Research On Control Strategy Of Double PWM Converter For Full Speed Squirrel Cage Asynchronous Wind Power Generator

Compared with other wind power generator,squirrel-cage induction generator has the advantages of simple structure,high reliability,strong maintenance and low operation cost,high power density.Wind power generation applications in thousands of kW,the use of squirrel cage asynchronous generator is an option worth considering.At present,squirrel cage asynchronous wind power generator system is a new technology and its technology is not mature.In order to improve the reliability of the wind energy conversion efficiency of squirrel cage induction wind generator system,three control strategies for double PWM converter have been researched in this paper.Firstly,on the basis of analyzing the mathematical model of squirrel cage induction generator system for wind turbine,the squirrel cage induction generator,PWM converter,rotor field oriented control strategy of squirrel cage asynchronous generator and grid voltage oriented control of grid connected inverter dual PWM converter control strategy have been researched.With the off-line simulation and physical experiments,voltage buildup characteristics of the squirrel cage induction generator and integration characteristics of dual PWM converter have been analysised.Considering Vector control based on dq rotating coordinate system for squirrel cage induction generator and grid connected inverter,this paper presents a new method which uses rotor flux orientation for squirrel cage induction generator and virtual flux oriented control strategy with abc natural coordinate system for inverter.There is no need for coordinate transformation.Respectively,offline simulation and experiment has been done,and vertify that the natural coordinate control saves operation time compared with traditional dq rotating coordinate vector control.In order to reduce the dependence on the control strategy of generator parameters and current loop control,this paper studies the control strategy of direct torque squirrel cage induction generator based on SVPWM,carried out off-line simulation and experiment.the experimental results verify the validity of the control strategy.Compared with vector control,the stator resistance parameter is only needed which enhances the robustness of the system.Finally,hardware in the loop experiment has been done by combining Q8 system which runs the mathematical model of squirrel cage induction generator and PWM converter with TMS320F28335 DSP.Respectively for squirrel cage asynchronous generator rotor field oriented control and grid connected inverter based on virtual flux of natural coordinate system,C code of DSP for digital realization has been written.