Research On Fault Tolerant Strategy Of Direct Power Control Of Open Winding Brushless Doubly-Fed Wind Turbine

This dissertation conducted an in-depth study on the fault-tolerance tactics for direct power control of opening-winding brushless doubly-fed wind generator.The main contents of this article include the following four aspects.Firstly,this paper selects the brushless doubly-fed generator as an object of study and analyzes the structural characteristics of its stator and rotor,as well in which elaborates the magnetic field modulating action of the new type of rotor used in the motor,and also explains the fundamental principle of motor operation and its energyflow under different operating conditions.The mathematical model of OW-BDFG in different coordinate systems are established respectively and no-load simulation analysis are conducted by MATLAB in this paper.The simulation results are gained,which proves the correctness of the theory.Secondly,it mainly analyzes that the feeding operation topological structure of the double-level converter in the isolate the DC bus which is used by the brushless doublyfed wind turbine with open winding.On this basis,the brushless doubly-fed generator is analyzed and studied under the direct power control strategy.Considering that the switching tubes of the IGBTs on the converter are prone to failure in actual operation,this paper put forwards a fault-tolerant control strategy that centered on the direct power control and analyzes the influence of open circuit fault of power switch device on the system,then obtains the voltage space vector synthesis distribution of the control winding after the fault.According to the basic principle of direct power control and the fault types of power switching devices,the voltage space vector is optimized and combined.Thus,the optimization table of voltage space vector is obtained,which makes the system can continue to run under failure according to the reconstructed switch table.Thirdly,sliding mode control(SMC)is used to optimize the control of power in the system,replace the original lookup table scheme with SVPWM voltage modulation control technology to fix and enable switching frequencies.and effectively reduce fluctuation of active power and reactive power and switching loss,And increase the Model Reference Adaptive System(Model Reference Adaptive System,MRAS)as a speed observation to replace the speed sensor,and it can not only have good tracking performance when load disturbances and speed changes,but also improve the reliability of the system.Finally,The simulation models of direct power control with look-up table method and SMC and MRAS are established respectively,array simulation of the above three models,comparative analysis of simulation results,prove the correctness and feasibility of the adopted sliding mode variable structure control and the improved direct power control system without speed sensor technology,the system has better running status and robustness,when the system is in single and two IGBT failures,the system can still achieve variable speed constant frequency and constant voltage generation operation in super-synchronous,synchronous and sub-synchronous modes,and the deviation of active and reactive power can be controlled within ±200W and ±200var,the harmonic distortion rate of the system in the three asynchronous speed modes can be as low as1.47%,1.37%,1.35%,1.34%,1.22%,1.15%,the system has better features.