1. Department of Electrical Engineering Southern Taiwan University Industry Application of Zero-Speed Sensorless Control Techniques for PM Synchronous Motors Student: Jia-Je Tsai Adviser: Ming-Shyan Wang Date : 10th-Dec-2008 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 37, NO. 2, MARCH/APRIL 2001 Alfio Consoli, Fellow, IEEE, Giuseppe Scarcella, Member, IEEE, and Antonio Testa, Member, IEEE

2. Department of Electrical Engineering Southern Taiwan University 2 Outline Abstract I. INTRODUCTION II. SENSORLESS CONTROL OF PMSM DRIVES III. A SIMPLE SENSORLESS TECHNIQUE IV. ROTOR POSITION DETECTION AT STANDSTILL V. EXPERIMENTAL RESULTS VI. CONCLUSIONS VII. REFERENCES

3. Department of Electrical Engineering Southern Taiwan University 3 Abstract This paper presents the state of the art in the area of industrial applications of sensorless control for permanent-magnet synchronous motor (PMSM) drives. Based on high-frequency signal injection, it is possible to achieve zero-speed operation without increasing the complexity and the cost of the system. The paper focuses on the practical implementation of one of the previously described high-frequency injection techniques in both salient and nonsalient PM machines.

4. Department of Electrical Engineering Southern Taiwan University 4 INTRODUCTION INTRODUCTION PMSM drives are today gradually replacing classic dc drives in a large number of industrial applications, taking full advantage of key features of PM motors, such as compactness, efficiency, robustness, reliability, and shape adaptation to working environment. PMSM drives need a relatively expensive position transducer to correctly align the current vector. Sensorless techniques generally estimate the rotor position by processing electrical motor variables, such as phase currents or stator voltages.

5. Department of Electrical Engineering Southern Taiwan University 5 INTRODUCTION INTRODUCTION The simplest PMSM sensorless techniques are based on rotor-flux-position estimation, by integration of the back EMF, but it fails at low and zero speed. A simple sensorless technique following such an approach is presented in this paper. It properly works at any speed, ranging from zero to the rated value, and can be applied to both salient and nonsalient machines. It does not require the knowledge of any motor parameter, while it allows low- cost implementation, requiring only current sensors already included in standard drives.

6. Department of Electrical Engineering Southern Taiwan University 6 SENSORLESS CONTROL OF PMSM DRIVES By neglecting hysteresis and eddy-current losses, the model of a cageless interior PMSM (IPMSM),written in a d-q rotor reference frame, with the d axis aligned with the direction of the PM flux, as shown in Fig. 1, is

7. Department of Electrical Engineering Southern Taiwan University 7 SENSORLESS CONTROL OF PMSM DRIVES Fig. 1. Vector diagram of a PMSM.

8. Department of Electrical Engineering Southern Taiwan University 8 SENSORLESS CONTROL OF PMSM DRIVES It is assumed that in an IPMSM owning a salient magnetic structure, while in a surface-mounted PMSM (SPMSM) owning a nonsalient magnetic structure. As it is possible to observe from (6), in a PMSM the torque depends on both the amplitude of the stator current vector and by the torque angle, defined as the angular displacement of the current vector from the d axis.

9. Department of Electrical Engineering Southern Taiwan University 9 A SIMPLE SENSORLESS TECHNIQUE In this paper, a simple but effective zero-speed sensorless technique for PMSM drives is presented. Compared with other techniques based on high-frequency signal injection, the proposed sensing shows lower sensitivity to noise, higher resolution. A high-frequency stator voltage component and on a suitable demodulation of the generated stator current component. In IPMSMs a maximum of the current amplitude occurs when the voltage vector is aligned with the maximum inductance axis and a minimum occurs when the voltage vector is aligned with the minimum inductance axis.

10. Department of Electrical Engineering Southern Taiwan University 10 A SIMPLE SENSORLESS TECHNIQUE Assuming an IPMSM supplied only with the 600-Hz additional voltage component, the mathematical model of the machine gives where expressed in electrical radians are respectively, the angular position of the d axis and of the additional 600-Hz voltage vector.

11. Department of Electrical Engineering Southern Taiwan University 11 A SIMPLE SENSORLESS TECHNIQUE From the previous equations at zero rotor speed it is possible to obtain the following steady-state expression: where

12. Department of Electrical Engineering Southern Taiwan University 12 A SIMPLE SENSORLESS TECHNIQUE IPMSMSPMSM of Phases33 Back EMF[V/Krpm]45 Rated Power[kW].75.69 Pole Pairs33 Rs.71.3 Ld[mH]5.43.3 Lq[mH]9.23.3 Max speed[rpm]3000 TABLE I PMSM PARAMETERS Substituting in (9) the parameters of an actual IPMSM, as reported in Table I. At frequencies higher than 400 Hz, (9) can be reduced to

13. Department of Electrical Engineering Southern Taiwan University 13 A SIMPLE SENSORLESS TECHNIQUE According to such an hypothesis, as shown in Fig. 2, minimum points of occur at and maximum points at The position of the d axis can be easily obtained from, which is known. The sampling time Fig. 2. Proposed rotor position estimation technique in a IPMSM

14. Department of Electrical Engineering Southern Taiwan University 14 A SIMPLE SENSORLESS TECHNIQUE Rotor speedT s (pp=2)T s (pp=3) 0rpm416 1000rpm441454 2000rpm469500 -1000rpm395385 -2000rpm375357 TABLE II ROTOR POSITION SAMPLING TIME

15. Department of Electrical Engineering Southern Taiwan University 15 A SIMPLE SENSORLESS TECHNIQUE Fig. 3. Implementation of the proposed technique has been settled to 15 V by trials, obtaining an experimentally evaluated efficiency reduction of less than 1% at rated power.

