With the increasing increase of load in power grid

the contradictions between the demand for improving power flow distribution and scarce power construction land has become increasingly prominent.To maximize the power supply capacity of the grid

more and more unified power flow controller（UPFC）projects are constructed and operated;therefore

the control effect of UPFC device is increasingly important. In this paper

the following work has been done with combination of related study both at home and abroad. Firstly

the typical model（ that is dual voltage model） and corresponding control principle of UPFC is introduced

then

the relationship between the current and voltage at the two ends of the UPFC by using the method of double port network in circuit theory is analyzed and the issue of interaction between the controllers is pointed out. After that

the optimal control strategy is classified and described and

at the same time

the optimization result of various methods and problem existence are briefly analyzed.Finally

the possible study direction of UPFC control technology is listed.