The flexible DC reactive power component can choose constant AC voltage control and constant reactive power control

and the constant reactive power control is normally adopted in the converter station.The dispatcher may order to emit or absorb the reactive power through the flexible HVDC to regulate the AC voltage to the target value. However

the dispatching instruction is in general AC voltage target value

for which the voltage regulation is achieved by the converter station through multiple reactive power remote adjustment. This not only increases the operation risk at site

but also brings multiple reactive power and small voltage perturbation of the system. In this paper

a kind of Two-step voltage regulation method is proposed. The first step is to test the short circuit capacity level of the system

while

the second step is to calculate the amount of reactive power precisely in accordance with the capacity level of the present system

thus achieving the quantitative regulation of reactive power control of flexible HVDC converter valve to the AC voltage. The method

throughout the two-step voltage regulation

can meet accurate voltage regulation requirement without real time calculation of the capacity of the grid system

and is simple and practical.The effectiveness of the method is verified through PSCAD/EMTDC off line simulation and the in-the-loop simulation test of control & protection equipment hardware based on RTDS.