16. Department of Electrical Engineering Southern Taiwan University 16 The approximation introduced in (10) causes a small constant phase error between and A SIMPLE SENSORLESS TECHNIQUE

17. Department of Electrical Engineering Southern Taiwan University 17 ROTOR POSITION DETECTION AT STANDSTILL According to the proposed technique, the estimated position shows an uncertainty of electric degrees. In order to solve such uncertainty, the rotor can be initially placed in a known position by injecting a dc current. A dc current pulse is injected along the d axis, zero torque is generated, avoiding any shaft motion.

18. Department of Electrical Engineering Southern Taiwan University 18 ROTOR POSITION DETECTION AT STANDSTILL The injected current and the magnet flux own the same sign, the saturation level will increase, as well as the saliency and the amplitude of the high- frequency current component as the Fig. 5.

19. Department of Electrical Engineering Southern Taiwan University 19 ROTOR POSITION DETECTION AT STANDSTILL Fig. 6. and 7. show the envelope of experimentally recorded when a current test signal is injected, having, respectively, the same and the opposite sign of the rotor flux.

20. Department of Electrical Engineering Southern Taiwan University 20 ROTOR POSITION DETECTION AT STANDSTILL

21. Department of Electrical Engineering Southern Taiwan University 21 EXPERIMENTAL RESULTS The first is based on a 0.75-kW six-pole IPMSM, whose parameters are reported in Table I. (Figs. 8-13) The second prototype is based on a 0.69-kW six-pole SPMSM, whose parameters are also reported in Table I.

22. Department of Electrical Engineering Southern Taiwan University 22 EXPERIMENTAL RESULTS the output of a 1024-pulses-per-round encoder.

23. Department of Electrical Engineering Southern Taiwan University 23 EXPERIMENTAL RESULTS

24. Department of Electrical Engineering Southern Taiwan University 24 EXPERIMENTAL RESULTS

25. Department of Electrical Engineering Southern Taiwan University 25 EXPERIMENTAL RESULTS

26. Department of Electrical Engineering Southern Taiwan University 26 EXPERIMENTAL RESULTS

27. Department of Electrical Engineering Southern Taiwan University 27 EXPERIMENTAL RESULTS According to Table II, at zero speed in Fig. 13 we have a rotor position sampling time of 416, thus allowing good accuracy.

28. Department of Electrical Engineering Southern Taiwan University 28 EXPERIMENTAL RESULTS Fig. 14 shows a shaft position control test in which the reference is changed from 0 to 2 rad and back to 0.

29. Department of Electrical Engineering Southern Taiwan University 29 EXPERIMENTAL RESULTS

30. Department of Electrical Engineering Southern Taiwan University 30 EXPERIMENTAL RESULTS

31. Department of Electrical Engineering Southern Taiwan University 31 EXPERIMENTAL RESULTS

32. Department of Electrical Engineering Southern Taiwan University 32 EXPERIMENTAL RESULTS

33. Department of Electrical Engineering Southern Taiwan University 33 CONCLUSIONS It has been shown that the proposed technique can be used either in IPMSMs, owning a salient magnetic structure, or in SPMSMs and dc brushless motors, that own a nonsalient structure. The proposed technique features wide speed operating range, from zero up to the rated speed, wide position estimation bandwidth, that allows for either speed and position control, and good accuracy. Although sufficient for vector and speed control, the resolution obtained at the present is not sufficient for servo applications. However, no theoretical limits prevent to reach higher resolutions by improving the practical implementation of the proposed sensorless technique, which, in this paper, has been mainly oriented to low-cost applications.

34. Department of Electrical Engineering Southern Taiwan University 34 REFERENCES [1] E. K. Kenneth, A. C. Liew, and T. A. Lipo, “New observer-based DFO scheme for speed sensorless field-oriented drives for low-zero-speed operation,” IEEE Trans. Power Electron., vol. 13, pp. 959–968, Sept. 1998. [2] A. Consoli, A. Musumeci, S. Raciti, and A. Testa, “Sensorless vector and speed control of brushless motor drive,” IEEE Trans. Ind. Electron., vol. 41, pp. 91–96, Feb. 1994. [3] R. Dhaouadi, N. Mohan, and L. Norum, “Design and implementation of an extended Kalman filter for the state estimation of a permanent magnet synchronous motor,” IEEE Trans. Power Electron., vol. 6, pp. 491–497, Sept./Oct. 1994. [4] M. Schroedl and T. Stefan, “New rotor position detector for permanent magnet synchronous machines using the “INFORM” method,” Eur. Trans. Elect. Power Eng., vol. 1, no. 1, pp. 47–53, 1991.

35. Department of Electrical Engineering Southern Taiwan University 35 Thanks for your attention