Operation Simulation Of Multi Distributed Generations Connected To Power Grid And Application Of UPFC In Hefei Power Grid

Distributed generator(DG),Voltage source converter-high voltage direct current transmission(VSC-HVDC),and Unified power flow controller(UPFC)technologies are the most promising hotspots in power system today.They have important engineering application values and will play an indispensable role in the future construction of smart grids.The research content of this paper is mainly divided into three parts: the operating characteristics of the grid-connected system with multi-type distributed generators,control strategy based on VSC-HVDC system,and the application of UPFC in Hefei Power Grid.Firstly,the operating characteristics of the grid-connected system with multi-type distributed generators were studied.Based on the Matlab/simulink software platform,a grid-connected system with multi-type distributed generators was built and different types of distributed generators control strategy in grid-side converter were designed.Under different engineering conditions,the simulation was verified the safe and stable operation capability of the system.On this basis,the transient stability of the system is studied when the induction motor is started and the three-phase short-circuit fault is occurred.Secondly,the control strategy of VSC-HVDC system was studied.It is clear that at least one converter station must adopt constant DC voltage control.On this basis,the PV system which is connected to the power grid through a VSC-HVDC system was studied,and a coordinated control strategy between the PV grid-connected converter and the converter stations of the VSC-HVDC system was designed.Aiming at the problem of system switching between grid-connected and island operating modes,a smooth switching control based on controller state following was designed,which greatly improves the reliability and economy of power grid operation.Finally,application of UPFC in Hefei Power Grid was studied.The first section analyzed the topology and technical principles of UPFC.Then according to the load characteristics of Hefei Power Grid,the problems of uneven distribution and over-limit of power flow in Hefei Power Grid were comprehensively analyzed.Combine with the specific situation of Hefei Power Grid to carry out the site selection and installation of UPFC.Based on the above work,a Hefei power grid simulation model with UPFC was built to verify the power flow control effect of UPFC.