Direct Torque Control And Implementation For Brushless Doubly-fed Machine

The development history and research meaning of the brushlessdoubly-fed machine (BDFM) and the development of the modern controlsystem of AC motors are sketched. The operation principle, variousoperating mode and power flows under the doubly-fed mode of operationare analyzed that provide a theoretical basis for motor control. The d-qmathematical model is deduced which based on the network mathematicalmodel, then the simulation model of BDFM is build with theMatlab/simulink,and the open-loop characteristics simulation of variousoperation mode and power operation under the light condition are carriedout that verified the applicability of the BDFM mathematical model andtheoretical analysis of the consistency. Two actual application problems ofthe harmonic wave in the power grid and motor’s highest operating speedare analyzed in the open loop condition. All kinds of defects are putforward in the control of the open-loop, the meaning of closed-loop controlis significant.The direct torque control of the BDFM is focused on the speed controlprinciple, the control winding magnetic chain vector and its voltage emptyvector relationship is clarified through mathematical analysis method, andthe six sector circular magnetic chain control process is expatiated, how todetermine the sector and choose the best voltage space vector method arepresented. The direct torque control system simulation model is establishedBased on constructing u-i magnetic chain model, and the good performanceand deficiency of the direct torque control of the BDFM are analyzed, thevoltage space vector is how to influence the magnetic chain is explained.The inverter switch state is based on the torque error and the statorflux amplitude error in the hysteretic controller which is adopted on thetraditional direct torque control for the brushless doubly-fed machine,inthis way,current and flux are distorted that results torque ripple in lowspeed range,even more influents control effect of the wholesystem.According to this problem,a new direct torque control method withfuzzy-PI regulator for the brushless doubly-fed machine is presented in this paper,applying the fuzzy theory to design controller parameters.Thesimulation results show that the method is effective to improve the dynamiccharacteristics of the motor,reduce the torque ripple,improve the speed andthe torque control precision,expand the direct torque control system ofspeed range.It’s how to realize in DSP that the direct control of the BDFM isstudied. The entire speed control circuit is designed, and the program isdesigned modularization. Some programs are debugged successfully, andsome of the staged achievements are obtained.