Position Sensorless Drive System For Switched Reluctance Motor

Switched Reluctance Motor(SRM) has the advantages of reliable structure, low cost for the system, high efficiency and flexible control, which is promised to have a great potential for application in many areas. To achieve better performance, the feedback of position information is unavoidable. However, the traditional position sensor not only increases the cost and complexity of the system, but more importantly it also reduces the reliability of the whole system, thus making the biggest advantage of SRM no longer outstanding. So how to realize the sensorless technology has become one of the most important research projects in switched reluctance drive system.This paper gave a detailed discuss about the structure of SRM and the essence control strategies, then analyzed two frequently used closed-loop control structures. One was made up of speed-loop outside and current-loop inside, and the other was based on the thought of micro-step control theory to divide the rotor angle into three different section, in which the torque of each phase was directly controlled to restrain the fluctuation of torque. It was modeled in Matlab/Simulink, which agreed with the theoretical analysis and proved it was useful in depressing the wave of the torque in SRM.This paper studied the sensorless methods, and made an analysis about the advantages and disadvantages. The Simplified Flux Method was considered. The moment at which the phase was changed was found by comparing real-time calculation of flux linkage and the pre-stored flux linkage data, then the speed and the position information were obtained through these moments. This method had high precious effect in angle identification when the speed was stable. To solve the angle problem in low-speed, the High Frequency Signal Injection was brought in. This method made use of the variation trend of the stator’s inductance to decide which phase to turn on and which phase to inject high frequency signal by comparing the motivated current by injection signal with the two pre-settled thresholds. And such kind of circle control could solve the problem of identification at low speed. It was validated by simulations.The 675 W driving system, and its inverter part adopted the most commonly used asymmetric structure.The magnetic particle brake was used to set up the loading test platform, and the control algorithms were verified by the program.