Research On The Twelve-sector Direct Torque Control Of Interior Permanent Magnet Synchronous Motor

Under the background of energy constraints,environmental pollution and so on,the development of electric vehicles has shown an unstoppable trend.In permanent magnet synchronous motors which are high-efficiency and high-power density make them more suitable to provide power for powering electric vehicles.Therefore,it is becoming increasingly important for synchronous motors to find high-performance speed control methods.Different from the vector control strategy,the direct torque control method is not easily affected by the change of the motor parameters,and the dynamic response of the electromagnetic torque is excellent.It does not require cumbersome coordinate operations and transformations,thereby simplifying the structure of the hysteresis controller.However,in the conventional six-sector direct torque control method,the hysteresis controller is used for the control of the electromagnetic torque and the stator flux.Therefore,there are many disadvantages,that is,the torque and the flux pulsation are too large,and the switching frequency of the inverter is not constant,so interior permanent magnet synchronous motor direct torque control method needs further development and improvement.In the traditional six-sector direct torque control method,the zero-voltage vector is not used to control the torque and the flux linkage.This paper quantitatively analyzes the control mechanism and effect of the zero-voltage vector on the torque and flux linkage respectively.A comparative simulation study was conducted under a well-established system simulation model.The simulation results show that the direct torque control method based on zero-voltage vector has the effect of reducing torque and flux linkage ripple.This application of the zero-voltage vector in the direct torque control method indicates the direction.Consider these issues that the traditional six-sector direct torque control method does not add zero voltage vectors to the voltage vector switching table and the disadvantage of excessive torque ripple that may be caused when the flux vector is at the sector boundary.The twelve-sector direct torque control in this paper is based on maximum utilization of available voltage vectors,which refines the vector selection and the sector division,increases the number of voltage vectors to be selected,and effectively takes full advantage of the voltage vectors on controlling the flux and torque;Moreover,comparing and analyzing the control effects of three sector subdivision methods of six-sector,twelve-sector,and eighteen-sector direct-torque control for interior permanent magnet synchronous motors on the flux linkage and torque trajectory,and given the follow-up of the input signal and the immunity to the disturbance input signal are compared in simulation.Three different sector subdivision methods are applied to the dynamic performance of the control system.The simulation results verify that " twelve-sector sectors and eighteen-sectors method can improve the correctness of the asymmetry of the voltage vector on the torque and flux control effects",and also obtains good dynamic performance of the motor under the action of the twelve-sector and eighteen-sector methods.The eight-sector method has the largest number of switching operations,and has a higher requirement for switch tubes.Finally,a detailed simulation on Matlab/Simulink platform compares and studies twelve sectors based on zero-voltage vectors and six-sector methods based on zero-voltage vectors,that is,simulations of stator current,torque and flux control effects.In addition,in order to further optimize the control performance of the twelve sectors,the influence of various internal hysteresis error bands on the torque ripple is also studied,and the torque ripples under different internal hysteresis torque error bands are compared through simulations.The simulation results show that the twelve-sector direct torque control method can effectively overcome the current distortion and solve the problem of large flux linkage and torque,while retaining the advantages of traditional direct torque control methods such as fast dynamic response and robustness to motor parameters.In addition,the internal hysteresis error band can further improve the control effect of the twelve sectors,greatly optimizing the torque ripple in the interior permanent magnet synchronous motor twelve-sector direct torque control method.