If single-pole faults occur in bipolar HVDC flexible transmission system

the power can be transferred to the normal pole quickly

and the influence of load shedding on the stability of the power grid is reduced. In order to ensure that the power transfer can be successfully completed

firstly

we put forward the feasibility conditions and the process of power transfer; secondly

we established a real-time digital simulation model during the power transfer process

analyzed the electrical characteristics of DC field

and proposed an optimization method of power transfer rate

finally

a designed example was given and the verification tests were conducted at Xiamen HVDC flexible transmission project. The test results show that the direct current rising speed is limited by reactor and cable

so the power can not be transmitted in time and accumulated in the modular multilevel converter

which can lead to DC overvoltage protection action. When the power transfer rate is 500 MW/10 ms

the DC overvoltage Ⅰ segment protection action is caused. When the power transfer rate is optimized by using the numerical valued of 500 MW/60 ms

the power transfer process is successfully completed. Based on the analysis of the electrical characteristics of DC field

the power transfer is successful implemented in a Xiamen HVDC flexible transmission project by optimizing the power transfer rate

which proves the feasibility of control strategy of power transfer process in bipolar HVDC flexible transmission system..