Study Of SRM Sensorless Control System Based On Current Waveform Detection Method

Switched reluctance motor is a new reluctance motor with such advantages as simpleand strong structure, wide adjustable speed range, high efficiency and high reliability. Ithas received extensive concern since it appeared. The switched reluctance motor cannormally run depending on the accurate information of rotor provided via the physicallocation encoder, which increases the cost and complexity of the structure of entire motorspeed control system. In addition, because the position encoder can’t normally work in theharsh industrial environment, the application range of the motor is limited to a great extent.As a result, it is very necessary to consider how to make the motor normally run withoutthe position sensor. Therefore, it has become a hot domain to research the sensorlesstechnology of switched reluctance motor.In this study, the current gradient detection method without sensor control isemphatically introduced with its detection principle as well as advantages anddisadvantages being analyzed. On the basis of the current gradient detection method, anew sensorless detection method--current waveform detection method, is proposed, whichdirectly detects the magnitude of phase current. Through comparing of the magnitude ofcurrent, the maximum current of the conduction phase is obtained and thus the initialoverlap position between the minimum area and the rise area of inductance is determined.With current waveform detection method, the problem of failure of the sensorless currentgradient method due to low speed is resolved. Through the theoretical comparison of thetwo methods, the method for determining the opening and closing position of conductionphase is put forward by using the pulse counting method; and the issue on the rotate speedestimation lag in the current waveform detection method compared with the currentgradient method is resolved. Then, the simulation model for sensorless current waveformmethod is developed with BLDCM MATLAB software, and the simulation analysis forthe system is conducted. The simulation results are consistent with the theoretical analysis,which verifies the Current waveform method can more accurately estimate the rotorposition. And meanwhile, the motor can steadily run under the conditions of constant rotate speed and sudden changes of rotate speed and load torque by using the currentwaveform detection method. Finally, the experimental platform is built. With the digitalsignal processor TMS320F28335as controller, the experimental verification and analysison some basic control modes and current double closed loop system of the switchedreluctance motor, and proposed current waveform detection control system are carried out.The experimental results prove that the current waveform detection method enables themotor run normally under the constant rotate speed.