direct current (HVDC) system are strongly related to DC control, which has a significant impact on the fault voltage recovery characteristics of the AC system. Therefore, this paper studied the interaction between DC control and reactive power dynamic characteristics and its effect on fault recovery. Firstly, it analyzed the inherent reactive power dynamic characteristics of dc system when the AC system failed, and studied the dynamic correlation among dc current instruction value, ac bus voltage and reactive power exchange volume. On this basis, the deficiency of Voltage Dependent Current Order Limiter (VDCOL) was analyzed, and a new control strategy for controlling reactive power exchange between AC system and converter station was proposed. Finally, the simulation results show that the proposed scheme can improve the fault recovery performance of the system and reduce the probability of commutation failure. It is important to improve the stability of dc transmission system.