Research Of Direct Torque Control For Six Phase Induction Motor

With the development of power electronic device and digital signal processing chip, the speed regulation technology of three-phase ac motor has been greatly improved. The speed regulation system of the multiphase induction motor has made great advantages compared with the speed regulation system of three phase ac motor, such as high reliability, high power but low dc power and low electromagnetic torque ripple, obtaining a middle or high power drive will bring about voltage-sharing or current-sharing problem of the power device in series or parallel circuits in the restricted circumstance for the voltage of power supply. Recently, the application of speed regulation system of multi phase motor focuses on military and high reliability, high power situations, ship propulsion system and so on.This paper chooses dual three-phase induction motor as the object of study, according to the coordinate transformation theory, the decoupling coordinate transformation matrix from six phase natural coordinate system to two phase stationary a/3coordinate system is derived in this paper firstly, and the math model on the a/3coordinate system is established based on the decoupling coordinate transformation matrix, meanwhile, the equation of stator and rotor flux linkage, voltage, current and motion are introduced.Secondly, the voltage space vector distribution of dual three-phase voltage-source inverter is introduced, and the traditional six phase SVPWM modulation arithmetic is analyzed based on three phase SVPWM modulation arithmetic, moreover, six phase SVPWM based on zero sequence balance is designed and central processed, in addition, the effect of the voltage space vector to electromagnetic torque and stator flux is analyzed in detail, at the same time, introducing simply the fundamental principle of direct torque control and designing a direct torque control system based on six phase zero sequence balance SVPWM modulation arithmetic.Besides, according to the equivalent principle of magnetic motive force, the coordinate transformation and math model under one or two phase stator windings defaulted of dual three-phase induction motor is deduced in this paper, meanwhile, the rotor field oriented vector control system aimed at the dual three-phase induction motor under one or two phase stator windings defaulted is designed based on the virtual synchronous rotating coordinate transformation.Under the MATLAB/Simulink simulation platform, the simulation models of the direct torque control system based on six phase zero sequence balance SVPWM modulation arithmetic and the rotor field oriented vector control system aimed at the dual three-phase induction motor under one or two phase stator windings defaulted are built, the simulation results are analyzed in detail and also verify the correctness of the designed control system in this paper.At last, the digital signal processing chip TMS320F28335produced in Texas Instruments company is used as the main control chip in the hardware experimental platform, the control circuits per section are designed in the platform, according to the flow chart of software system about direct torque control system based on six phase zero sequence balance SVPWM modulation arithmetic, the corresponding control algorithms are programmed in the CCS3.3software development platform by using C language, and the program debugging is performed based on the hardware circuit, the experiment results testify the effectiveness of the direct torque control system, which makes a full preparation for the follow study.