| Switched reluctance motor(SRM)has been recognized by the market because of its simple structure,wide speed range and strong fault-tolerant performance,and has become one of the hot spots in the field of modern motor drive.The application of SRM is seriously affected by the disadvantage of large torque ripple.The accurate measurement of torque ripple is the premise of reducing torque ripple.In addition,the power converter is an important part of the SRM control system.When the power converter fails,it will generate a huge phase current in the fault phase and burn out the motor and its control system.When the fault occurs,the torque ripple of the motor will increase obviously.At this time,it is necessary to adopt an effective fault-tolerant operation strategy to reduce the torque ripple of the motor,so that the motor can run stably for a period of time in case of fault.In order to judge the effectiveness of faulttolerant operation strategy,it is also necessary to measure the torque ripple accurately.Therefore,the research on fault detection and torque ripple detection of power converter has great theoretical significance and practical application value.The main contents of this paper are summarized as follows:In this paper,the asymmetric half bridge power converter of SRM is taken as the research object.Based on the distortion of the phase current and the motor speed after the fault,an online detection method of the switch tube short circuit and open circuit of the asymmetric half bridge power converter is proposed.According to the characteristics of phase current spectrum,the concepts of fundamental component eigenvalue and spectral ratio eigenvalue are put forward.The diagnosis of fault occurrence,fault type and fault phase is realized by using spectral ratio eigenvalue.After analyzing the change of speed fluctuation coefficient before and after the fault,the ratio of speed fluctuation coefficient of two adjacent phase current cycles is used to locate the fault components.The fault detection system of power converter is built in the upper computer,and the fault characteristics of phase current and speed are analyzed synthetically to realize on-line fault detection of switched reluctance motor power converter.The results of simulation and experiment show that this method not only has strong anti-interference ability,but also has reliable fault diagnosis results.Without additional sensors,it can detect the fault of power converter on-line,which provides a good condition for fault-tolerant operation of motor.At present,high-performance torque sensor is generally used to detect the torque ripple,but the cost of torque sensor is very high and some applications are not suitable for installation due to space constraints.In this paper,a new torque ripple measurement method and system is designed.The method adopts frequency voltage conversion technology to collect and filter the analog voltage related to the instantaneous speed of the motor.Through the data collection module,the voltage analog quantity is collected at a high sampling rate and transmitted to the upper computer at high speed.The torque ripple measurement is realized by using the upper computer Lab VIEW to build the torque ripple calculation module Now the torque ripple is displayed and saved in real time.The experimental results show that the system has high acquisition frequency,can accurately measure and record the torque ripple of SRM in the operation process,and has strong practicability... |
