Research On Sensorless Control Technology Of Switched Reluctance Motor At Low Speed

Switched reluctance motor(SRM)is widely used in high-speed operation and harsh working environment because of its many fault-tolerant capabilities,wide speed range,low environmental dependence,ruggedness and low cost,which highly recognized by the academic community.Research on position sensorless control can further expand the application field of switched reluctance motors,reduce the difficulty of equipment installation and maintenance,achieve cost savings and reduce system complexity,therefore,sensorless control has become a research hotspot.This article mainly analyzes and studies the sensorless control technology of the switched reluctance motor at low speed,the details are as follows:The technology of measuring the flux linkage of the switched reluctance motor is studied.The accurate acquisition of the electromagnetic characteristic curve can improve the accuracy of position detection in the sensorless control technology,based on the previous research,the existing rapid measurement technology of the magnetic flux characteristic curve is improved to establish the non-magnetic flux linear model.According to the geometric symmetry of the switched reluctance motor,turning on the single-phase or multi-phase winding can fix the rotor at multiple symmetrical positions.The voltage pulse method is used to measure the voltage and current of the phase winding at the symmetrical position,multiple flux linkage characteristic curves with symmetrical positions are combined,no additional hardware equipment is needed during the measurement process,and the use of voltage pulse method reduces the error caused by the heating phenomenon of winding and other parameters to the experiment.Based on the flux linkage curve of the symmetrical position,a high-order polynomial and fourier series are used to fit the flux linkage characteristic curve of other positions.Finally,a three-dimensional flux-current-position model is established.the simulation results and experimental waveforms are compared to verify the model applicability.Compared with the traditional measurement method,this method can obtain the flux characteristic curve of the entire cycle more quickly.The initial position estimation technology of switched reluctance motor is studied.Firstly,the principle of pulse injection method is analyzed,and the selection principles of pulse injection excitation time and injection frequency are introduced,so that the switching tube and other devices can operate normally in a safe working environment to ensure the feasibility of the experimental operation;then use pulse injection method to implement the average inductance partitioning of the switched reluctance motor,respectively study the position positioning of the motor at static and inertial speed,and finally verify the effectiveness of the inductance partitioning method through simulation and experiment.This method does not require additional hardware circuits,the control technology is simple,the operation is convenient,and it has strong universality and portability.The sensorless control technology based on single current threshold method is studied.When the motor is running at low speed,combined with the current chopping control and pulse injection method,the response current detected in the non-conducting phase winding is compared with the set current threshold to determine the commutation time,and then realize the position sensorless control of the switched reluctance motor.The relationship between bus voltage and current threshold is analyzed with the help of the flux linkage model,which provides a theoretical basis for the variable current threshold method and improves the robustness of the single current threshold position estimation technology.Choosing an appropriate current threshold can avoid the problem that the current peak at the time of commutation is not easy to detect due to the slow inductance change.The feasibility of the single current threshold position estimation technology is verified through simulation and experiment.This method is compared with the traditional dual current threshold method,it is more convenient and also has better position estimation accuracy.Finally,the single current threshold method is improved,the improved method only needs to add a current limit condition on the basis of the single current threshold method,and the calculation amount is small,so that the switched reluctance motor can smoothly transition from the static state to the low speed running state.The paper has 61 figures,6 tables and 99 references.