Study On Grid-connected Control Strategy For Permanent Magnet Directly Driven Wind Power Generator System

In recent years,the global environment and resources shortage problem increasingly serious,the development of new energy is becoming more and more important.Wind power,with its unique advantages,is becoming an important part of the energy structure in the development and utilization of new energy.With the expansion of the scale of wind power,the impact of wind power system for grid cannot be ignored.High power permanent magnet direct drive wind power system,with the advantages of flexible control of active,reactive power,low speed,high efficiency,i.e.is one of the most prospect of wind power generation system.This article mainly centered on the permanent magnet direct drive wind power system interconnection control related technology research.Control strategy is designed respectivelyon Wind turbine side and grid side for the system,and sliding mode control is introduced,which improve the wind power system control performance.As the same time,wind power system interconnection technology of low voltage through has been studied,permanent magnet direct drive wind power system can work in safe operation in the case of grid side failure.The correctness of theoretical research has been verified through the way of simulation.Firstly,the overall structure of the corresponding wind turbines and converter topology are determined.Wind turbines and generators is established corresponding mathematical and simulation models,the mathematical model of converter is analyzed,the permanent magnet direct drive wind power system control scheme is identified.Secondly,the implementation of the control system of generator side is tudied,for the purpose of maximum power tracking on the generator side,optimal tip speed ratio method is taken.and permanent magnet synchronous generator model is verified analysis;Working principle of SVPWM technology is studied,based on this,generator side converter control strategy is put forward,which provides theoretical basisand simulation platform for subsequent research.Thirdly,the implementation of the control system of generator side is studied,with voltage oriented vector control applied,double closed loop PI control analyzed,the phase lock loop realized,and grid-side bus capacitance and filtering inductor selected;On the basis,sliding mode control is introduced into PI inner loop of the current control and the corresponding sliding mode controller is designed;On the basis of voltage oriented vector control of grid converter,Simulation and mathematics model of double closed-loop PI control and sliding mode variable structure control are respectively set up,the superiority of the sliding mode variable structure control is verified.Which provides a great simulation platform for the research of low voltage through strategy when connected to grid-side.Again,low-voltage ride-through technology of the permanent magnet direct drive wind power system is studied,low voltage power grid through control strategy of three-phase symmetrical fault is mainly researched.Crowbar protection circuit and grid side reactive compensation strategy are designed,then the logic implementation of the project of low-voltage ride-through is analyzed.Finally,in the toolbox of MATLAB/Simulink,Grid-connection control strategy model for simulation,great operation effect are respectively validated on the case of the normal and symmetrical grid fault in the power grid.The applicability of the grid-connected control strategy of wind farms and the superiority of the sliding mode variable structure control are shown in the simulation results.