Sensorless speed control of nonsalient permanent magnet synchronous motor using rotor position tracking PI controller

Jong-Kun Lee, Jul-Ki Seok, Dong-Choon Lee
2004 IEEE 35th Annual Power Electronics Specialists Conference (IEEE Cat. No.04CH37551)  
Abslracf-This paper presents a new velocity estimation strategy of a non-salient permanent magnet synchronous motor (PMSM) drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system that has the information of rotor position error. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error to zero. For zero and Ion speed operation, PI
more » ... of rotor position tracking controller has a variable structure according to the estimated rotor velocity. Then, in zero speed, the rotor position and velocity has a sluggish dynamics because the varying gains are very low in this region. In order to boost the bandwidth of PI controller in zero speed, a loop recovery technique is applied to the control system. The experimental results show the satisfactory operation of the proposed sensorless slgorithm under load conditions. , INTRODUCTION The first generation of sensorless control on PMSM is based on rotor flux orientation by integration of back electromotive force (EMF) [I]- [3]. These approaches need the motor electrical parameters and fail to operate at low and zero speed since the information of back-EMF is too low. Recently, there are simpler and more effective algorithms are developed: high frequency injection method and constant frequency pattern method [4], [5]. The high frequency injection method uses the impedance difference of motor and can obtain the position information even at low and zero speed [4]. The non-salient PMSM originally has very small magnetic saliency or d-q axis impedance difference. In order to amplify this difference, in this study, the magnihide and frequency of the high frequency voltage signal are 100 V and 850 Hz for PMSM with 180 Vrms of rated voltage. Thus, this may cause undesirable side effects such as large harmonic losses, and acoustic noise. The overhead of injection voltage makes poor utilization of the drive and thus the high frequency injection method for non-salient PMSM is not matched. In addition, the high frequency excitation scheme usually requires a special signal processing technique and also limits the upper speed range below few hundred Hz due to extraction of injected signal. In constant frequency pattern method [5], the speed is estimated by processing the output voltages 01' d-axis synchronous PI current regulator in high speed range and the current with a constant magnitude and a pre-patterned frequency is injected from standstill to medium speed range. http://yu.ac.kr/-yupcl The open loop operation in low speed region maintained until a given speed at which the rotor position estimate is sufficiently accurate. The performance of the open loop control is heavily dependent on the selection of reference speed curve and the setting of ratio of voltage to frequency [6] . This selection procedure can be quite a tedious job to find the best operating conditions fitting their needs, which may be undesirable in an industrial sense. In addition, it needs an extra transition algorithm between two different control schemes and cannot perform the vector control in low and medium speed region. There is no guideline of sensorless PI controller gain setup or tuning, which decides the positiodvelocity estimation and closed loop control performance. Then, it relies too much on the inmition and experience of the designer, in order to get the best fit for the specific applications. This paper presents a new velocity estimation strategy of a non-salient PMSM with sinusoidal back-EMF without high frequency signal injection or special PWM pattern. This approach is based on the d-axis synchronous current regulator output voltage which includes the information of rotor position error. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error to zero. For zero and low speed operation, PI gain of rotor position tracking controller has a variable structure according to the estimated rotor velocity. Then, in zero speed, the rotor position and velocity has a sluggish dynamics because the varying PI gains are very low in this region. In order to boost the bandwidth of PI controller around zero speed, a loop recovery technique is applied to the control system. Analyzing this control system by the frequency domain specification such as phase margin and bandwidth assignment, the PI tuning formulas are also derived. The developed algorithm has been implemented on actual 600W PMSM drive system. The obtained results confirm the effectiveness of the proposed scheme. 11. ANALYSIS OF PROPOSED SENSORLESS CONTROL IN FREQUENCY DOMAIN The information of rotor position error can be extracted ftom the d-axis synchronous current regulator output voltage,
doi:10.1109/pesc.2004.1355187 fatcat:itun27qiq5blxn4m2acnmoryw4