Research Of Modeling And Optimized Fault Ride-through Control Of Doubly-fed Induction Wind Turbine Under Grid Fault

At present,because of the energy and environmental problems,renewable power generation is in rapidly developing,wind power one of the most promising way,which get fast development.However,the growth of wind capacity has brought some hidden dangers to the safety and stability of the power grid.In recent years,a number of serious off-grid accidents occurred with large-scale wind power access to the grid in China and abroad.The results show that the operation characteristics of wind power generator,which is based on power electronic equipment,is a problem that must be faced in order to improve the wind power penetration.In this paper,current mainstream wind turbine based on doubly fed induction generator is taken as the research object.Starting with its model,theoretical derivation and simulation analysis are discussed,and the optimal control of doubly fed induction generator under grid fault condition is analyzed.Based on the analysis of the circuit topology of the doubly fed wind power generation system,a detailed electromagnetic transient model of the doubly fed wind power generator is established by using the Matlab/simulink simulation software.Considering the difference of the time constant in different sub modules of the doubly fed induction generator,the sub modules of the full order electromagnetic model of the doubly fed wind turbine are simplified.The simplified model of wind turbine is established in DIgSILENT/PowerFactory,and is simulated under fault condition.The accuracy of the model is verified by comparing with the measured datas.The research about the voltage phase angle jump at the terminal of DFIG under short circuit fault is made.By comparing with synchronous generators,revealing that because of the decoupling of rotor position and voltage phase,it will bring the phase angle jump,which affects the accuracy of phase-locked link in the traditional control of wind turbine,and then the decoupling control of the power is affected.In considering the case of phase can not be locked accurately,voltage phase angle compensation has been added to the rotor voltage control,which brings about a rotor current directly control fault ride-through strategy.For the wind power generation replacing the conventional synchronous generator,the damping control of the doubly fed fan is studied.The existing active power and reactive power damping control scheme are analyzed and summarized in this chaper,consider the capacity limit of the DFIG converter,a damping controller is designed to meet the reactive power support during fault ride-through.It can meet the reactive power requirements in the case of damping power system low frequency oscillation.On the basis of this controller,a coordinated control strategy for fault ride-through and damping control is proposed,by adding active damping control during the recovery of the fault ride-through.Simulation results show that comparing to traditional control strategies,it can reduce the power oscillation in tie-line of the power system,proving the effectiveness of the strategy.In summary,this paper starts from the electromagnetic transient model of doubly-fed wind turbines,which is simplified according to the time scale of the model submodule.Voltage phase angle jump and damping characteristics of power system has been considered under large-scale integration,and the improvement of control strategy has been made.