Research On Low Voltage Ride Through Technology Of Direct Drive Wind Power System Based On RTDS

With the rapid development of the social economy,environmental pollution and energy shortages have become increasingly prominent.As a clean and safe new energy source,wind energy has received the attention of governments and investment institutions.The application of wind power in the world is more and more extensive,and the stability requirements of the grid for the operation of wind farms are becoming higher and higher.Low voltage ride through(LVRT)is a very important technology in wind power grid connection.When the grid voltage fault falls,the wind turbine must not only keep the grid connected,but also provide a certain amount of no to the grid.Power,maintain system power balance,and support grid voltage recovery.Based on the research of grid-connected wind power system and low voltage ridethrough technology in power grid faults at home and abroad,this paper first analyzes the principle of each part of wind power system structure,and systematically establishes wind turbine and direct drive permanent magnet generator.Mathematical equations for dual PWM converters.Then,the wind turbine pitch control strategy,the motor-side converter control strategy and the grid-side converter control strategy are studied respectively.Each part of the control system is established by the corresponding control strategy to ensure the stability of the system power when the wind power system is connected to the grid.Secondly,based on the grid-connected operation of wind power system,a wind power system based on RTDS real-time digital simulation platform and grid transmission line system are established to build a complete wind power grid-connected system model.Through the simulation experiment,the characteristics of the main node power parameters are analyzed,and the running characteristics of the wind turbine and the simulation parameters set by the model are compared to verify the accuracy and feasibility of the model.Finally,through the analysis of the system voltage,current change and power imbalance caused by the voltage drop of the grid,hybrid control strategy of the gridside converter control based on the static synchronous compensator(STATCOM)and the DC bus increase the Crowbar protection circuit when the grid voltage is deeply dropped are studied.Through the RTDS real-time digital simulation platform for modeling and analysis,the accuracy and feasibility of the STATCOM control strategy of the grid-side converter and the DC bus protection circuit of the DC-bus protection circuit are verified.