Realization Of Low-speed Control Strategy Of Sensorless Switched Reluctance Motors

Compared with traditional motors,switched reluctance motors(SRM)have the advantages of simple structure and excellent speed regulation performance.However,the position sensors on the SRM cause some problems such as increased cost and reduced reliability.Therefore,in recent years,the industry has extensively studied low-speed control strategies related to sensorless switched reluctance motor,especially the pulse injection method.However,if using the pulse injection method,it is difficult to accurately detect the peak value of the pulse current.And it ignores the effect of the magnetic saturation effect,which results in a certain error in the judgment of the rotor position and affects the stable operation of the motor.Aiming at the above problems,this thesis implements a low-speed control strategy of sensorless SRM with high accuracy for rotor position detection..First,this article introduces the implementation principle of the pulse injection method and determines the selection range of the pulse injection method parameters.Next,this thesis analyzes the possible error sources and error ranges of rotor position detection under pulse injection method.The result shows that magnetic saturation which effects the influence of phase threshold and AD sampling accuracy limit are the main sources of error.Next,to solve the limitation of AD sampling accuracy,a dual-channel sampling circuit is proposed in hardware,and a peak fitting algorithm is proposed in software.By fitting the sampling current,the true pulse current peak size and the time of occurrence are predicted and it increases peak current detection accuracy.the saturation inductance modeling method is proposed for the magnetic saturation effect.From the Fourier series expression of the inductor,the actual commutation angle corresponding to the threshold inductance under different chopping currents is obtained to reduce the influence of the magnetic saturation effect.Then,a complete control strategy is proposed.It includes determining the magnetic saturation of the inductor at this time according to the excitation phase chopping current,obtaining the magnetic saturation effect error from the modeled inductor data,and fitting the sampled value obtained by the sampling circuit to determine the actual rotor position.Finally,based on the SRM low-speed control strategy simulation and actual measurement platform proposed in this paper,the feasibility of the proposed sensorless SRM low-speed control strategy is verified based on the comparison between simulation and actual measurement.The actual measurement results show that the sensorless SRM control strategy implemented in this thesis can make the motor run stably under low-speed operating conditions.The steady-state speed regulation range of the motor is 400-1700r/min,and the maximum output torque of the motor is 1.52 N·m,The rated power is 1100 W,and angle detection error is betwwen 1.54° and 1.94°,which basically achieves the expected design requirements proposed in this thesis.