Control And Fault-tolerance Operation Of Five-Phase Dual Stator-Winding Induction Generator System

The energy crisis is a global issue,the development of renewable energy power generation systems and improvement energy efficiency can effectively reduce the energy crisis.Wind power as a renewable energy,especially offshore wind power systems,requires generating system with high performance,high reliability,and large capacity.In the aviation power,more-electric/all-electric aircraft uses electric actuator systems instead of mechanical and hydraulic systems to increase efficiency and reliability,this requires that aviation power generating system have the characteristics of large capacity,high reliability,and high performance.For the above two occasions,induction machine has become an alternative solution due to the advantages of low cost,robustness and simplicity.To take advantage of induction generating system,a five-phase dual stator-winding induction generator(DWIG)system is proposed for the above two occasions.Its characteristics are:(1)The rotor is cage-type structure,simple and strong,high reliability;(2)There are two sets of windings on the stator,one is power winding,the other is control winding,and the power winding rectifies the output high-voltage direct current;the control winding is connected to the five-phase static excitation converter(SEC)to control the excitation of the generator;the two sets of windings are independent and have no electrical connection;(3)The five-phase windings can be used to increase the power density of the generator with non-sinusoidal excitation and enhance the fault tolerance ability.Firstly,this thesis studies the basic problems of the power generation system,including air-gap magnetic motive force(MMF)and mathematical models.Secondly,for the requirements of high power density,high performance and high reliability of the above two occasions,the strategies of harmonic injection,instantaneous power control and the fault-tolerant control are developed.The contents are:To meet the needs of different control strategies,the air-gap MMF of the five-phase DWIG generated by multiple frequency excitations currents was analyzed.Again,the mathematical model of the five-phase DWIG in the natural coordinate system was established.Again,the mathematical model of the five-phase DWIG is established in the stationary coordinate system.Finally,according to the rotation transformation matrix,the decoupling of the fundamental and the third harmonic space is achieved,and the decoupled model of five-phase DWIG is obtained in the rotation coordinates.An appropriate control strategy is the guarantee of high-performance of the generating system.Based on the instantaneous power theory,the principle of DC power generation for five-phase DWIG is analyzed,and a control-winding flux oriented control(CWFOC)based on space vector modulation is proposed for the five-phase DWIG.By the injection of the third harmonic excitation to increase the amplitude of the fundamental magnetic field,the strategy of CWFOC with harmonic voltage injection is proposed to improve the power output of the five-phase DWIG.Since the strategy of harmonic voltage injection has no harmonic current closed loop,which exists the error between of the given harmonic current and the required value.A control strategy of CWFOC with harmonic current injection is proposed for five-phase DWIG.Research has shown that both strategies have improved air gap magnetic flux density and improved power output(this system about 11%).The strategy of harmonic voltage injection has a simple structure and is easy to implement,and not affect the dynamic performance of the system,and it can be easily extended to voltage type scheme applications.The strategy of harmonic current injection has the advantages of controllable harmonic currents,good steady-state current performance,but delays the dynamic performance of the system.To improve the dynamic response of the system,based on the instantaneous power theory,the effect of five-phase voltage vector on reactive power and active power is analyzed,and the optimal voltage vector table is given.For the variable speed applications,the control-winding instantaneous power control based on space vector modulation is proposed for five-phase DWIG.The system's control loop is designed and speed information is introduced into the power loop to eliminate the effects of speed changes.To take advantages of the multiphase characteristics,control-winding instantaneous power control with an improved harmonic voltage injection is proposed to improve the air gap flux density and increase its power output.It shows that the control-winding instantaneous power control with harmonic voltage injection belongs to the voltage type scheme,which has a simple structure,simple implementation,and dynamic performance improvement.Due to the static excitation converter is relatively easy to failure,the control law of the open circuit fault of the power generation system was studied for the reliability problem.A fault-tolerant control strategy based on a full-order transformation matrix is proposed.To deal with the problem of different plane couplings,a fault-tolerant control strategy based on virtual variable control is proposed.Based on the definition of reduced-order transformation matrix and virtual variables,the expressions of flux and torque are deduced.The research shows that two kinds of fault-tolerant control strategies can realize fault-tolerant control of open circuit fault,reduce the ripple of the power-winding output voltage,reduce control-winding current,and reduce torque ripple.The strategy based on the full-order transformation matrix has the advantages of simple implementation and good compatibility,only needs to modify the harmonic current given in different open circuit falults.The strategy based on virtual variable control can achieve decoupling control in different planes,so that the torque has a linear relationship with the flux,and good steady-state performance.The research in this thesis promotes the further development of DWIG from three-phase DWIG to multi-phase DWIG.It provides an alternative solution for the application of DWIG in aviation power and wind power generation,and lays a foundation for future research work.