Study On Active And Reactive Power Control Of Wind Farm Connected By VSC-HVDC

In recent years,the issue of energy shortage has become increasingly tense,which has established an excellent platform for the development of new energy.In particular,the development of wind power generation is particularly rapid.Its scale has been continuously expanded,the installed capacity has been continuously increased,and the transmission distance has increased.This has led to the increasing influence of wind turbines on the voltage stability of the power system,which affects the voltage stability.Mainly manifested as : the lack of reactive power in wind farms,the high charging power of submarine cables,the complexity of wind farms in grid-connected mode,and the incompleteness of reactive power compensation strategies,and the impact on the grid point voltage and the neighboring grid.Therefore,the analysis of reactive power characteristics of grid-connected wind farms,especially reactive power compensation strategies,has extremely important practical significance.The main work of this paper is as follows:(1)Starting from the most widely used model at present,this paper takes the double-fed induction fan(DFIG)as the main research object,and establishes the mathematical model of wind turbine and wind farm.The established mathematical model includes: DFIG model,current collection system model,transmission system model.Finally,the reactive power characteristics of each module and its corresponding control method are analyzed to provide a reliable basis for the subsequent development of a reasonable control strategy.(2)The voltage stability research methods are introduced in detail,mainly including static analysis methods and dynamic analysis methods.After a comparative study of the static characteristic curve analysis and the commonly used static analysis method,this paper adopts the continuous power flow method to draw the PV curve static analysis voltage stability.For the dynamic analysis method,time-domain simulation is used to plot the voltage curve over time,and the transient stability of the voltage is studied.(3)Establish wind farms to access the system model of CIGRE B4-39 through a flexible DC transmission system(VSC-HVDC),and propose the use of VSC-HVDC to coordinate the wind farm side,the wind farm side,and the fan rotor side converters.Reactive power control strategies and optimization analysis.(4)Study the active power control strategy for grid-connected DFIG wind farms.The article improves the DFIG active power control strategy for grid side faults.In order to reduce the active power output of the wind farm and the voltage stability of the DC bus,comprehensive consideration is given to the VSC-HVDC DC line voltage fluctuation as a signal.(5)Based on the model established in this paper,simulation calculations are made from the perspectives of control strategy and different fault depths of the wind farm fan network points.Through analysis,it is concluded that a reasonable reactive power control strategy is consistent with the reactive power of the wind farm grid-connected system.Power compensation requirements can not only effectively reduce the compensation equipment,save system cost,but also improve the system’s voltage stability and active balance.