Research On Control Of Flexible HVDC Transmission System With Distributed Generation Unit

In the September last year, general secretary Xi Jinping delivered an important speech at the General Assembly Development Summit, initiative to explore the construction of the global energy Internet, to promote clean and green way to meet the needs of the world's electricity. New energy will play an important role in the future electricity supply. It is important to study the control mode of distributed power supply access flexible DC system to ensure the safe and stable operation of power system and the way of distributed generation.In this paper, the control of the flexible HVDC transmission system is studied, including the following aspects:(1) Analyzed the advantages of flexible DC transmission technology in the local application of distributed power system, and then introduces the MTDC system advantages and broad application prospects;(2) The basic function module of HVDC transmission:the working principle and operation characteristics of voltage source converter VSC are analyzed;(3)The mathematical model of flexible HVDC transmission is calculated, and the relationship between the control system and the controlled quantity of the flexible HVDC transmission system is determined according to the mathematical model and the constraint conditions of the system stability;(4) In order to control the linear aspects of active control, reactive power control, system, on the basis of cascade PI (proportional integral) control method, feedback linearization method and inverse system method to build a network of VSC is connected with the active control logic unit and connected to passive network VSC control logic unit.(5) Based on the analysis of the two terminal HVDC model, the multi terminal DC transmission are analyzed, research the master-slave control and voltage drop control of the two control method is applied to multi terminal HVDC transmission system, which is established by using master-slave single point DC voltage control of three terminal DC transmission the system, use the Simulation software PSCAD/EMTDC simulation generated by the test and analysis, simulation results show that the control method has good dynamic stability and steady-state control accuracy, indicating that the VSC-HVDC System Model in this paper has good flexibility and reliability of power supply.