Adaptive Filtering Based Position Sensorless Control Strategy For Synchronous Reluctance Motor Drives

The synchronous reluctance motor(Syn RM),whose rotor is made of iron without permanent magnets,makes use of the difference of magnetic resistance between the d and q axes to generate the electromagnetic torque,which significantly improves the performance-price ratio.As a result,it has been widely concerned by more and more scholars all around the world.In the Syn RM vector control system,the accurate rotor position information is the key to realize decoupling control of excitation current and torque current.The installation of position sensor leads to higher system cost,lower reliability and less anti-interference ability,so the sensorless control strategies of Syn RM have been paid more and more attention recently.The nonlinear effects of the inverter such as dead time and inherent characteristics of switching devices cause the output voltage of the inverter to be distorted,which in turn leads to the harmonic distortion of the current,and ultimately to an increase in torque ripple,and the performance of the system is hence decreases.Therefore,how to effectively suppress the nonlinear effects of the inverter and improve the reliability of the control system is of great si gnificance.Firstly,the mathematical models of Syn RMs in abc three-phase stationary reference frame,αβ two-phase stationary reference frame and dq two-phase rotating reference frame are respectively given.In addition,on basis of the principle of SVPWM,the simulation model is built according to the mathematical model of Syn RM.The model adopts the speed/current double closed-loop structure and SVPWM modulation,which can be utilized to realize the vector control of the Syn RM under ideal conditions(ignoring the nonlinear effect of the inverter).For sensorless control strategy of the Syn RM applied to the middle and high speed range,a rotor position fundamental frequency model-based on the extended electromotive force(EEMF)is adopted to realize the sensorless control of the drive system.Aiming at the chattering phenomenon of the traditional sliding mode observer(SMO),the improved SMO uses a continuous sinusoidal saturation function to replace the discontinuous sign function,which can significantly improve the chattering problems.The quadrature phase-locked loop(PLL)position tracker is designed to process the EEMF information obtained by the SMO,and then the rotor position information can be known,which effectively reduces the position estimation error.The corresponding simulation model is built to verify the improved SMO based sensorless control of Syn RM.In view of the nonlinear effects of the inverter,the(1±6k)th harmonics of the stator currents in the αβ two-phase stationary reference frame are caused,which in turn cause the(±6k)th harmonics of the stator current in the dq two-phase rotating reference frame,and finally the output torque of the motor generates(±6k)th pulsation.A Least Mean Square(Least Mean Square,LMS)adaptive linear neuron(ADAptive LInear NEuron,ADALINE)filtering method is proposed to achieve the suppression of torque pulsation.ADALINE has band-stop characteristics for the specific harmonic components of input signal,and multiple ADALINE filters based on the LMS algorithm are used to extract the(±6k)th harmonics of the d and q-axis currents,and then,the(±6k)th harmonics are eliminated by current feedback loop.Ultimately,the ripple of the output torque gets reduced and the performance of the Syn RM drive can be improved.A simulation model considering the nonlinear effects of the inverter is built to verify the effectiveness of the ADALINE filter based on the LMS algorithm in suppressing the ripple of the output torque.Finally,the sensorless Syn RM drive is applied on the STM32F103 VB based converter,and the experimental verification is carried out on the 3k W Syn RM platform.The experimental results proves the improved SMO based on sine saturation function is obviously able to improve the chattering problems of the traditional SMO in the sensorless Syn RM drive based on SMO,which proves the effectiveness of the improved SMO;The ADALINE filter based on the LMS algorithm can obviously suppress the(±6k)th harmonics in the d and q axis currents and the output torque,which proves the effectiveness of the ADALINE filter.