| In recent years,in order to improve the transmission ability and realize power flow controllable operation,the regional power in china grid is rapidly emerging as a interconnected AC/DC power system.The appearance and the application of High Voltage Direct Current(HVDC)and Unified Power Flow Controller(UPFC)have created favorable conditions for modern AC/DC power system.On the one hand,HVDC technology had been developed and applied in real power systems due to its distinct advantages in the aspect of long-distance and large-capability power transmission.On the other hand,UPFC attracted widespread attention and studied as the most creative and most powerful FACTS devices.However,with the serious probability of coupling between the AC and DC power system,the stable and efficient operation of modern power system put forward higher requirement for depth analysis of the interaction between the HVDC and UPFC.The study of this paper can be divided into the following parts around this question:Firstly,the thesis introduces the basic structure,mathematical models and control methods of HVDC and UPFC,and then built the proper model used in this paper of a multimachine power system installed with HVDC and UPFC,get the differential equations,algebraic equation and output equations that can describe the AC/DC interconnected power system.Secondly,The basic principle,property,evaluation criteria and the resolved and unresolved difficulties of relative gain array(RGA)were introduced.And the RGA calculating formulas in the aspect of power system interaction assessment are deduced.Thirdly,the corresponding relative gain array were calculated when the work status of plow flow changes for the actual example of Jiangsu power grid.The calculation results found out the weak interaction between the DC transmission line and UPFC controllers,and this viewpoint verified by the nonlinear time domain simulation. |
